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1
Davies, Gillian Mary. "Degradation of cyanide and metal cyanides using fungi." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393787.
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Parab, Preeti. "Requirements for Cell-Free Cyanide Oxidation by Pseudomonas Fluorescens NCIMB 11764." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2614/.
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The involvement of cyanide oxygenase in the metabolism of pyruvate and a-ketoglutarate-cyanohydrin was investigated and shown to occur indirectly by the consumption of free cyanide arising from the cyanohydrins via chemical dissociation. Thus, free cyanide remains the substrate, for which the enzyme displays a remarkably high affinity (Kmapp,4 mM). A model for cyanide utilization is therefore envisioned in which the substrate is initially detoxified by complexation to an appropriate ligand followed by enzymatic oxidation of cyanide arising at sublethal levels via chemical dissociation. Putative cyanide oxygenase in cell extracts consumed both oxygen and NADH in equimolar proportions during cyanide conversion to CO2 and NH3 and existed separately from an unknown heat-stable species responsible for the nonenzymatic cyanide-catalyzed consumption of oxygen. Evidence of cyanide inhibition and nonlinear kinetics between enzyme activity and protein concentration point to a complex mechanism of enzymatic substrate conversion.
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Fernandez, Ruby. "Cyanide Assimilation in Pseudomonas Fluorescens: Characterization of Cyanide Oxygenase as a Pterin-Dependent Multicomponent Enzyme Complex." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc5548/.
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Cyanide utilization in Pseudomonas fluorescens NCIMB 11764 occurs via oxidative conversion to carbon dioxide and ammonia, the latter satisfying the nitrogen requirement. Substrate attack is initiated by an enzyme referred to as cyanide oxygenase (CNO), previously shown to require components in both high (H) (>30 kDa) and low (L) (<10 kDa) molecular weight cell fractions. In this study, tetrahydrobiopterin (H4biopterin) was identified as a cofactor in fraction L, thus making CNO appear as a pterin- dependent hydroxylase. CNO was purified 150-fold (specific activity 0.9 U/mg) and quantitatively converted cyanide to formate and ammonia as reaction products. When coupled with formate dehydrogenase, the complete enzymatic system for cyanide oxidation to carbon dioxide and ammonia was reconstituted. CNO was found to be an aggregate of known enzymes that included NADH oxidase (Nox), NADH peroxidase (Npx), cyanide dihydratase (CynD) and carbonic anhydrase (CA). A complex multi-step reaction mechanism is proposed in which Nox generates hydrogen peroxide which in turn is utilized by Npx to catalyze the oxygenation of cyanide to formamide accompanied by the consumption of one and two molar equivalents of oxygen and NADH, respectively. The further hydrolysis of formamide to ammonia and formate is thought to be mediated by CynD. The role of H4biopterin and of the enzyme CA in the proposed process remains unclear, but the involvement of each in reactive oxygen and radical chemistry is consistent with the proposed formation of such species in the catalytic process. H4biopterin may additionally serve as a protein stabilizing agent along with a protein co-purifying with CynD identified as elongation factor Tu, a known chaperone. At least two of the CNO components (Nox and CynD) are complex oligomeric proteins whose apparent association with Npx and CA appears to be favored in bacterial cells induced with cyanide allowing their purification in toto as a multiprotein enzyme complex.
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Leahy, Christopher David. "The oxidation by peroxides of cyanides, cyanide complexes and related species." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46407.
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Zlosnik, James Edward Arthur. "Cyanide and the cyanide insensitive oxidase in Pseudomonas aeruginosa." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421885.
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Chou, Chia-Ni. "Purification of Cyanide-Degrading Nitrilase from Pseudomonas Fluorescens NCIMB 11764." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc33224/.
