Dissertations / Theses on the topic 'Cyanide proces'

Ion exchange equilibria are presented for [ ]??? ??? Au(CN)2 / Cl , [ ]??? ??? Au(CN)2 / SCN and SCN??? / Cl??? in aqueous solution, and in various mixed solvents, at 303K using Purolite A500 as the ion-exchanger. The mixed solvents investigated include water-acetone, water-dimethylsulfoxide (DMSO) and water-N-methyl-2-pyrrolidone (NMP). In aqueous solution, the selectivity of Purolite A500 for a given anion increases in the order: [ ]??? ??? < ??? < Cl SCN Au(CN)2 . This selectivity sequence confirms the high affinity of the ion exchange resin for the [ ]??? Au(CN)2 species. In mixed solvents, however, the selectivity of Purolite A500 for [ ]??? Au(CN)2 decreases with an increase in the composition of the organic solvent in the external solution. Mixed solvents containing greater than 60 mol% organic solvent are preferred for the displacement of [ ]??? Au(CN)2 from the resin. The effectiveness of a given type of mixed solvent generally increases in the following order: DMSO &it acetone &it NMP. The ion exchange equilibria are correlated using the Law of Mass Action, modified with activity coefficients, to determine the equilibrium constant for each binary system. The fitted values of the equilibrium constants are consistent with the trends observed in the ion exchange isotherms. The accuracy of the correlation results in the mixed solvent systems range from 1 to 10% and this is similar to the level of accuracy obtained for the ion exchange equilibria in aqueous solution. From these results it can be concluded that the Law of Mass Action is equally valid in mixed solvent systems. The variation in the equilibrium constant with mixed solvent composition, for a given binary system, correlates well with the dielectric constant of the mixed solvent. For a given value of the dielectric constant, however, the equilibrium constant, however, the equilibrium constant is dependent on the type of mixed solvent. A fundamental relationship is derived between the equilibrium constants and the Gibbs energies of transfer associated with the solvation of the ions in the mixed solvents. Based on this relationship, the redistribution of ions between the pore solution and the bulk mixed solvent, appears to be the most significant factor that governs the selectivity of the resin in mixed solvent systems.

Thesis (MTech(Chemical engineering))--Cape Technikon, Cape Town, 2001
Over the years the carbon-in-pulp technology has been refined to become the highly efficient process that is used in our present-day system of recovering dissolved gold from cyanide leached pulps. The efficiency of a CIP circuit mainly depends on the effectiveness ofthe adsorption section as it not only determines the amount of soluble gold lost in the residues, but also indirectly affects the function of the other processes in the plant. Research in this area has declined over the past few years as a result of a decrease in the gold price. It is now more than ever important to investigate the operating conditions ofthe adsorption process to ensure that a highly effective system is maintained.The adsorption of gold cyanide onto activated carbon is to a large extent dependent on maintaining operating conditions well above those of equilibrium. The Freundlich and the Langmuir isotherms have been used by many researchers to describe the equilibrium conditions of the adsorption process. The general practice in the carbonin- pulp technology is to use an isotherm for the prediction of a circuit's performance. As confidence has increased in the reliability of these predictions, it has become important to acquire knowledge of the equilibrium condition that is driving the process. Previous research findings have indicated that the equilibrium isotherm of gold cyanide adsorption onto activated carbon is influenced by changes in the adsorption conditions down the adsorption train. This equilibrium or isotherm shift may lead to errors in the prediction of gold adsorption rates, which results in the filct that the simulations of the performance of the CIP circuits are not reliable. In this study the aim was to investigate the combined influence of various operating conditions on the adsorption equilibrium

Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2000
In a typical gold-recovery plant, it is estimated that a substantial amount of the gold in residues may be in the form that is recoverable by cyanidation. The gold in residues can be ascribed broadly to (l) the presence of cyanicides, which consume the cyanide radical and thus inhibit dissolution of gold, (2) refractory gold resulting from coatings on some gold particles, (3) large gold particles incompletely dissolved due to inadequate contact time, (4) unliberated gold as a result of too coarse a milled product, and (5) gold dissolved during leaching, then adsorbed by other minerals or by carbonaceous matter in the pulp. This study focuses on the latter, where dissolved gold is pregrobbed during leaching by adsorbent materials in the ore. The term pregrobbing refers to the active adsorption ofgold from cyanide pregnant solutions by components ofthe ore. It has been suggested that gold already dissolved by cyanide may be adsorbed by other minerals and by carbonaceous matter in the pulp. The presence ofcarbonaceous matter in gold ores presents a two-fold problem namely, the poor release of gold from the carbonaceous matrix and the uptake of dissolved gold by the carbonaceous leach residues. Studies by several other investigators using ores from various parts of the world have similarly shown that the natural carbonaceous matter associated with refractory gold ores often behaves like activated carbon when in contact with aurocyanide solutions. Some debate also exists over the extent to which gold may be adsorbed onto the surfaces of minerals. Different authors have identified that minerals such as' pyrite, copper sulphides, quartz and layered silicates, such as kaolin, phlogopite and ilIite exhibit gold adsorbing properties. Activated carbon was first used as a model pregrobber in batch kinetic adsorption experiments in the presence of a gold selective strong base anion-exchange resin.

Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2000
Due to equilibrium constraints and the relatively slow kinetics of the cyanidation of gold ores, calcium or potassium cyanide is added to the leaching stage in excess to that required theoretically. This, in many situations, result in large concentrations of free cyanide present in the effluent streams from gold plants. In view of the toxicity of cyanide and the fact that cyanide is fatal in small dosages, authorities have been forced to tigl1ten up plant discharge regulations. Therefore, it is vital to remove cyanide from industrial effluent, not only to meet standard requirements, but also to recover the cyanide as a means of reducing chemical costs. The aim of this study is to recover, rather than destroy, free cyanide from effluent streams via a metal impregnated carbon-in-column configuration. The first part of the study focused on the mechanism of free cyanide recovery by metal impregnated carbon and the factors influencing the kinetics of the process in a batch reactor. The second part concentrates on the optimisation of such a process m a column configuration, and subsequently to recover the cyanide from the carbon. In the batch experiments it was found that impregnated metal carbon outperformed virgin carbon for free cyanide removal both from a kinetic and equilibrium point of view. Furthermore: the presence of other metal cyanides in solution with free cyanide has a negligible effect on the performance of the metal (silver) impregnated activated carbon to remove free cyanide. Moreover, scanning electron micrographs revealed distinct differences in appearance of metal impregnated carbons, which ultimately responds differently to the removal of free cyanide. Although the kinetics of adsorption in the column experiments was found to be slower when compared to that experienced in a batch reactor, preliminary results show that a column configuration could be suitable for a free cyanide recovery on a large scale. Furthemore, a sensitivity analysis using the kinetics of adsorption and equilibrium cyanide loading as criteria, has been conducted on the column configuration. In these studies the effects of different bed volumes, competitive adsorption with other species present, different flow rates, different column diameters and initial cyanide concentrations on the process have been evaluated. These results were plotted as break-through curves, and the mass transfer zone (MTZ) was determined. It was found that impregnation in an air atmosphere yields a product with a higher capacity than in a nitrogen atmosphere, compromising carbon through combustion. Under a nitrogen atmosphere a more robust product is formed. As can be expected, lower linear velocities and/or larger bed volumes as well as lower initial free cyanide concentrations improve the fraction of cyanide removed in a column configuration.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The Platreef ore deposit, situated in the Bushveld Igneous Complex, is one of the world’s largest platinum group metal (PGM) resources. The mineralogy of this resource is, however, unique as it consists of complex PGM mineralization with mainly copper and nickel, at very low PGM grades. The PGMs are mainly present in the ore as slow floating refractory minerals resulting in marginal process economics when processing via traditional mill-float-smelt processes. A new process is currently being investigated to extract PGMs from low grade Platreef ore and concentrate using a sequential heap leach process entailing heap bioleaching and high temperature cyanide leaching. The heap bioleach extracts the base metals in an acidic sulphate medium using a mixed culture of mesophiles and thermophiles. After heap bioleaching, the heap will be reclaimed, rinsed and restacked for high temperature cyanide leaching where the cyanide liquor is directly heated via solar energy in panels. Platinum, palladium and gold are extracted during the cyanide leaching stage and then recovered from the pregnant liquor either by adsorption onto activated carbon or ion exchange resins. Final metal recovery will proceed by techniques such as electrowinning and precipitation. In this thesis, process options for the recovery of platinum group metals from cyanide solutions were identified with different flowsheet alternatives developed utilizing these options. Simulations were made for the different processing alternatives with the objective of finding the alternative flowsheet to maximise net present value. The various processing options were simulated, combining data from concurrent experimental studies and data reported in literature with kinetic adsorption models. This was combined with economic models to arrive at an optimum design for each flowsheet alternative. Seven different processing alternatives for the recovery of platinum group metals from cyanide solutions were developed and investigated. These included two different activated carbon flowsheets as well as five different ion exchange resin flowsheets. The flowsheets differ in the elution procedures as well as the use of single or multiple resins. The well-known Merrill Crowe precipitation process was investigated but was found to yield unsatisfactory results. In each alternative, the cyanide solution is sent to a SART (sulphidization, acidification, recycling and thickening) plant to remove copper, nickel and zinc from solution prior to upgrading by means of adsorption onto activated carbon or ion exchange resins and subsequent elution. The platinum group metals are recovered from the eluate by precipitation using an autoclave, producing a solid product consisting of base and precious metals, while gold is recovered by electrowinning. It was found that the overall performance of the resin-in-solution (RIS) flowsheets were superior to that of the carbon-in-solution (CIS) flowsheets, from an overall PGM recovery perspective and product grades. The superior adsorption kinetics and high selectivity of the resins for the PGMs resulted in excellent overall plant performances, with PGM extractions in excess of 97%. Gold extraction efficiencies with resins were found to be lower than those achieved in the CIS flowsheets, mainly due to the higher selectivity of the resins for the divalent platinum and palladium cyanide complexes and poor gold elution efficiencies. The gold concentrations in the feed streams to these processes were, however, very low, at only 8.5% of the total precious metal content. The overall precious metal recoveries of the RIS flowsheets were thus higher than the CIS flowsheets due to the superior PGM extractions. From the cost analyses performed it was found that the RIS flowsheets requires lower initial capital costs, almost 28% lower than that require for the CIS flowsheets, while the operating cost requirements were found to be ±10% lower. This, combined with the high overall precious metal extractions, resulted in the RIS flowsheets to achieve higher net present values than those of the CIS flowsheets over an assumed project life of 15 years. The optimum flowsheet proposed for the recovery of precious metals from cyanide leach solutions was a RIS flowsheet option that employed the Amberlite PWA 5 resin, capable of extracting platinum, palladium and gold from solution, with elution being performed with a zinc cyanide solution. This process option had the lowest capital and operating cost requirements while achieving similar overall precious metal recoveries as the other flowsheets. Economic analysis of this process yielded the highest net present value, with a 31% increase in the overall return on investment compared to the optimal CIS flowsheet. Based on this, it was concluded that resin technology would be the best process option for recovering precious metals from cyanide leach solutions, however, additional research is required as the current level of process development is only at a concept phase.
AFRIKAANSE OPSOMMING: Die Platrif-erts, geleë in die Bosveld Kompleks, is een van die wêreld se grootste platinum groep metaal (PGM) reserwes. Die mineralogie van hierdie reserwe is uniek en bestaan uit komplekse PGM mineralisasie met hoofsaaklik koper en nikkel, teen baie lae PGM inhoud. Die PGMe is hoofsaaklik teenwoordig in die erts as stadig drywende minerale en dit lei tot marginale ekonomiese uitsigte wanneer hierdie reserwe deur tradisionele metodes verwerk word. Tans word ʼn nuwe proses ondersoek om die PGMe vanuit lae graad Platrif-erts en konsentraat te ontgin deur gebruik te maak van ʼn sekwensiële hooploogproses wat uit ʼn bio-loog en hoë temperatuur sianied loog stappe bestaan. Die bio-loog stap is verantwoordelik vir die ontginning van die basis metale deur gebruik te maak van ʼn suur sulfaat medium bestaande uit ʼn gemengde kultuur van mesofiele en termofiele. Nadat die bio-hooploog stap voltooi is, word die hoop herwin, gewas en herpak vir die daaropvolgende hoë temperatuur sianied loog, waar die sianied oplossing direk verhit word deur die gebruik van son panele. Platinum, palladium en goud word tydens hierdie stap ontgin en kan dan herwin word vanuit die loog oplossing deur gebruik te maak van adsorpsie deur geaktiveerde koolstof of ioon-uitruilings harse. Finale metaal herwinning kan deur elektroplatering en presipitasie vermag word. In hierdie tesis word verskeie proses opsies vir die ontginning en herwinning van PGMe vanuit sianied loog oplossings ondersoek waarna verskeie proses vloei diagram alternatiewe ontwikkel is met die doel om die opsie te vind wat die hoogste netto ekonomiese waarde sal oplewer. Die verskillende opsies is gesimuleer deur gebruik te maak van eksperimentele data gepubliseer in die literatuur en dit te kombineer met kinetiese adsorpsie modelle. Dit was dan gekombineer met ekonomiese modelle om ʼn optimum ontwerp van elke proses te verkry. Sewe verskillende proses vloei diagramme vir die herwinning en ontginning van PGMe vanuit sianied loog oplossings is ontwikkel en ondersoek. Hierdie het twee verkillende geaktiveerde koolstof prosesse en vyf verskillende ioon-uitruilings hars prosesse beslaan. Die opsies het verskil van eluerings metodes en adsorpsie medium. Die alombekende Merrill Crowe presipitasie proses is ook ondersoek, maar daar is gevind dat hierdie proses oneffektiewe resultate oplewer met betrekking tot die herwinning van die drie edel metale. In elke alternatief word die sianied oplossing in ʼn SART proses verwerk, waar die basis metale herwin word, gevolg deur die opgradering van die edel metale d.m.v. geaktiveerde koolstof adsorpsie of ekstraksie m.b.v. ioon-uitruilings harse, gevolg deur eluering. Die PGMe word dan herwin vanuit die eluerings oplossing deur termiese degradering van die metaal sianied komplekse, wat ʼn hoë graad presipitaat lewer bestaande uit die basis en edel metale. Goud word herwin d.m.v. elektroplatering. Daar is bevind dat die algehele verrigting van die ioon-uitruilings hars opsies beter was as die van die geaktiveerde koolstof opsies, beide van ʼn algehele edel metaal herwinnings en produk suiwerheid perspektief. Die verhoogde adsorpsie kinetika en hoër PGM selektiwiteit van die harse het daartoe gelei dat uitstekende algehele PGM herwinning verkry is in hierdie opsies, meer as 97%. Goud ekstraksie deur die harse was laer as wat verkry was deur die geaktiveerde koolstof opsies, weens die hoër selektiwiteit van die harse vir die divalente platinum en palladium sianied komplekse en laer hars eluering effektiwiteit. Die goud konsentrasies in die voer strome na die prosesse was laag, en het sowat 8.5% van die totale edel metale uitgemaak, wat bygedra het tot die lae goud herwinning. Algeheel was die edel metaal herwinning van die hars prosesse beter as die van die koolstof prosesse a.g.v. die hoër PGM adsorpsie. Koste evaluerings van die verskillende vloeidiagramme het getoon dat die hars opsies laer kapitaal kostes benodig, omtrent 28% minder as die koolstof opsies, terwyl bedryfskostes omtrent 10% minder was. Dit het bygedra tot die feit dat die ioon-uitruiling hars opsies ʼn hoër algehele netto ekonomiese waarde oor ʼn projek leeftyd van 15 jaar sal hê, aangesien de PGM ekstraksie, en dus die jaarlikse inkomste, ook hoër was. Die algehele proses vloei diagram wat voorgestel is vir die herwinning van edel metale vanuit sianied loog oplossings is die hars opsie wat gebruik maak van die Amberlite PWA 5 hars, wat in staat is om platinum, palladium en goud terselfdertyd te absorbeer, gevolg deur die eluering van die hars deur die gebruik van ʼn sink sianied oplossing. Hierdie proses het die laagste kapitaal en bedryfskostes getoon terwyl algehele PGM herwinning om en by dieselfde was as al die ander opsies. Hierdie proses sal verder ʼn 31% verhoging in die opbrengs op belegging lewer in vergelyking met die optimum geaktiveerde koolstof opsie. Die algehele gevolgtrekking is dat hars tegnologie die beter opsie sal wees vir die herwinning van edel metale vanuit sianied loog oplossings. Addisionele navorsing is dus nodig om resultate te verbeter aangesien hierdie studie slegs op ʼn konsep fase benadering was.

This thesis explores the behaviour of metal cyanide complexes under oxidative acid conditions in ion exchange systems, with the objective of developing an ion exchange based process for the treatment of gold cyanidation tailings. The novel cyanide detoxification process developed from this study employs strong base ion exchange resins to extract cyanide from tailings. Variations in the stability of cyanide complexes are exploited to concentrate, recover, or destroy cyanide species loaded on the resin, through the use of an oxidative acid eluent containing H2O2 and H2SO4. This eluent removes all base metal cyanide complexes from strong base resins, while regenerating the resin. The spent eluent, containing the base metals recovered from the tailings, can be used as a source of such base metals. Copper can be recovered separately from other base metals if necessary. Low levels of precious metals present in the tailings are accumulated on the resin as the ion exchange bed is cycled between loading and elution stages. They can be recovered economically, so as to offset the cost of the tailings detoxification. Cyanide is initially concentrated as an alkaline solution, which can be detoxified within the process or recovered for recycling. This process was successfully tested at pilot scale by treating approximately 14,000 m3 of cyanide contaminated tailings solution, over 14 loading/elution cycles on a standard strong base ion exchange resin bed. This treatment reduced the total cyanide concentration of the contaminated solution from approximately 50 mg/L to an average of 1.5 mg/L. The reagent cost was approximately ADD 0.50 per m3 of treated liquor. When the resin was repeatedly loaded with mixed metal cyanide species and eluted with the oxidative acid eluent, a gradual deterioration of the ion exchange resin performance was noted. The reduction of net operating capacity of the columns due to resin deterioration was in the order of 1-3% per loading/elution cycle. The oxidation of resin catalysed by copper, the precipitation of metal hexacyanoferrates on the resin and the oxidation of Au(CN)2- to Au(CN)4- were identified as possible factors giving rise to the reduction of resin loading capacity.

Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 1999
Carbon-in-pulp (CIP) and carbon-in-leach (CIL) remain the most effective, and widely used processes for gold recovery from cyanided pulps. The extensive use of carbon in such processes have prompted many researchers to investigate the mechanism of metal cyanide adsorption. Not only has this provided many viable theories in the understanding of the mechanism, but it has also led to an improved understanding of the effects of the various operating conditions on the CIP circuit. However, the declining gold price has made gold producers aware of the need to either further optimise existing circuits or find alternative means of operation so as to improve efficiency. It is therefore the aim of this study to investigate the factors which influence the metal extraction circuit. In this study the effects of parameters such as gold and carbon concentrations, slurry density and stirring speed on the adsorption process were investigated. It was found that the effects of gold and carbon concentrations could be determined directly, that is, a definite linear relationship exists between these two parameters and adsorption rate. However, slurry density and stirring speed (power input) have a twofold effect on the process. For this reason two distinct terms called the "blinding" and "mixing" numbers have been identified. It has been shown that all the parameters investigated influences the rate of adsorption during the constant rate adsorption period. However, only solution concentration, carbon concentration and carbon loading influence the process during the diminishing rate of adsorption. This confirmed the belief that intraparticle diffusion is the rate controlling factor during the diminishing rate period. Furthermore, the point at which constant rate adsorption is replaced by the diminishing rate of adsorption is mainly a function of solution concentration.

Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2001.
Carbon-in-pulp technology is used extensively in the mining industry to recover metal cyanides from solution. Also this technology has found increasing application in the gold mining sector, replacing the less efficient zinc precipitation procedure. The extensive use of carbon in such processes have prompted many researchers to investigate the mechanism of metal cyanide adsorption. Not only has this provided many viable theories in the understanding of the mechanism, but has also led to an improved understanding of the effects of the various operating conditions on the ClP circuit. Also the modelling of this process has resulted in proposed rate equations of which the famous "kn" model is the most widely used in design. This is a single rate equation that could result in significant errors and hence a dual resistance model was developed. However this model is mathematically complex. Recently in an attempt to overcome the shortcomings of previous models, empirical calculations to accurately describe adsorption kinetics were developed at the Cape Technikon. These correlations were derived using batch experimental data. In this study the focus was on modeling the adsorption process on a continuous scale using a laboratory scale cascade system. This study utilized the fact that solution concentration is the main driving force for aurocyanide adsorption onto activated carbon and that carbon loading has an indirect effect on adsorption kinetics. The metal was ultimately tested against actual plant data and provided very accurate results.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.
Industrial wastewater management pertaining to the mining industry has become increasingly stringent, with companies being required to develop environmentally benign wastewater management practices worldwide. The industries that utilise cyanide compounds for the recovery of precious and base metals in a process known as the cyanidation process, have contributed substantially to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. Hence, a biotechnological approach was undertaken in this study to remediate free cyanide (CN-) and thiocyanate (SCN-), which are the major chemical contaminants which are normally found in cyanidation wastewaters. Furthermore, this biotechnological approach was investigated to understand the fundamental aspects of using this approach such that the information gathered can be utilized in pilot plant studies. Therefore, bioprospecting of potential CN- and SCN--degrading organisms was undertaken using two approaches; (i) culture-dependent approach and (ii) culture-independent approach. Using the culture-dependent approach, Pseudomonas aeruginosa STK 03, Exiguobacterium acetylicum and Bacillus marisflavi were isolated from an oil spill site and river sediment samples, respectively. STK 03 was evaluated for the biodegradation of CN- and SCN- under alkaline conditions. The organism had a CN- degradation efficiency of 80% and 32% from an initial concentration of 250 and 450 mg CN-/L, respectively. Additionally, the organism was able to degrade SCN-, achieving a degradation efficiency of 78% and 98% from non- and CN- spiked cultures, respectively. Furthermore, the organism was capable of heterotrophic nitrification but was unable to denitrify aerobically, with the autotrophic degradation of CN- by STK 03 being abortive.

Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: A 2 stage heap leach process to extract base and precious metals from the Platreef ore is currently being investigated industrially. A first stage bioleach is used to extract the base metals. In the 2nd stage, cyanide is used as the lixiviant at high pH to extract the platinum group metals and gold. By analogy with current gold recovery practices, the present study investigates the preferential and quantitative adsorption of precious metals (Pt, Pd, Rh and Au) over base metals (Cu, Ni and Fe) from an alkaline cyanide medium, by means of granular activated carbon. Experiments were designed statistically to optimise the process parameters using synthetic alkaline cyanide solutions close in composition to those expected from plant leach solutions. The statistical approach allowed the development of a reliable quantitative approach to express adsorption as a response variable on the basis of a number of experiments. A 2IV(7-2) fractional factorial design approach was carried out in a batch adsorption study to identify significant experimental variables along with their combined effects for the simultaneous adsorption of Pt(II), Pd(II), Rh(III) and Au(I). The adsorbent was characterized using SEM-EDX, and XRF. Precious metals adsorption efficiency was studied in terms of process recovery as a function of different adsorption parameters such as solution pH, copper, nickel, free cyanide ion, thiocyanate, initial precious metal (Pt, Pd, Rh and Au) ion and activated carbon concentrations. It was shown that adsorption rates within the first 60 minutes were very high (giving more than 90% extraction of precious metals) and thereafter the adsorption proceeds at a slower rate until pseudo-equilibrium was reached. Among the different adsorption parameters, at 95% confidence interval, nickel concentration had the most influential effect on the adsorption process followed by the adsorbent concentration. Adsorption of Ni was found to proceed at approximately the same rate and with the same recovery as the precious metals, showing a recovery of approximately 90% in two hours. The kinetics of Cu adsorption were slower, with less than 30% being recovered at the 120 minute period. This suggests that the co-adsorption of Cu can be minimised by shortening the residence time. Adsorption of Fe was found to be less than 5%, while the recovery of Rh was negligibly small. The effect of thiocyanate ion concentration was not as important as the effect of free cyanide ion concentration but still had some influence. The correlation among different adsorption parameters was studied using multivariate analysis. The optimum experimental conditions resulted in a solution with pH of 9.5, [Cu(I)] of 10 ppm, [Ni(II)] of 10 ppm, [CN ] of 132.44 ppm, [SCN ] of 98.95 ppm, [PMs] of 2.03 ppm and [AC] of 10 g/L. Under these conditions, predicted adsorption percentages of Pt, Pd and Au were approximately 98, 92 and 100%, at the level of 95% probability within two hours as an effective loading time. The negative values of ΔG° for all ions under optimum conditions indicate the feasibility and spontaneous nature of the adsorption process. Chemisorption was found to be the predominant mechanism in the adsorption process of Pt(II), Pd(II) and Au(I). Based on their distribution coefficients, the affinity of activated carbon for metal ions follows the selectivity sequence expressed below. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Finally, it is important that additional research and development activities in the future should prove the economic viability of the process. Future work is also needed to investigate the adsorption of precious metals (PMs) by comparing the efficiencies and kinetics of adsorption when using sodium hydroxide (in this study) or lime, respectively, in order to control the pH.
AFRIKAANSE OPSOMMING: ʼn Tweefasige hooploogproses vir die ontginning van basis- en edelmetale van die Platrif-erts word tans industrieel ondersoek. ʼn Eerstefase-bioloog word gebruik om die basismetale te ontgin. In die 2de fase word sianied gebruik as die uitloog by hoë pH om die platinum-groepmetale en goud te ontgin. Na analogie van hedendaagse goudherwinningspraktyke het die huidige studie die voorkeur- en kwantitatiewe adsorpsie van edelmetale (Pt, Pd, Rh en Au) bo basismetale (Cu, Ni en Fe) vanuit ʼn alkaliese sianiedmedium met behulp van korrelrige geaktiveerde koolstof ondersoek. Eksperimente is op statistiese wyse ontwerp om die parameters van die proses te optimaliseer deur van sintetiese alkaliese sianiedoplossings wat in hulle samestelling nou ooreenstem met dié wat van oplossings van plant-loog verwag word, gebruik te maak. Die statistiese benadering het die ontwikkeling van ʼn betroubare kwantitatiewe benadering om adsorpsie as ʼn responsveranderlike op grond van ʼn aantal eksperimente uit te druk, moontlik gemaak. ʼn 2IV(7-2) -Fraksionele faktoriale ontwerp-benadering is tydens ʼn lot-adsorpsiestudie gevolg om beduidende eksperimentele veranderlikes tesame met hulle gekombineerde uitwerkings vir die gelyktydige adsorpsie van Pt(II), Pd(II), Rh(III) en Au(I) te identifiseer. Die adsorbeermiddel is met behulp van SEM-EDX en XRF gekenmerk. Adsorpsiedoeltreffendheid van edelmetale is bestudeer ten opsigte van proseskinetika en herwinning as ʼn funksie van verskillende adsorpsieparameters soos oplossing-pH, koper, nikkel, vry sianiedioon, tiosianaat, aanvanklike edelmetaal (Pt, Pd, Rh en Au)-ioon en geaktiveerde koolstofkonsentrasies. Daar is aangetoon dat adsorpsietempo‟s binne die eerste 60 minute baie hoog was (het meer as 90% ekstraksie van edelmetale opgelewer) en daarna het die adsorpsie teen ʼn stadiger tempo voortgegaan totdat pseudo-ekwilibrium bereik is. Onder die verskillende adsorpsieparameters, by 95%-vertroubaarheidsinterval, het nikkel-konsentrasie die grootste invloed op die adsorpsieproses gehad, gevolg deur konsentrasie van die adsorbeermiddel. Daar is bevind dat die adsorpsie van Ni teen nagenoeg dieselfde tempo en met dieselfde herwinning as die edelmetale voortgegaan het, wat ná twee uur ʼn herwinning van nagenoeg 90% getoon het. Die kinetika van Cu-adsorpsie was stadiger, met minder as 30% wat teen die 120-minute-tydperk herwin is. Dit dui daarop dat die ko-adsorpsie van Cu tot die minimum beperk kan word deur verkorting van die verblyftyd. Daar is bevind dat die adsorpsie van Fe minder as 5% is, terwyl die herwinning van Rh onbeduidend klein was. Die uitwerking van die konsentrasie van die tiosianaatione was nie so belangrik as die uitwerking van die konsentrasie van vry sianiedione nie maar het steeds ʼn mate van invloed gehad. Die korrelasie tussen verskillende adsorpsieparameters is met behulp van meerveranderlike analise bestudeer. Die optimale eksperimentele toestande het gelei tot ʼn oplossing met ʼn pH van 9.5, [Cu(I)] van 10 dpm, [Ni(II)] van 10 dpm, [CN] van 132.44 dpm, [SCN] van 98.95 dpm, [EM‟e] van 2.03 dpm en [AC] van 10 g/L. Onder hierdie toestande was die voorspelde adsorpsiepersentasies van Pt, Pd en Au nagenoeg 98, 92 en 100%, op die vlak van 95%-waarskynlikheid binne twee uur as ʼn doeltreffende laaityd. Die negatiewe waardes van ΔG° vir alle ione onder optimale toestande dui op die uitvoerbaarheid en spontane aard van die adsorpsieproses. Daar is bevind dat chemiesorpsie die deurslaggewende meganisme by die adsorpsieproses van Pt(II), Pd(II) en Au(I) is. Gebaseer op hulle distribusiekoeffisiënte volg die affiniteit van geaktiveerde koolstof vir metaalione die selektiwiteitsvolgorde soos hieronder voorgestel. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Laastens, dit is belangrik dat addisionele navorsing en ontwikkelingsaktiwiteite in die toekoms die ekonomiese haalbaarheid van die proses bewys. Werk in die toekoms is nodig om die adsorpsie van edelmetale (EM‟e) te ondersoek deur vergelyking van die doeltreffendhede en kinetika van adsorpsie wanneer natriumhidroksied (in hierdie studie) of kalk, onderskeidelik, gebruik word ten einde die pH te beheer