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Cyanide is a well known toxicant that arises in the environment from both biological and industrial sources. Bacteria have evolved novel coping mechanisms for cyanide and function as principal agents in the biosphere for cyanide recycling. Some bacteria exhibit the unusual ability of growing on cyanide as the sole nitrogen source. One such organism is Pseudomonas fluorescens NCIMB 11764 (Pf11764) which employs a novel oxidative mechanism for detoxifying and assimilating cyanide. A unique complex of enzymes referred to as cyanide oxygenase (CNO) is responsible for this ability converting cyanide to ammonia which is then assimilated. Because one component of the four member CNO complex was previously shown to act on cyanide independent of the other members, its characterization was sought as a means of gaining a better understanding of the overall catalytic mechanism of the complex. Preliminary studies suggested that the enzyme belonged to a subset of nitrilase enzymes known as cyanide dihydratases (CynD), however, a cynD-like gene in Pf11764 could not be detected by PCR. Instead, a separate nitrilase (Nit) linked to cyanide metabolism was detected. The corresponding nit gene was shown to be one of a conserved set of nit genes traced to a unique cluster in bacteria known as Nit1C. To determine whether the previously described CynD enzyme was instead Nit, efforts were undertaken to isolate the enzyme. This was pursued by cloning and expressing the recombinant enzyme and by attempting to isolate the native enzyme. This thesis is concerned with the latter activity and describes the purification of a Nit-like cyanide-degrading nitrilase (NitCC) from Pf11764 to ~95% homogeneity. Purification was greatly facilitated by the discovery that fumaronitrile, as opposed to cyanide, was the preferred substrate for the enzyme (20 versus 1 U/mg protein, respectively). While cyanide was less effective as a substrate, the specificity for cyanide far outweighed that (10,000 fold) of the recombinant enzyme (NitPG) implying that the native NitCC protein purified in this work is different from that of the cloned recombinant. Further evidence of this was provided by molecular studies indicating that the two proteins differ in mass (34.5 and 38 kDa, respectively) and amino acid sequence. In summary, two different Nit enzymes are encoded by Pf11764. While the two share greater than 50% amino acid sequence identity, the results suggest that the native NitCC enzyme purified in this work functions better as a cyanide-degrading nitrilase and is one of four enzyme components comprising CNO required for Pf11764 cyanide assimilation.
7
Dorr, Patrick Karl. "Cyanide oxygenase and cyanase activities of Pseudomonas fluorescens NCIMB 11764." Thesis, University of Kent, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292714.
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Silva, Avalos Juan G. (Juan Guillermo). "Isolation, Characterization and Physiological Studies of Cyanide-Utilizing Bacteria." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc278291/.
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Ten bacteria capable of growth on the metal-cyano complex, tetracyanonickelate (II) {K2 [Ni(CN)J } (TCN), supplied as the sole nitrogen source, were isolated. Seven isolates were identified as pseudomonads while the remaining three were classified as Klebsiella species. In addition to TCN, all isolates were able to utilize KCN although it was significantly more toxic. The degradation of TCN was most complete when supplied at growth-limiting concentrations, did not occur when ammonia was present, and resulted in the formation of nickel cyanide [Ni(CN)2] as a degradation product.
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Nagappan, Olagappan. "Mechanisms of Cyanide Assimilation in Pseudomonas fluorescens NCIMB 11764." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc278533/.
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Pseudomonas fluorescens NCIMB 11764 was capable of utilizing cyanide as a sole nitrogen source for growth. Cyanate (OCN") and S-cyanoalanine could also serve as nitrogenous substrates, but do not appear to play a role as intermediates in cyanide metabolism. Growth of this strain on cyanate as the sole nitrogen source led to the induction of an enzyme characterized as a cyanase (EC 3.5.5.3) based on its stoichiometric conversion of cyanate to ammonia, and dependence on bicarbonate for maximal activity. However, since cyanase activity was not elevated in cyanide-grown cells it was concluded that it serves no role in cyanide metabolism. Related studies aimed at examining a possible role for S-cyanoalanine as a cyanide-assimilation intermediate showed that while this compound also serves as a nitrogen source, it also is not important in cyanide metabolism. Studies focused on the utilization of free cyanide as a growth substrate led to the development of a fed-batch cultivation procedure greatly facilitating further experimentation aimed at the identification of cyanide metabolites. In addition to CO_2 and NH_3 as described earlier, two additional metabolites including formamide and formate were detected by using nC-NMR, HPLC, radioisotrapping methods and other analytical means. The formation of metabolites was shown to be induced after growth on cyanide with the relative product yields dependent on the availability of oxygen. These findings support earlier work in which an oxygen-dependent mechanism was proposed for the formation of C02 and NH3. However, at least two additional oxygen-independent pathways of cyanide conversion can be elaborated by this organism. One of these involves conversion to formate and ammonia while the other leads to the formation of formamide, which is not further degraded. Thus, growth on cyanide appears to occur by several mechanisms of chemical transformation presumably serving both detoxification and nutritional roles. Since two of these mechanisms generate ammonia, which is readily assimilated, growth is presumed to proceed via ammonia as a provisionary nitrogenous substrate.
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Chen, Jui-Lin. "Biochemical Identification of Molecular Components Required for Cyanide Assimilation in Pseudomonas fluorescens NCIMB 11764." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278624/.
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Utilization of cyanide as a nutritional nitrogen source in P. fluorescens NCIMB 11764 was shown to involve a novel metabolic mechanism involving nonenzymatic neutralization outside of cells prior to further enzymatic oxidation within. Several cyanide degrading enzymes were produced by NCIMB 11764 in response to growth or exposure to cyanide, but only one of these cyanide, oxygenase (CNO), was shown to be physiologically required for assimilation of cyanide as a growth substrate.