Investigation of the NIR cyanine dye MHI-36 shows binding affinity to charged amino acids. This cyanine dye showed aggregation and dimer formation at higher dye concentration (2.0x10-3 M) induced by lysine. When dye concentration decreased to 1.0x10-4M no strong aggregate formation was viewed. Dye shows strong binding and selectivity properties towards charged amino acids lysine and arginine, compared to neutral leucine. It’s believed the positively charged presence was able to break and disrupt the conjugated π- π bonds at lower dye concentration. Computational work showed intramolecular aggregation of the phenyl groups on the dye. These aggregates are believed to create electron rich environment suitable for lysine interaction.

Thesis (PhD)--Stellenbosch University, 1992.
ENGLISH ABSTRACT: The dissolution of gold from refractory ores is a complex kinetic problem involving a number of chemical, mass transport and mineralogical factors. In most Witwatersrand ores in South Africa more than 97 % of the gold is dissolved in cyanide medium after a residence time of about 16 hours in pachuca tanks. This high percentage may be the reason why so little fundamental research has been done into the mechanism and kinetics of the leaching process. With the increasingly lower grades of ore mined, the introduction of backfill mining, and the reduction of profit margins, it has become imperative to increase the efficiency of gold dissolution. The effects of the chemistry and particle size on the dissolution of gold in each sample of ore were studied in detail. The emphasis in this study is on the effect of the leaching behaviour of various ore constituents on the rate of gold dissolution. Interferences with the leaching of gold in contact with other minerals or metals could be attributed to the galvanic interaction (electrical conductivity) between the gold and the mineral and to the formation of a surface film on the gold surface. Sulphide minerals and their oxidation products cause the largest decrease in gold dissolution rate. Galena enhances the rate of gold dissolution owing to dissolved Pb(II)-ions. Gold in contact with conductive minerals passivates as a result of the enhanced magnitude of the cathodic cu1Tent. In all experiments the rotating disc of gold passivated so that the rate of dissolution was much slower than that predicted by a mass-transport limiting model. The various films that form on the surface of the gold and associated minerals, as well as the galvanic interaction, depend largely on the pretreatment of the ore. Pre-elimination of host minerals from the gold bearing ore increases the dissolution rate of gold, and explains the kinetics of reaction on the gold surface to a large extent. The selective destruction of the various minerals with oxidative acid leaches destroys and/or decomposes certain minerals which may form films on the gold surface by precipitation. The chemical composition of these films and precipitates depends on the mineralogy of the sample. These films may be oxides, sulphides, carbonates and cyanide complexes. The complexes can be destroyed, depending on the nature of the film, by interstage dilute acid and/or cyanide washes in an agitated vessel. The destruction of the films exposes the gold surface for cyanidation. A simple distribution function similar to the King liberation model is proposed and tested to describe the dissolution step in the multi-step leaching mechanism. For the King model, good agreement is shown with experimental results. For the liberation results obtained by leaching in this study, the trend is co1Tect, but calibration is required for a close fit. A potentially important use for the liberation model by leaching is to predict the leachable or free gold in an ore from the free gold in the complete sample. This approach for studying the leaching behaviour of different gold bearing minerals has provided reasons why some ores leach better than others.
AFRIKAANSE OPSOMMING: Die loging van goud vanuit weerbarstige ertse is 'n komplekse kinetiese probleem wat verskeie faktore soos massa-oordrag, chemiese aspekte en mineralogiese ingeweefdheid insluit. Goud ekstraksies so hoog as 97 % in sianied oplossings in Pachuca reaktore na ongeveer 16 uur logingstyd word behaal in die meeste Witwatersrand ertse in Suid-Afrika. Hierdie hoë ekstraksies mag dalk die rede wees vir die min fundamentele navorsing oor die ekstraksie van goud vanuit minerale in 'n spesifieke erts. Die dalende erts grade, die verlaging van winsgrense en die terugplaas van geloogde erts in die myn noodsaak verbeterde goud ekstraksie. Verkeie faktore nl., chemie, diffusie, partikelgrootte en oplosbaarheid van goud in elke monster erts is in hierdie studie ondersoek. Die sentrale tema was om die logingsgedrag van goud vanuit verskeie minerale in 'n erts te bepaal. Galvaniese interaksie (hou verband met elektriese geleidingsvermoeë) en film vorming is die belangrikste faktore wat die loging van goud in kontak met minerale nadelig beïnvloed. Sulfied minerale en hul oksidasie produkte speel die grootste rol in die verlaging van die tempo van goudloging. Galena verhoog die tempo van goudloging as gevolg van die Pb (II)- ione in oplossing. Goud in kontak met geleidende minerale passiveer as gevolg van die verhoogde katodiese stroomdigtheid. In alle eksperimente met die roterende skyf (goudskyf) apparaat, passiveer die goudskyf in so 'n mate dat die logingstempo baie stadiger is as wat voorspel word met die massa-oordrags model. Die onderskeie films wat vorm op die goud- en geassosieerde minerale se oppervlaktes, asook die galvaniese interaksies, is 'n funksie van die voorafbehandeling van die erts. Die selektiewe eliminering van minerale vanuit 'n gouddraende erts verhoog die tempo van goudloging drasties en dit beskryf die kinetika van goudloging op die goudoppervlak in 'n groot mate. Die selektiewe eliminering van minerale deur gebruik te maak van oksiderende suurlogings, vernietig sekere van die minerale wat films op die goudoppervlakte kan veroorsaak deur middel van presipitasie. Die chemiese samestelling van hierdie films hang af van die mineralogie van die monster. Dit bestaan meestal uit oksiedes, sulfiedes, karbonate en sianiedkomplekse en hulle kan vernietig word deur middel van inter-stadia verdunde suur-en/of sianied wasse. 'n Eenvoudige distribusiefunksie, soortgelyk aan die King bevrydingsmodel word voorgestel en eksperimenteel getoets om die logingstap in die multi-stadia logingsmeganisme te beskryf. Vir bevryding deur loging, is die neiging van King se model korrek, maar kalibrasie word benodig vir goeie passing. 'n Potensiele gebruik van die aangepaste model is om vrye of loogbare goud in 'n spesi fieke partikel grootte fraksie van 'n erts te voorspel as die vry goud in die totale fraksie bekend is. Die resultate uit hierdie studie kan gebruik word om die logingsgedrag van gouddraende minerale te voorspel en te beskryf, en dus veduidelik hoekom goud uit sekere ertse beter loog as uit ander.

Thesis (MTech (Chemical Engineering))--Cape Technikon, 2000.
The large quantities of wood chips produced at mines from damaged underground timber contain gold that cannot be completely recovered by cyanidation. A fungus that can degrade a portion of the wood matrix will allow the gold that was previously locked up, to come into contact with the cyanide solution during beneficiation, thereby improving recoveries. The fungus Phanerochaete chrysosporium produces enzymes that use the organic compounds found in lignin as substrate. Consequently, the fungus is able to selectively break down lignin, which is one of the major components of wood. Chips sampled from Vaal Reef Mine contained between 2 and 5 mg/kg gold. The main source of gold in the chips was determined to be impregnated gold-bearing ore and discrete gold particles. Direct cyanidation resulted in around 60 per cent recovery prior to biological treatment. Despite relatively high weight losses caused to the chips as a result of treatment with Phanerochaete chrysosporium gold recovery only increased 10 per cent after 4 weeks treatment compared to direct recovery without treatment.