11
Xie, Feng. "Solvent extraction of copper and cyanide from waste cyanide solution." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/25746.
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The potential use of two commercial extractants, LIX 7950, a guanidine derivative, and LIX 7820, a solvent mixture of quaternary amine and nonylphenol, for recovery of copper and cyanide from waste cyanide solution has been investigated. Low equilibrium pH favors copper extraction while a high molar ratio of cyanide to copper depresses the copper loading. It is confirmed that Cu(CN)²⁻₃ is preferentially extracted over Cu(CN) ³⁻₄ and CN- by the extractants.
Solvent extraction of the mixture of metal cyano complexes shows a selectivity order as follows: Zn > Ni > Cu > Fe. The presence of SO²⁻₄ or S₂O²⁻₃ shows an insignificant effect on copper extraction while SCN- ions may potentially compete for the available extractant with copper cyanide species and thus depress copper extraction significantly. Both extractants exhibit an affinity sequence as SCN- > CNO- > CN-> S₂O²⁻₃. The selectivity order of different anions with the extractants can be explained by the interrelated factors including anion hydration, charge density, compatibility of the formed complex with the organic phase and the geometry effect.
The extraction of Cu(CN)²⁻₃ with LIX 7950 is exothermic with an enthalpy change (ΔH°) of -191 kJ/mol. The copper extraction with LIX 7820 has little change when the temperature is varied from 25 °C to 45 °C. For both extractants, the loaded copper and cyanide can be stripped efficiently by a moderately strong NaOH solution. Further increase in NaOH concentration results in the formation of a third phase. The presence of NaCN can facilitate stripping of the loaded copper and cyanide by favoring the formation of Cu(CN)³⁻₄ in the stripping solution.
The important findings suggest a possible solution to the separation of metal cyanide species and free cyanide in the cyanide effluent. Both extractants can be used in a SX circuit for pre-concentrating copper into a small volume of strip solution which can be further treated by
electrowinning, AVR, SART or similar processes to recover copper products and cyanide. The free cyanide will remain in the raffinate solution from solvent extraction circuit which allows for the potential recycling of the barren solution to the gold cyanidation process.
12
Wang, Chien-Sao. "Cell-Free Recovery and Isotopic Identification of Cyanide Degrading Enzymes from Pseudomonas Fluorescens." Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc278363/.
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Cell-free extracts from Pseudomonas fluorescens NCIMB 11764 catalyzed the degradation of cyanide into products that included C02, formic acid, formamide and ammonia. Cyanide-degrading activity was localized to cytosolic cell fractions and was observed at substrate concentrations as high as 100 mM. Two cyanide degrading activities were identified by: (i) the determination of reaction products stoichiometries, (ii) requirements for NADH and oxygen, and (iii) kinetic analysis. The first activity produced CO2 and NH3 as reaction products, was dependent on oxygen and NADH for activity, and displayed an apparent Km for cyanide of 1.2 mM. The second activity generated formic acid (and NH3) pfus formamide as reaction products, was oxygen independent, and had an apparent Km of 12 mM for cyanide. The first enzymatic activity was identified as cyanide oxygenase whereas the second activity consists of two enzymes, a cyanide nitrilase (dihydratase) and putative cyanide hydratase. In addition to these enzymes, cyanide-grown cells were also induced for formate dehydrogenase (FDH), providing a means of recycling NADH utilized by cyanide oxygenase.
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Dolghih, Elena. "Bacterial Cyanide Assimilation: Pterin Cofactor and Enzymatic Requirements for Substrate Oxidation." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4525/.
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Utilization of cyanide as the sole nitrogen source by Pseudomonas fluorescens NCIMB 11764 (Pf11764) occurs via oxidative conversion to carbon dioxide and ammonia, the latter satisfying the nitrogen requirement. Substrate attack is initiated oxygenolytically by an enzyme referred to as cyanide oxygenase (CNO), which exhibits properties of a pterin-dependent hydroxylase. The pterin requirement for Pf11764 CNO was satisfied by supplying either the fully (tetrahydro) or partially (dihydro) reduced forms of various pterin compounds at catalytic concentrations (0.5 µM). These compounds included, for example, biopterin, monapterin and neopterin, all of which were also identified in cell extracts. A related CNO-mediated mechanism of cyanide utilization was identified in cyanide-degrading P. putida BCN3. This conclusion was based on (i) the recovery of CO2 and NH3 as enzymatic reaction products, (ii) the dependency of substrate conversion on both O2 and NADH, and (iiii) utilization of cyanide, O2 and NADH in a 1:1:1 reaction stoichiometry. In contrast to findings reported for Pf11764, it was not possible to demonstrate a need for exogenously added pterin as a cofactor for the PpBCN3 enzyme system. However, results which showed that cells of PpBCN3 contained approximately seven times the amount of pterin as Pf11764 (of which a significant portion was protein-bound) were interpreted as indicating that sufficient bound CNO-cofactor exists, thus eliminating any need for a supplemental source.