Cyanide (CN) is used in the gold mining industry to dissolve gold from free milling, complex and refractory gold containing ores. Processing sulphide containing refractory ores using biooxidation as a pre-treatment has become increasingly important due to the depletion of free milling ores. The reaction of CN with reduced sulphur species during the cyanidation process results in the formation of thiocyanate (SCN), often at relatively high concentrations (> 5 000 mg/L). The SCN and residual free CN are deported with the tailings as components of the liquid fraction. The concentration of SCN often exceeds the legislated discharge specification, necessitating on-site treatment, while water would also require treatment before on-site recycling and reuse. Biological degradation of CN and particularly SCN in these effluents provides an alternative to the more traditional processes such as SO2 treatment or UV destruction. The traditional destruction processes focus on breaking the chemical bonds, through physical or chemical means, thereby converting the toxic CN and SCN species to less toxic compounds. These processes generally suffer from high reagent cost, incomplete removal of CN and particularly SCN species and the generation of by-products which require further treatment. A number of microorganisms are capable of utilising CN and SCN as a source of sulphur, nitrogen and carbon, as well as generating energy from their oxidation. Additional removal of metal-CN complexes may be achieved by adsorption to the cell surface or extracellular polymeric substances secreted by the cells. The activated sludge tailings effluent remediation (ASTERTM) process was developed for the biological treatment of especially SCN, but also free CN and metal-cyanide complexes, such as CuCN and Zn(CN)2. The basic ASTERTM technology consists of an aerated reactor, in which SCN and CN species are oxidised and a settler to facilitate the recovery of water and potentially biomass. The desire to expand the commercial application of the technology necessitated a more complete, fundamental understanding of the ASTERTM process and required focused, in-depth research. This research aimed to define the viable operating window for SCN destruction, as well as optimising practical SCN and CN destruction process conditions. The ASTERTM process relies on a complex microbial community, so understanding the community structure and metabolic potential for SCN and CN destruction, further enhanced the fundamental and mechanistic understanding of this bioprocess. The research contributed to the fundamental understanding of this technology and enhanced the commercial application thereof. The first step in defining the operating window was to investigate the effect of feed SCN concentration on the SCN destruction ability of the mixed microbial community. Experiments were conducted at feed SCN concentrations ranging from 60- 1 800 mg/L. Complete SCN destruction was achieved across the range at ambient temperature. The maximum SCN destruction rate was 15.7 mg/L.h at an initial SCN concentration of 1 400 mg/L. Temperature was investigated in the range of 10-45°C with an initial SCN concentration range of 60-180 mg/L. A maximum SCN destruction rate of 17.4 mg/L.h was measured at 35°C, with an initial SCN concentration of 180 mg/L. A wide pH range (pH 5.0-10.0) was tolerated, with optimal performance recorded at pH 7.0. This evaluation identified not only the optimum operating pH, but also highlighted the negative impact of a sudden pH change on the efficiency of SCN destruction. Residual SCN concentrations below 1 mg/L were achieved in all cases, which would allow for discharge or recycling of treated water. Floc (sludge) formation was observed in experiments with high initial SCN concentrations and indicated a possible stress response during these batch experiments. Floc (sludge) formation were taken as microbial cells imbedded within extracellular polymeric substances and not only an aggregate of cells. Evaluating the maximum potential for SCN destruction and optimising the operating conditions and system configuration was investigated using continuous reactor experiments. A maximum SCN destruction rate of 87.4 mg/L.h (2 098 mg/L.d) was achieved at a feed SCN concentration of 1 000 mg/L and eight hour hydraulic retention time (HRT) during these experiments. The formation of substantial amounts of sludge was observed, with attachment to the reactor surfaces. The maximum feed SCN concentration, where substantial destruction was measured, was at 2 500 mg/L, achieving a practical SCN destruction rate of 972 mg/L.d. Significant inhibition of microbial inactivity was observed beyond this feed SCN concentration. The microbial community was able recover performance, within six days, after an extended period (54 days) of inactivity when the feed concentration was reduced from 3 500 mg/L SCN to 1 000 mg/L. The nature of the accumulated biofilm did not appear to change during the period of limited SCN destruction activity. Calculation of specific SCN destruction rates was not possible due to the nature of the sludge and heterogeneous dispersion of microbial members. Biomass (cells embedded in the EPS sludge) loading experiments showed SCN destruction rates increased with an increase in biomass loading, but this relationship was not proportional. A 25-fold increased biomass concentration resulted in only a 2-fold increase in destruction rate, suggesting a mass transfer limitation. The sludge most likely offers protection against unfavourable conditions, such as high residual SCN concentrations, by presenting a mass transfer barrier, resulting in an SCN concentration gradient across the sludge matrix. This enhances the robustness of the process and would facilitate rapid recovery in the case of a system upset at commercial scale. This research is the first to demonstrate the effective removal of SCN in the presence of suspended tailing solids, under conditions well suited for commercial application. The maximum SCN destruction rate achieved was 57 mg/L.h in the presence of 5.5% (m/v) solids. Sludge formation was not observed in the reactors containing solids, despite substantial sludge formation under similar operating conditions in the absence of solids, most likely due to shear-related effects. Fluctuations in pH, due to the nature of the solid material, were identified to negatively impact reactor performance and pH control was required. Moreover, the type of solid particle was found to influence the SCN destruction rate showing a need for adaptation not only to the presence of solids but also to various types of solids that are to be treated. Treatment of residual CN in solution is critical to ensure safe disposal or recycling of water. Treatment of SCN and CN was successfully demonstrated at feed concentrations up to 2 000 and 50 mg/L, respectively. The presence of residual CN (0.5 mg/L) prevented complete destruction of SCN, while complete SCN destruction was measured in the absence of CN under identical conditions. A range of reactor configurations were investigated and the optimum system required biomass retention, by means of attached biomass and complete destruction of any residual CN prior to SCN destruction. Conversion of SCN-S to SO4-S was stoichiometrically proportional in solution, while the majority of the liberated nitrogen appeared to be assimilated. Pre-colonisation of the reactor with attached biomass is beneficial and removed the need for a solid-liquid separation unit, reducing the potential footprint of the process. Additional treatment capacity could be created by operation of reactors in series. The diversity of the microbial community responsible for destruction of especially SCN were shown to be far more extensive than initially expected. Initial molecular characterisation of the microbial community selected for 185 representatives of bacterial 16S rRNA genes, of which 106 non-identical genotypes were sequenced. In contrast, for the reactor containing solids, only 48 representatives were selected and 30 genotypes were sequenced. Bacteria implicated in SCN destruction in the reactor containing suspended solids were members from the genera Bosea, Microbacterium and Thiobacillus. In the absence of solids, members capable of SCN destruction were identified from genera including Thiobacillus and Fusarium. High-throughput genome sequencing, followed by sequence assembly confirmed the dominance of Thiobacillus spp. Metabolic predictions indicated the autotrophs, gaining energy from the oxidation of reduced sulphur intermediates produced during SCN destruction were the dominant community members. The potential for ammonium oxidation and denitrification within the microbial community was identified during analysis of the metabolic potential, based on the metagenomic sequence data. These would be required for complete remediation of wastewater. The data generated during the research led to the development of a conceptual model to describe the evolution of system performance. Following inoculation with planktonic culture the SCN destruction is performed by the planktonic microbial community. An increased residual SCN concentration results in floc formation and the colonisation of reactor surfaces by attached biofilm. A concomitant decrease in planktonic cell concentration was observed, while SCN destruction rates increased. The extracellular material provided a matrix for biomass retention, resulting in high cell concentrations, and provided some protection against high SCN concentrations by providing a barrier to mass transfer. The attached biofilm developed to the point where overall SCN degradation rates may become limited by reduced oxygen penetration. The research presented in this thesis has been used to inform the design and operation of the ASTERTM process at commercial scale, specifically with respect to the benefits of attached biomass and the demonstration that the process can be used in the presence of suspended solids. The latter has been particularly important in applications where the available footprint is constrained.

Thesis (Ph. D.)--Georgia State University, 2006.
Title from file title page. Gabor Patonay, committee chair; Zhen Huang, Alfons Baumstark, committee members. Electronic text (236 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Jan. 28, 2008. Includes bibliographical references.

Los dos baños de cobre más utilizados comercialmente son el baño ácido a base de sulfato y el baño alcalino a base de cianuro. Los baños alcalinos son utilizados principalmente para producir recubrimientos en piezas con geometría compleja y para evitar la deposición galvánica cuando se deposita un metal en un sustrato menos noble. Debido a la toxicidad de los compuestos de cianuro, se han desarrollado baños alternativos usando diferentes agentes complejantes. El punto de partida de la presente investigación es un baño primario sin cianuros para deposición de cobre en sustratos de Zamak desarrollado en el Instituto de Investigaciones Tecnológicas del Estado de Sao Paulo / Brasil. La sustitución de materias primas como el cianuro debe ser económicamente ventajosa y técnicamente viable. De esta manera, la investigación presentada pretendió proponer una alternativa para el tratamiento de residuos líquidos del baño ya mencionado con la finalidad de recuperar de manera simultánea el agua y las materias primas en un sistema cerrado. Se ha estudiado el proceso de separación por membranas de intercambio iónico, la electrodiálisis, usando un sistema en escala de laboratorio y una disolución sintética que simulaba las aguas residuales del baño a base de HEDP. Se ha evaluado la viabilidad del sistema por medio del análisis de los parámetros de operación, como la extracción de iones, la tasa de desmineralización, el porcentaje de concentración, la eficiencia de la intensidad calculada para cada especie y el consumo medio de energía. Debido a que el ácido HEDP es un agente quelante, se ha evaluado el transporte de los quelatos Cu(II) HEDP a través de membranas de intercambio de aniones por medio de métodos electroquímicos. Se han construido curvas cronopotenciométricas y curvas intensidad-potencial para diferentes disoluciones sintéticas que contenían los mismos compuestos que el baño original. Se ha establecido la relación entre la presencia de los quelatos en las disoluciones y los grupos fijos de intercambio de aniones. Por fin, se han realizado las pruebas de deposición usando electrólitos conteniendo los compuestos reciclados y se han evaluado las características de los depósitos obtenidos. Los resultados indicaron que el sistema de electrodiálisis usando membranas de intercambio de aniones con grupos de intercambio de base fuerte ha podido producir disoluciones tratadas y un concentrado conteniendo los iones del baño. Se ha podido añadir el concentrado al baño original para compensar eventuales perdidas del arrastre sin afectar la calidad de los depósitos. Por lo tanto, la aplicación de la electrodiálisis demostró ser una alternativa viable para la recuperación del agua y de las materias primas de la disolución evaluada, reduciendo la generación de residuos líquidos y ahorrando los recursos naturales.
The two most common commercial copper baths are the acid sulfate copper bath and the alkaline cyanide copper bath. Alkaline copper baths are mostly used to coat parts with complex geometry and to avoid galvanic deposition when depositing a metal on a less noble substrate. Because of the toxicity of cyanide compounds, alternative baths have been developed using different complexing agents. The starting point of the present study is a cyanide free strike bath developed for copper plating on Zamak substrates developed by the Institute for Technological Research of the State of São Paulo/ Brazil. The replacement of a raw material such as cyanide must be economically advantageous and technically feasible. Therefore, this study intended to propose an alternative to the treatment of liquid wastes from the mentioned bath, aiming at simultaneous water reclamation and chemicals recovery in a closed system. The electrodialysis membrane separation process was studied, using a laboratory-scale system operating with a synthetic solution simulating the rinsing waters from the HEDP-based bath. The feasibility of the technique was evaluated by analyzing operational parameters such as ion extraction, demineralization rate, concentration rate, current efficiency for each anionic specie and average energy consumption. Because HEDP is a chelating agent, the transport of Cu(II) HEDP chelates through anion exchange membranes was also evaluated by means of electrochemical methods. Chronopotentiometric and current-voltage curves were constructed for different model solutions containing the same compounds as the original bath. A relation between the presence of chelates in the solutions and the fixed ion exchange group could be established. Lastly, deposition tests were performed using electrolytes containing the recycled inputs and the characteristics of the coatings were analyzed. The results showed that an electrodialysis stack using strongly basic anion exchange membranes was suitable to produce treated solutions and a concentrate containing the ions from the bath. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings. Thus, the application of electrodialysis was shown to be a feasible alternative for recovering water and inputs from the evaluated solution, reducing the wastewater generation and saving natural resources.
Els dos banys de coure més utilitzats comercialment són el bany àcid a base de sulfat i el bany alcalí a base de cianur. Els banys alcalins són utilitzats principalment per a produir recobriments en peces amb geometria complexa i per a evitar la deposició galvànica quan es deposita un metall en un substrat menys noble. A causa de la toxicitat dels compostos de cianur, s'han desenrotllat banys alternatius usant diferents agents complexants. El punt de partida de la present investigació és un bany primari sense cianurs per a deposició de coure en substrats de Zamak desenrotllat en l'Institut d'Investigacions Tecnològiques de l'Estat de Sao Paulo / Brasil. La substitució de matèries primeres com el cianur ha de ser econòmicament avantatjosa i tècnicament viable. D'aquesta manera, la investigació presentada va pretendre proposar una alternativa per al tractament de residus líquids del bany ja mencionat amb la finalitat de recuperar de manera simultània l'aigua i les matèries primeres en un sistema tancat. S'ha estudiat el procés de separació per membranes d'intercanvi iònic, electrodiàlisi, usant un sistema en escala de laboratori i una dissolució sintètica que simulava les aigües residuals del bany a base d'HEDP. S'ha avaluat la viabilitat del sistema per mitjà de l'anàlisi dels paràmetres d'operació, com l'extracció d'ions, la taxa de desmineralització, el percentatge de concentració, l'eficiència de la intensitat calculada per a cada espècie i el consum mitjà d'energia. Pel fet que l'àcid HEDP és un agent quelant, s'ha avaluat el transport dels quelats Cu (II)-HEDP a través de membranes d'intercanvi d'anions per mitjà de mètodes electroquímics. S'han construït corbes cronopotenciomètriques i corbes intensitat-potencial per a diferents dissolucions sintètiques que contenien els mateixos compostos que el bany original. S'ha establit la relació entre la presència dels quelats en les dissolucions i els grups fixos d'intercanvi d'anions. Finalment, s'han realitzat les proves de deposició usant electròlits contenint els compostos reciclats i s'han avaluat les característiques dels depòsits obtinguts. Els resultats van indicar que el sistema d'electrodiàlisi usant membranes d'intercanvi d'anions amb grups d'intercanvi de base forta ha pogut produir dissolucions tractades i un concentrat que conté els ions del bany. S'ha pogut afegir el concentrat al bany original per a compensar eventuals perdudes de l'arrossegament sense afectar la qualitat dels depòsits. Per tant, l'aplicació de l'electrodiàlisi va demostrar ser una alternativa viable per a la recuperació de l'aigua i de les matèries primeres de la dissolució avaluada, reduint la generació de residus líquids i estalviant els recursos naturals.
Scarazzato, T. (2017). Treatment of a cyanide-free copper electroplating solution by electrodialysis: study of ion transport and evaluation of water and inputs recovery [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/98502
TESIS

The two most common commercial copper baths are the acid sulfate copper bath and the alkaline cyanide copper bath. Alkaline copper baths are mostly used to coat parts with complex geometry and to avoid galvanic deposition when depositing a metal on a less noble substrate. Because of the toxicity of cyanide compounds, alternative baths have been developed using different complexing agents. The starting point of the present study is a cyanide-free strike bath developed for copper plating on Zamak substrates developed by the Institute for Technological Research of the State of São Paulo/ Brazil. The replacement of a raw material such as cyanide must be economically advantageous and technically feasible. Therefore, this study intended to propose an alternative to the treatment of liquid wastes from the mentioned bath, aiming at simultaneous water reclamation and chemicals recovery in a closed system. The electrodialysis membrane separation process was studied, using a laboratoryscale system operating with a synthetic solution simulating the rinsing waters from the HEDP-based bath. The feasibility of the technique was evaluated by analyzing operational parameters such as ion extraction, demineralization rate, concentration rate, current efficiency for each anionic specie and average energy consumption. Because HEDP is a chelating agent, the transport of Cu(II)-HEDP chelates through anion-exchange membranes was also evaluated by means of electrochemical methods. Chronopotentiometric and current-voltage curves were constructed for different model solutions containing the same compounds as the original bath. A relation between the presence of chelates in the solutions and the fixed ion exchange group could be established. Lastly, deposition tests were performed using electrolytes containing the recycled inputs and the characteristics of the coatings were analyzed. The results showed that an electrodialysis stack using strongly basic anion-exchange membranes was suitable to produce treated solutions and a concentrate containing the ions from the bath. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings. Thus, the application of electrodialysis was shown to be a feasible alternative for recovering water and inputs from the evaluated solution, reducing the wastewater generation and saving natural resources.
Os dois banhos de cobre comerciais mais comuns são o banho ácido à base de sulfato e o banho alcalino à base de cianeto. Os banhos alcalinos são usados principalmente para recobrir peças com geometria complexa e para evitar a deposição por deslocamento galvânico quando se deposita um metal em um substrato menos nobre. Por causa da toxicidade dos compostos cianídricos, banhos alternativos vêm sendo desenvolvidos usando diferentes agentes complexantes. O ponto de partida do presente estudo é um banho toque isento de cianeto para deposição de cobre em substratos de Zamak, desenvolvido pelo Instituto de Pesquisas Tecnológicas / Brasil. A substituição de matérias-primas como o cianeto deve ser economicamente vantajosa e tecnicamente viável. Desta forma, este estudo pretendeu propor uma alternativa para o tratamento de resíduos líquidos do banho mencionado, visando à recuperação simultânea da água e das matérias-primas em um sistema fechado. Foi estudado o processo de separação por membranas de eletrodiálise, usando um sistema em escala laboratorial operando com uma solução sintética que simulava as águas de lavagem do banho à base de HEDP. A viabilidade da técnica foi avaliada por meio da análise de parâmetros operacionais, como a extração dos íons, a taxa de dessalinização, o percentual de concentração, a eficiência de corrente calculada para cada espécie iônica e o consumo médio de energia. Devido ao HEDP ser um agente quelante, o transporte de quelatos Cu(II)-HEDP através de membranas aniônicas foi avaliado por meio de métodos eletroquímicos. Curvas cronopotenciométricas e curvas corrente-potencial foram construídas para diferentes soluções sintéticas que continham os mesmos compostos que o banho original. A relação entre a presença de quelatos nas soluções e os grupos fixos de troca iônica pôde ser estabelecida. Por fim, testes de deposição foram realizados usando eletrólitos contendo os compostos reciclados e as características dos depósitos foram analisadas. Os resultados mostraram que o sistema de eletrodiálise usando membranas aniônicas contendo grupos de troca fortemente básicos pôde produzir soluções tratadas e um concentrado contendo os íons do banho. O concentrado pôde ser adicionado ao banho original para compensar eventuais perdas por arraste sem afetar a qualidade dos depósitos. Assim, a aplicação da eletrodiálise se mostrou uma alternativa viável para a recuperação de água e de insumos da solução avaliada, reduzindo a geração de efluentes e economizando recursos naturais.