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Akinpelu, Enoch Akinbiyi. "Thermodynamic study of the biodegradation of cyanide in wastewater." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2554.
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Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.The high rate of industrialisation in most developing countries has brought about challenges of wastewater management especially in the mineral processing industry. Cyanide has been used in base metal extraction processes due to its lixiviant properties thus, its presence in wastewater generated is inevitable. Furthermore, partial and/or the use of unsuitable treatment methods for such wastewater is a potential hazard to both human and the environment. There are several reports on biotechnological treatments of cyanide containing wastewater but few mineral processing industries have adopted this approach. Hence, the thermodynamic study of biodegradation of cyanide containing wastewater was undertaken. The primary aim of this study was to explore the application of bioenergetic models and biological stoichiometry to determine the functionality and thermodynamic requirements for cyanide degrading isolate (Fusarium oxysporum EKT01/02), grown exclusively on Beta vulgaris, for a system designed for the bioremediation of cyanidation wastewater. Chapter 2 reviews some of the applicable thermodynamic parameters such as enthalpy, entropy, heat of combustion, heat capacity, Gibbs energy, including stoichiometry models in relation to their applicability for microbial proliferation in cyanidation wastewater. The chapter places emphasis on the application of agro-industrial waste as a suitable replacement for refined carbon sources for microbial proliferation in bioremediation systems because such systems are environmentally benign. The choice of using agro-industrial waste is due to organic waste properties, i.e. agro-industrial waste is rich in nutrients and is generated in large quantities. Chapter 3 presents the materials and various standardised methods used to address the research gaps identified in chapter 2. For an organism to degrade free cyanide in wastewater, it must be able to survive and perform its primary function in the presence of such a toxicant. Chapter 4 exemplifies both molecular and biochemical characteristics of Fusarium oxysporum EKT01/02 isolated from the rhizosphere of Zea mays contaminated with a cyanide based pesticide. The molecular analyses confirmed the fungal isolate to be Fusarium oxysporum EKT01/02 and the nucleotide sequence of the isolates were deposited with National Centre for Biotechnology Information (NCBI) with accession numbers KU985430 and KU985431. The biochemical analyses revealed a wide substrate utilisation mechanism of the isolate dominated by aminopeptidase including nitrate assimilation capabilities. A preliminary investigation showed free cyanide degradation efficiency of 77.6% (100 mg CN-/L) after 5 days by the isolate. The excess production of extracellular polymeric substance (EPS) was attributed to the isolates’ strive to protect itself from cyanide toxicity.
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Mekuto, Lukhanyo. "Biodegradation of cyanide and subsequent nitrification-aerobic denitrification in cyanide containing watewater." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/868.
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Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Chemical Engineering
in the Faculty of
Engineering
at the
Cape Peninsula University of Technology
2014Environmental legislation focusing on wastewater disposal in industries that utilise cyanide and/or cyanide-related compounds has become increasingly stringent worldwide, with many companies that utilise cyanide products required to abide by the Cyanide International Code associated with the approval of process certifications and management of industries which utilise cyanide. This code enforces the treatment or recycling of cyanide-contaminated wastewater. Industries such as those involved in mineral processing, photo finishing, metal plating, coal processing, synthetic fibre production, and extraction of precious metals, that is, gold and silver, contribute significantly to cyanide contamination in the environment through wastewater. As fresh water reserves throughout the world are low, cyanide contamination in water reserves threatens not only the economy, but also endangers the lives of living organisms that feed from these sources, including humans. In the mining industry, dilute cyanide solutions are utilised for the recovery of base (e.g. Cu, Zn, Ni, etc.) and precious metals (e.g. Au, Ag, etc.). However, for technical reasons, the water utilised for these processes cannot be recycled upstream of the mineral bioleaching circuit as the microorganisms employed in mineral bioleaching are sensitive to cyanide and its complexes, and thus the presence of such compounds would inhibit microbial activity, resulting in poor mineral oxidation. The inability to recycle the water has negative implications for water conservation and re-use, especially in arid regions. A number of treatment methods have been developed to remediate cyanide containing wastewaters. However, these chemical and physical methods are capital intensive and produce excess sludge which requires additional treatment. Furthermore, the by-products that are produced through these methods are hazardous. Therefore, there is a need for the development of alternative methods that are robust and economically viable for the bioremediation of cyanide-contaminated wastewater. Biological treatment of free cyanide in industrial wastewaters has been proved a viable and robust method for treatment of wastewaters containing cyanide. Several bacterial species, including Bacillus sp., can degrade cyanide to less toxic products, as these microorganisms are able to use the cyanide as a nitrogen source, producing ammonia and carbon dioxide. These bacterial species secrete enzymes that catalyse the degradation of cyanide into several end-products. The end-products of biodegradation can then be utilised by the microorganisms as nutrient sources. This study focused on the isolation and identification of bacterial species in wastewater containing elevated concentrations of cyanide, and the assessment of the cyanide biodegradation ability of the isolates. Thirteen bacterial isolates were isolated from electroplating wastewater by suppressing the growth of fungal organisms and these species were identified as species belonging to the Bacillus genus using the 16S rDNA gene. A mixed culture of the isolates was cultured in nutrient broth for 48 hours at 37°C, to which FCN as KCN was added to evaluate the species‟ ability to tolerate and biodegrade cyanide in batch bioreactors. Subsequently, cultures were supplemented solely with agro-waste extracts, that is, Ananas comosus extract (1% v/v), Beta vulgaris extract (1% v/v), Ipomea batatas extract (1% v/v), spent brewer‟s yeast (1% v/v) and whey (0.5% w/v), as the primary carbon sources. Owing to the formation of high ammonium concentration from the cyanide biodegradation process, the nitrification and aerobic denitrification ability of the isolates, classified as cyanide-degrading bacteria (CDB) was evaluated in a batch and pneumatic bioreactor in comparison with ammonia-oxidising bacteria (AOB). Furthermore, the effects of F-CN on the nitrification and aerobic denitrification was evaluated assess the impact of F-CN presence on nitrification. Additionally, optimisation of culture conditions with reference to temperature, pH and substrate concentration was evaluated using response surface methodology. Using the optimised data, a continuous biodegradation process was carried out in a dual-stage packed- bed reactor combined with a pneumatic bioreactor for the biodegradation of F-CN and subsequent nitrification and aerobic denitrification of the formed ammonium and nitrates. The isolated bacterial species were found to be gram positive and were able to produce endospores that were centrally located; using the 16S rDNA gene, the species were found to belong to the Bacillus genus. The species were able to degrade high cyanide concentration in nutrient broth with degradation efficiencies of 87.6%, 65.4%, 57.0% and 43.6% from 100 mg F-CN/L, 200 mg F-CN/L, 300 mg F-CN/L, 400 mg F-CN/L and 500 mg F-CN/L respectively over a period of 8 days. Additionally, the isolates were able to degrade cyanide in an agro-waste supported medium, especially in a medium that was supplemented with whey which achieved a degradation efficiency of 90% and 60% from 200 mg F-CN/L and 400 mg F-CN/L, respectively over a period of 5 days. The nitrification ability of the isolates was evaluated and the removal of NH4 +/NO3 - by the CDB and AOB in both shake flasks and pneumatic bioreactor was determined to be pH dependent. The maximum NH4 +/NO3 - removal evaluated over a period of 8 days for CDB and 15 days for AOB, observed at pH 7.7 in shake flasks, was 75% and 88%, respectively, in the absence of F-CN. Similarly, the removal of NH4 +/NO3 - in a pneumatic bioreactor was found to be 97.31% for CDB and 92% for AOB, thus demonstrating the importance of aeration in the designed process. The nitrification by CDB was not inhibited by cyanide loading up to a concentration of 8 mg FCN/ L, while the AOB were inhibited at cyanide loading concentration of 1 mg F-CN/L. The CDB removed the NH4 +/NO3 - in PBSs operated in a fed-batch mode, obtaining efficiencies >99% (NH4 +) and 76 to 98% (NO3 -) in repeated cycles (n = 3) under F-CN (≤8 mg F-CN/L). The input variables, that is, pH, temperature and whey-waste concentration, were optimised using a numerical optimisation technique where the optimum conditions were found to be: pH 9.88, temperature 33.60 °C and whey-waste concentration 14.27 g/L, under which 206.53 mg CN-/L in 96 h can be biodegraded by the microbial species from an initial cyanide concentration of 500 mg F-CN/L. Furthermore, using the optimised data, cyanide biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor connected in series to a pneumatic bioreactor system used for simultaneous nitrification including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by the free cyanide concentration of up to 500 mg F-CN/L, with an overall degradation efficiency of ≥99% with subsequent nitrification and aerobic denitrification of the formed ammoniu and nitrates over a period of 80 days.
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Pan, Guangliang. "Role of α-Keto Acids In Cyanide Detoxification and Assimilation by Pseudomonas Bacteria." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc500761/.