This master thesis is focused on theoretical study of the Cy3 and Cy5 dyes and their interactions with DNA. The main aim was to find the mot populated conformations of the Cy3-DNA and Cy5-DNA complexes. A comparison with the experimental structure was also done and the influence of the cyanine dyes on the conformational changes of the DNA chain was evaluated.

The experimental work described in this thesis is aimed primarily towards elucidation of the speciation of zinc-cyanide systems at elevated pH. In this study the formation and stability of H+-eN-, binary Zn2+-eN- and ternary Zn2+-CN--QH- complexes were studied by glass electrode potentiometry in aqueous solutions at 25.0°0 and in a medium of ionic strength of 0.1 mol dm-3. The solution pH was varied to cover the range 4 to 11. The study was undertaken with a view to establishing whether and under what conditions soluble binary zinc-cyanide complexes and ternary zinc-cyanide-hydroxide complexes form, and to determine formation constants for any such species that are found. This information would be useful in defining more precisely the speciation of solutions containing zinc and cyanide ions at elevated pH values. A titration method was used, in which hydrogen ion concentration was monitored by means of a glass indicating electrode. The cell was calibrated to allow measurements of hydrogen ion concentration rather than hydrogen ion activity. Owing to precipitation difficulties, the reagents were used at sub-millimolar concentration levels. The potentiometric data was interpreted with the aid of various formation function plots together with the use of various computer programs, such as HALTAFALL and ESTA. The results show that the ternary complex Zn(ON)3(OH)2- is formed in significant amounts in solutions of pH > 8.5. Some evidence was also obtained for the existence of the five coordinated species Zn(CN)3(OH)~- and Zn(CN)~- in these solutions, but existence of the latter two species cannot yet be regarded as firmly established. No polynuclear complexes were detected at the sub-millimolar concentrations used. Formation constants are reported for H+-eN- and both binary Zn2+-eN- and ternary Zn2+-eN--QH- species.
Thesis (M.Sc.)-University of Natal, Durban, 1990.

Please read the abstract in the front section of this document
Dissertation (M Eng (Metallurgical Engineering))--University of Pretoria, 2006.
Materials Science and Metallurgical Engineering
unrestricted

碩士
國立清華大學
化學系
103
Abstract Currently most of the fluorogenic probes are designed for the detection of enzymes which work by converting the nonfluorescence substrate into the fluorescence product via an enzymatic reaction. On the other hand, the design of fluorogenic probes for non-enzymatic proteins remains a great challenge. Herein, we report a general strategy to create near-IR fluorogenic probes, where a small molecule ligand is conjugated to a novel γ-phenyl-substituted Cy5 fluorophore, for the selective detection of proteins through a non-enzymatic process. Detail mechanistic studies reveal that the probes self-assemble to form fluorescence-quenched J-type aggregate. In the presence of target analyte, bright fluorescence in the near-IR region is emitted through the recognition-induced disassembly of the probe aggregate. This Cy5 fluorophore is a unique self-assembly/disassembly dye as it gives remarkable fluorescence enhancement. Based on the same design, three different fluorogenic probes were constructed and one of them was applied for the no-wash imaging of tumor cells for the detection of hypoxia-induced cancer-specific biomarker, transmembrane-type carbonic anhydrase IX.

碩士
國立中央大學
環境工程研究所
82
Ferric-Complexed Cyanide (FCC) which was resistant to destruction by conventional physichemical treatment technologies was found in various industrial wastes. The treatment feasibility study was conducted on FCC at high concentration by using different processes including High Temperature Hydrolysis (HTH), and Both processes. The experiments were operated under the following conditions: total reaction time 150 minutes, mixing rate 1300 rpm and excess air 20%. The reaction temperatures (180℃∼240℃) and hydrolysis time (0∼150 min.) were selected as the major factors in c COD, CN, and NH3 were analyzed to evaluate the treatment feasibility. The results indicated that HTH, WAO and the combined processes were found effective in the destruction of FCC at high concentrations. The total cyanide residues showed a sharp decrease in short time from the start of reaction in all treatments, and the HTH. In the decomposition of FCC, the HTH process produced ammonia and formic acid, while WAO yielded ammonia and carbonate. The results of T-test suggested that the possible main destruction mechanism of FCC was due to hydrolysis in the presence of water. Both HTH and WAO processes in the destruction of FCC appeared to be a first-order two steps reaction with respect to total cyanide. The activation energy analyzed by Arrhenius equation was found to be 47229J/ mole for HTH and 54964 J/mole for WAO process in the first step reaction .

A thesis submitted to the Faculty of Engineering and The Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering Johannesburg 12 September 2016
Comminution and leaching unit processes play a major role in extracting valuable minerals from ore. Most of the research reported in the literature has focused on optimising individual unit operations rather than on integrating the whole process. This thesis develops an integrated approach to mineral processing systems and flow sheets and is intended to create a methodology for process synthesis that can be applied throughout the extractive metallurgical industry. This could lead to improved efficiency in the overall process by obtaining optimum recovery and, most important, a reduction in energy and material costs. In order to illustrate the methodology a particular example was chosen, namely optimizing the joint comminution and leaching of a particular gold ore. In this investigation laboratory scale grinding and leaching profiles for a gold feed sample (1700–850 μm) were measured. In a laboratory mill various combinations of grinding media, filling level and ball size were investigated, and of the three ball sizes used (10, 20 and 30mm) breakage was most pronounced for the 20 mm. Thus for instance it was also established that when using a higher filling ( =30%) and a ball size of 30 mm, more energy was consumed but less liberation occurred, thus a lower amount of gold was extracted during a 24-hour leaching period. Finally, the breakage kinetics of the gold ore was looked at. Using a standard population model the breakage and selection function parameters were successfully calculated. An investigation into the dissolution kinetics of gold ore in a solution of NaCN was also done. These were found to depend on the stirring rate, reaction temperature, particle diameter and the concentration of the leachant. The rate increased with the stirring speed, reaction temperature and leachant concentration, but decreased when the particle size was greater. The activation energy for the dissolution was estimated at about 3 kcal/mol. Furthermore, the linear relationship between the rate constant and the reciprocal of the square of the particle size is a strong indication that the gold dissolution process is diffusion-controlled. The experimental results were well-fitted to a shrinking core model. In attempting to understand the results, the researcher carried out a number of experiments that involved an investigation into the relationship between comminution and leaching in terms of energy usage and particle size, the former to establish the most efficient application of energy, and the latter to identify the degree of fineness that would ensure optimal recovery. The Attainable Region (AR) method was then used to establish ways of finding the leaching and milling times required to achieve minimum cost (maximise profit). No work on utilizing the AR technique to minimise the cost of milling and leaching on a real industrial ore has previously been published. The investigation aims to show how the AR technique can be used to develop ways of optimising an industrial process that includes milling and leaching. The experimental results were used to show how this method could be successfully applied to identifying opportunities for higher efficiency when performing these operations. The approach however is general and could in principle be used for any two or more unit operations in determining how the product from one unit should be prepared to feed to the next unit so as to optimize the overall process.
MT2017

碩士
國立交通大學
應用化學系碩博士班
106
In this thesis, two novel fluorescent probes CyA and DNSC were synthesized for detecting cyanide and cysteine, respectively. CyA has been designed for cyanide detection. The process is based on nucleophile-attack by cyanide in the indolium group, resulting in fluorescence change. The probe CyA showed high sensitivity and selectivity for rapid detection of cyanide over other anion solution. The detection limit of CyA to cyanide is 1.05 µM. DNSC was a new cysteine fluorescence sensor, based on a two photon fluorophore, 3-hydroxychromeno[3,4-c]chromene-6,7-dione named as DC, and 2,4-dinitrobenzenesulfonyl moiety. While DNSC reacted with cysteine, the 2,4-dinitrobenzenesulfonyl moiety was cleaved and resulted in strong yellow fluorescence. DNSC showed high selectivity and sensitivity for detecting cysteine and homocysteine with detection limits 20 nM for cysteine, and 34 nM for homocysteine, respectively. Furthermore, we applied DNSC into biological experiments. DNSC showed very low cytotoxicity in HeLa cell, and can be used to detect the endogenous cysteine in HeLa cell.