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Cyanide was rapidly removed when added to culture supernatants of seven different Pseudomonas. The ability to remove cyanide was correlated with the accumulation of α-keto acids (pyruvate and α-ketoglutarate). These compounds react with cyanide forming less toxic cyanohydrins, thus conferring a mechanism for bacterial cyanide tolerance. When added to growth media the α-keto acids were shown also to serve as effective cyanide antagonists. While all bacteria tested accumulated α-keto acids, only those capable of utilizing cyanide as a nutritional nitrogen source were able to metabolize cyanohydrins. In P. fluorescens NCIMB 11764, the same enzyme (cyanide oxygenase) shown previously to be involved in cyanide metabolism appears responsible for cyanohydrin transformation. Keto acid excretion is believed to represent a new mechanism of bacterial cyanide detoxification with further enzymatic metabolism of the cyanohydrins helping to explain how cyanide can satisfy the nitrogen requirement in cyanide-utilizing bacteria.
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Larsen, Morten. "Plant uptake of cyanide." Kgs. Lyngby : Institute of Environment & Resources, Technical University of Denmark, 2005. http://www.er.dtu.dk/publications/fulltext/2005/MR2005-044.pdf.
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Solis, Jose S. "Thermodynamics of cyanide complexes." Thesis, Solis, Jose S. (1995) Thermodynamics of cyanide complexes. PhD thesis, Murdoch University, 1995. https://researchrepository.murdoch.edu.au/id/eprint/52731/.
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The work described in this thesis was to study the thermodynamics of the binding of cyanide to metal ions of relevance to the hydrometallurgical processing of gold. In particular, to produce reliable and accurate thermodynamic data needed to develop reliable chemical speciation models for the gold-refining industry, especially with regard to the high saline conditions of many Australian operations.
The stability constants of binary and ternary Cu(I) systems were studied using potentiometric glass electrode titration and evaluation of results by the ESTA suite of computer programs. In particular, the study of the Cu(I)-CN- system produced four major binary species in the conditions studied. The stability constants for the three species, Cu(CN)2-, Cu(CN)32-, and Cu(CN)43- are reported. The Cu(I)-NH3 system was attempted but oxidation of Cu(I) in the presence of ammonia was observed to be fast even in the absence of air. The presence of a high Cl" concentration stabilizes Cu(I) and since it also complexes with the metal the ternary system of Cu(I)-NH3-Cl- was considered. This study has established the existence of three ternary species, Cu(NH3)Cl°, CuNH3Cl2- and Cu(NH3)2Cl° together with the binary Cu(NH3)+ in the conditions of the present study. The other ternary system, Cu(I)-NH3-CN-, was studied but no analysis could be made with the present evaluation method. Failure of these experiments may be due to the closeness of the protonation constants of cyanide and ammonia in this medium, thus making it difficult to detect the minor effects in the experimental data which may arise from the ternary complex formation. Also, the experiment is restricted from the variation of the free cyanide and ammonia concentration because of the oxidation of Cu(I), volatility of NH3 at high p[H] and the volatility of HCN at low p[H].
Measurements of heat of reactions of common metal-cyanide systems were calorimetrically determined by the isoperibol continuous titration calorimeter. Enthalpies of metal-cyanide complexation were determined from these calorimetric measurements. Included in this study was the measurement of the heat of ionization of water and HCN as they were relevant to the metal-cyanide heats of reaction studies. These two systems were studied at variable ionic strength.
The solubility of AgCN and CuCN in HCN aqueous solution was studied. Another method of deriving equilibrium constants is from solubility measurements. The apparent solubility product constant of both AgCN and CuCN were sucessfully measured using the pH variation method.
Heat capacity measurements were conducted with cyanide solution using the Picker-flow calorimeter. Measurement of the volumetric heat capacities required densities which were measured accurately using a Vibrating Tube densimeter, thus the apparent molar volumes were also reported for these cyanide solutions. From these heat capacity measurements and other relevant literature data the change in heat capacity in association to the ionization of HCN was derived. For the first time, such data were determined calorimetrically and reported. The present values were obtained from NaCN and KCN respectively, and are, -228.5 and -222.8 J K-1mo-1. The results are in very good agreement and provides a most reliable estimate of ∆Cp° for the ionization of HCN.
By establishing reliable equilibrium constants in this way, a better and accurate description of the chemistry of a given aqueous cyanide solution is achieved. These thermodynamic information obtained at high saline medium serve to develop more realistic models of such hydrometallurgical solutions in local processing industries.
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Guilfoyle, Laurence Michael. "Quartz crystal microbalance analysis for cyanide and cyanide-degrading bacteria in gold process solutions." Thesis, Guilfoyle, Laurence Michael (1998) Quartz crystal microbalance analysis for cyanide and cyanide-degrading bacteria in gold process solutions. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/52707/.
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Cyanide is used by the gold mining industry to extract gold from ore. The accurate measurement of cyanide in process solutions and the removal of cyanide from wastes are two areas of significant concern for the gold mining industry.
Biological cyanide destruction has been used successfully to remove cyanide from process solutions and leachate from heap leach pads. The aim of this work was to investigate cyanide degrading bacteria from gold mines in Western Australia.
In order to measure the activity of cyanide degrading bacteria, a method was developed to determine cyanide in small sample sizes. An apparatus and method for measuring cyanide ion in gold process solutions is described. The potential of a solution to leach gold was measured by quartz crystal microbalance, flow injection analysis. Cyanide levels from 0.5 to 500 mg L-1 were determined every two minutes on sample sizes from 0.1 to 2.5 mL. Also described is an apparatus and method for rapid measurement of weak acid dissociable (WAD) cyanide. A gas permeable membrane cell was combined with quartz crystal microbalance, flow injection analysis to measure WAD cyanide. WAD cyanide levels from 0.5 to 500 mg L-1 were determined every two minutes on sample sizes from 1.0 to 2.5 mL.
These methods were developed to measure the activity of cyanide degrading bacteria in gold process solutions. A sub species of the bacterium, Bacillus pumilus, was isolated from a gold mine in Western Australia. It degraded cyanide to ammonia and formate. The bacterium was found to exhibit high levels of cyanide degrading activity (800 units L*1) which was maintained after storage at 4°C as the bacteria did not sporulate under these conditions. This bacterium could not degrade WAD cyanide and could not grow in the presence of cyanide above 10 mg L-1.
A mixed culture of bacteria was isolated from a second gold mine that could grow in the presence of cyanide and could degrade 150 mg L-1 of WAD cyanide to below 0.5 mg L-1 in leachate from dump leached ore. Column tests showed that the addition of nutrients alone could stimulate bacteria already present in the ore to degrade cyanide. The rate of cyanide destruction in the nutrient only column was approximately half the rate of the column to which bacteria had been added. The nutrient only treatment method could reduce treatment costs for the decommissioning of heap leach pads as no bioreactor would be required.
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Jones, Lauren Brittany. "Defining Components Linked to Bacterial Nutritional Utilization of Cyanide as a Sole Nitrogen Source." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505253/.
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One of the challenges in biology is placing a function on the myriad of gene sequences having become available from rapid advances in genome sequencing. One such example is a gene cluster (Nit1C) found in bacteria that is tied to the unusual ability of certain bacteria to grow when supplied cyanide as the sole nitrogen source. The term cyanotrophs has been applied to such bacteria, for which a genetic linkage between cyanotrophy and Nit1C was demonstrated for 10 separate bacteria. In addition to growth, cyanide induced the expression of Nit1C genes in all organisms tested, and in one case, deletion of one of the Nit1C genes (nitC) caused a loss of growth. Of the ten bacteria able to grow cyanotrophically, all gave evidence of harboring Nit1C on their genome except for two (Pseudomonas fluorescens Pf11764 and P. monteilii BCN3), which were sequenced and the presence of Nit1C was also confirmed. A broader search of bacteria identified 270 separate strains with the cluster, all limited to bacteria spanning the phyla Firmicutes, Actinobacteria, Proteobacteria and Cyanobacteria. Remarkably, many examples of a single representative of a given taxon contained Nit1C, most poignantly displayed by Pf11764 and PmBCN3; the interpretation being the cluster was likely acquired by horizontal gene transfer in response to cyanide as an environmental cue. Consistent with its absence in Archaea is the time line for the emergence of cyanide producing organisms (cyanogens) on earth dating back only 400-500 million years.
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Basile, Lacy Jamel. "Cyanide-degrading enzymes for bioremediation." Texas A&M University, 2008. http://hdl.handle.net/1969.1/86035.
Full textAbstract:
Cyanide-containing waste is an increasingly prevalent problem in today's
society. There are many applications that utilize cyanide, such as gold mining and
electroplating, and these processes produce cyanide waste with varying conditions.
Remediation of this waste is necessary to prevent contamination of soils and water.
While there are a variety of processes being used, bioremediation is potentially a more
cost effective alternative.
A variety of fungal species are known to degrade cyanide through the action of
cyanide hydratases, a specialized subset of nitrilases which hydrolyze cyanide to
formamide. Here I report on previously unknown and uncharacterized nitrilases from
Neurospora crassa, Gibberella zeae, and Aspergillus nidulans. Recombinant forms of
four cyanide hydratases from N. crassa, A. nidulans, G. zeae, and Gloeocercospora
sorghi were prepared after their genes were cloned with N-terminal hexahistidine
purification tags, expressed in Escherichia coli and purified using immobilized metal
affinity chromatography. These enzymes were compared according to their relative
specific activity, pH activity profiles, thermal stability, and ability to degrade cyanide in
the presence of high concentrations of copper and silver. Although all four were relatively similar, the N. crassa cyanide hydratase (CHT)
has the greatest thermal stability and widest pH range where activity remained above
50%. N. crassa also demonstrated the highest rate of cyanide degradation in the
presence of both metals tested. The CHT of A. nidulans and N. crassa have the highest
reaction rate of the four fungal nitrilases evaluated in this work.