The thesis entitled “New Supramolecular Ion Sensing Probes and their Application in the Detection of Environmentally Relevant Ions” deals with the design and synthesis of several small molecular probes which can specifically sense environmentally relevant ions of (anion or cation) particularly in aqueous or biological medium. The probes have been designed using four different molecular entities which include anthraquinone, oxidized bis-indolyl system, pyrene and rhodamine. The probes afford naked eye detection of a particular ion in the aqueous medium. This work has been divided into six chapters. Chapter 1. Introduction The first chapter gives a brief idea of ion sensor. It provides the description of various approaches used for designing molecular sensors. The chapter further presents an overview of the four different dyes (anthraquinone, oxidized-bis-indole, pyrene and rhodamine) used for designing probes in this work. The properties of these probes, their advantages and disadvantages to use as a signaling subunit have been discussed. This chapter also describes the use of micellar medium for solubilizing different organic dyes in water. Chapter 2. Colorimetric Probes based on Anthraimidazolediones for Selective Sensing of Fluoride and Cyanide ion via Intramolecular Charge Transfer. The second chapter describes the design and synthesis of four different probes based on anthra [1, 2-d] imidazole-6, 11-dione. The anthraquinone part of each molecule has an acceptor moiety whereas substituted nitrogen linked aromatic unit forms the donor site. Each probe acted as strong colorimetric sensor for fluoride and cyanide ion detection and exhibited intramolecular charge transfer (ICT) band which showed significant red-shifts after addition of either the F¯ or CN¯ ion. One of the probes 2 showed selective colorimetric sensing for both cyanide and fluoride ions. In organic medium 2 showed selective color change with fluoride and cyanide, whereas in aqueous organic medium it showed a selective ratiometric response towards cyanide ion. The effect of anionic charge (on the donor moiety) on ICT has been discussed. Among the various donor moieties, the donor site having negative charges on them was found to disperse greater electron density on them. Figure 1. Molecular structures of the sensors Chapter 3 deals with chemodosimetric detection of cyanide ion in water using various oxidized bis-indole based compounds. Chapter 3A. A Chemodosimetric Probe based on a Conjugated and oxidized Bis¬ indolyl System for Selective Naked Eye Sensing of Cyanide ion in Water. The chapter 3A describes the design and synthesis of a new water-soluble bis-indolyl based probe, 5 which possesses two –COOH groups. This probe specifically reacted with the CN¯ ion in pure water at ambient temperature and produced a remarkable change in color from red to colorless. The mechanism of this process was investigated by NMR (1H, 13C and DEPT-135) spectroscopy, mass spectrometry and kinetic studies. The mechanism investigation showed that the cyanide ion reacts with the probe and removes the conjugation of the bis-indolyl moiety of the probe with that of the 4-substituted aromatic ring which renders the probe colorless. Taken together a plausible mechanism of the reaction was presented which showed to operate via a Michael type adduct formation under ambient conditions of pH and temperature in water. The probe gave a detection limit of 0.38 ppm for detection of cyanide ion in water. Figure 2. Molecular structure of the probe 5. Chapter 3B. Micelle Assisted ppb level Detection of Cyanide ion in Water by Chemodosimetry and Visual detection of the Endogenous Cyanide. The chapter 3B deals with the synthesis of a bis-indole based colorimetric probe 6. The probe showed selective detection of the cyanide ion in water at ppb level and a visible detection of endogenous cyanide from cassava (a major staple food in the developing world) by chemodosimetry. The cyanide ion binds with the probe 6 in a chemodosimetric fashion and follows pseudo first-order kinetics in water under appropriate conditions. It showed a highly sensitive detection of the cyanide ion in water with a detection limit of 0.33 ppm. The use of the micellar medium improved the detection limit drastically and a ppb level detection limit was achieved. The probe also showed the detection of the endogenously bound cyanide in cassava both visually and by spectrophotometer. Figure 3. Molecular structure of the probe 6. Chapter 3C. Ratiometric Cyanide ion probe in Water and for the detection of the Endogenously bound cyanide. Chapter 3C presents the synthesis of two new bis-indolyl (7 and 8) based probes for colorimetric detection of cyanide ion in pure water. Compound 8 showed a ratiometric response with cyanide in water and a visual detection of the endogenously bound cyanide ion in cassava. Using compound 8 the selective detection of the cyanide ion in water was achieved with a detection limit of ~ 17 ppb which is almost 13 times lower than the permitted limit as specified by EPA, United States. 7; R = H 8; R = -(OCH2CH2)3CH3 Figure 4. Molecular structures of the probes 1 and 2. Chapter 4 deals with the colorimetric and ratiometric detection of the Cu2+and Hg2+ions using different small synthetic molecular probes. Chapter 4A. Colorimetric Sensors for Ratiometric Detection of Copper and Mercury ions in Biological media and below ppm level in Water. The chapter 4A deals with the synthesis of two novel colorimetric probes (9, 10) using bispicolyl unit as the binding moiety and anthraimidazolediones and bis-indolyl system as a signaling sub-unit. Using the two sensors, Cu2+ion can be detected below the permitted limit (1.3 ppm) in both drinking water and at physiological pH 7.4. Sensor 9 can detect both Cu2+and Hg2+ in water with very low detection limit. It showed specific binding with Cu2+ at physiological pH 7.4 and in presence of serum albumins. Chemosensor 10 can be used for the specific detection of both Cu2+and Hg2in water as well as for the contamination in microorganisms. Figure 5. Molecular structure of the sensors 9 and 10. Chapter 4B. A New Molecular Probe for the Selective Sensing of Cu2+ and Hg2+ ions in Micellar Media and in Live ells.This chapter describes a synthesis of a novel bispicolyl based sensor 11 which can detect Cu2+ ion specifically in water medium and both Cu2+ and Hg2+ ions selectivelyin Brij-58 micellar medium. In micellar medium both the ions can be detected in the ppb level. Using fluorescence spectroscopy these two metal ions can be discriminated.The probe is also be useful for checking metal ion contamination in cellular samples. Figure 6. Molecular structure of the sensor 11. Chapter 4C. Rhodamine based Sensors for Cu2+ and Hg2+ ions in Water and in Biological media. The chapter 4C presents the synthesis and the sensing properties of the three positional isomers of the pyridine end of the rhodamine-pyridine compounds (12-14). The three isomers only differ in the position of nitrogen of the pyridine moiety. Sensor 12, which contains the pyridine nitrogen at the ortho-position showed selective sensing toward Cu2+ ion in both pure water and in buffered physiological media of pH 7.4. It gave a detection limit of ~13 ppb which is 100 times lesser than the EPA permitted limit. The other two sensors 13 and 14, which possessed the pyridine ends with the nitrogen atom at the meta- and the para- positions respectively showed the selective sensing of Hg2+ ion in water and did not show any interaction with the Cu2+ ion. Probes 2 and 3 showed ‘turn-on’ detection of Hg2+ ion both in the UV-vis and the fluorescence emission spectroscopy. Compound 2 and 3 showed a detection limit of ~ 9 and 4 ppb respectively. The NMR titration showed the change in color was due to the opening of the spirolactam ring of the rhodamine. The sensors can also be used for the detection of Cu2+ and Hg2+ ion in real life water samples and in the live cells. Figure 7. Molecular structure of the sensors 12, 13 and 14. Chapter 5. Ratiometric and ppb level Detection of Toxic Transition Metal ions using a Single Probe in Micellar media. This chapter describes the selective sensing of multiple ions using a single probe 15. The probe incorporates pyrene and pyridine as signaling and interacting moiety respectively. The sensor showed different responses towards different metal ions just by varying the medium of detection. In organic solvent (acetonitrile), the probe showed selective detection of Hg2+ ion. In water the fluorescence quenching was observed with three metal ions, Cu2+, Hg2+ and Ni2+. Further just by varying the surface charge of different micellar media, the probe showed selective interaction with Hg2+ ion in neutral micelles (Brij-58). However, in anionic micellar medium (SDS), the probe showed selective changes with both Cu2+ and Ni2+ in the UV-vis spectroscopy. The discrimination between these two ions was achieved by emission spectroscopy, where it showed selective quenching only with Cu2+. Thus using a single probe all the three metal ions Cu2+, Hg2+ and Ni2+ can be detected and discriminated just by varying the surface charge of the micellar medium. Figure 8. Molecular structure of the sensors 15. Chapter 6. Highly sensitive Rhodamine Based Dual Probes for the Visual detection of F¯ and Hg2+ ions in Water. This chapter deals with the design and synthesis of two new rhodamine based probes (16-17) which act as dual probes for the ppb level selective detection of Hg2+ and F¯ ions in water and at physiological pH 7.4. The two probes were synthesized by coupling tert-butyldiphenylsilyl (TBDPS) protected forms of 4-hydroxybenzaldehyde and 2, 4- dihydroxy benzaldehyde with rhodamine hydrazone. The F¯ ion detection is based on the desilylation of the probe, whereas the spirolactam ring opening leads to the detection of Hg2+ ion. The two probes gave turn-on detection of both Hg2+ and F¯ ion selectively in aqueous medium with the detection limit well below the EPA permitted limits. The probes showed detection of both the ions by dual mode with visibly different color and fluorescence under UV-lamp. The F¯ ion interacts with the silyl bond of probe and the cleavage results into yellow color whereas; the addition of Hg2+ ion to the probe solution opened the spirolactam ring and resulted into appearance of pink color. Figure 9. Molecular structure of the probes 16 and 17. (For structural formula pl see the abstract file)