These data help determine optimization conditions for the possible use of these
enzymes in the bioremediation of cyanide-containing waste. Similar to known plant
pathogenic fungi, in vivo expression of CHT in both N. crassa and A. nidulans were
induced by growth in the presence of KCN (potassium cyanide).
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Ezzi, Mufaddal I. "Cyanide detoxification by soil microorganisms." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/842816/.
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Cyanides enter the environment through both natural and man-made sources. Natural sources include cyanogenesis by bacteria, fungi and plants. A number of cyanide catabolising microorganisms have also been reported in literature. This is the first reported instance of cyanide catabolism in Trichoderma harzianum. Four strains of T. harzianum, one of T. pseudokoningii were evaluated. An investigation was made into the occurrence and distribution of the cyanide catabolising enzymes. Three enzymes, cyanide hydratase, beta-cyanoalanine synthase and rhodanese, were studied. All the strains showed a high capacity to degrade cyanide via both the cyanide hydratase and rhodanese pathways, beta-cyanoalanine synthase activity, however, was not detected in any of the selected strains. In the studies on the kinetic characterization of the rhodanese enzyme, a broad pH optimum of 8.5 - 10.5 was obtained for all the strains and a broad temperature optimum of 35 - 55 °C was also observed. The KmCN and Vmax values ranged from 7-16 mM and from 0.069 - 0.093 betamoles. Min-1. mg protein-1, respectively, between the selected strains of Trichoderma. Strong evidence of cyanide biodegradation and co-metabolism emerged from studies with flask cultures where glucose was provided as a co-substrate. The rate of degradation of 2000 ppm CIST was enhanced almost three times in the presence of glucose. Plant microcosm studies carried out using pea and wheat seeds too gave further corroboration of the cyanide degrading and plant growth promotion capabilities of Trichoderma. Microcosms set-up with cyanide at 50 or 100 ppm CN, in the presence of Trichoderma, showed germination of both pea and wheat seeds. There was no seed germination in any of the controls in the absence of Trichoderma inoculation.
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Lu, Jianming. "Copper electrowinning from cyanide solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/NQ48655.pdf.
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Convine, Nicola Jane. "Stereoselective conjugate addition of cyanide." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424510.
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Molojwane, Emang Tsametse Emi. "Engineering cyanide-tolerant Arabidopsis thaliana." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19996.
Full textAbstract:
Cyanide is highly toxic as it inhibits respiration in aerobic organisms by binding to cytochrome c oxidase in the mitochondrial electron transport chain. Plants naturally produce cyanide from the hydrolysis of cyanogenic glycosides and as a by-product of ethylene biosynthesis. β-Cyanoalanine synthase prevents self-poisoning by combining endogenous cyanide with cysteine in the mitochondria to form β-cyanoalanine, which is further hydrolysed to asparagine, or aspartate and ammonia, by plant nitrilase 4 enzymes. β-Cyanoalanine synthase activity enables plants to detoxify limited concentrations of exogenous cyanide. However, phytotoxicity and death occur from exposure to relatively low concentrations of exogenous cyanide. In contrast, some microorganisms have a high capacity for cyanide detoxification due to a number of metabolic pathways including the degradation of cyanide to formate and ammonia; or formamide, by bacterial cyanidase (CynD) and fungal cyanide hydratase (CHT), respectively. Environmental contamination caused by failure to contain cyanide from anthropogenic sources is an important global problem. Hydrometallurgical gold mining utilises cyanide as a lixiviant due to the high affinity of cyanide for gold and the stability of the resulting cyanometallic complexes in aqueous solution, and thus is a significant source of cyanide contamination of soil and water. Biological treatment methods for cyanide, such as phytoremediation, could provide alternatives to the currently used chemical destruction techniques with their associated disadvantages. The use of phytoremediation would require plants to tolerate high concentrations of cyanide in soil. Two attempts have previously been made, with some success, to increase cyanide tolerance in Arabidopsis by genetic engineering: the first, by augmenting the β-cyanoalanine synthase pathway using a microbial nitrilase; and, the second, by introducing a microbial detoxification pathway targeted to the chloroplasts while overexpressing the endogenous enzyme which metabolises the product of the cyanide detoxification reaction. The aim of the current study was to determine whether Arabidopsis thaliana could co-opt the CynD and CHT genes from the cyanide-degrading Bacillus pumilus and Neurospora crassa to detoxify higher levels of cyanide using the encoded enzymes, and whether targeting CynD and CHT to the mitochondria would confer a greater enhancement of cyanide tolerance on plants compared to targeting to the cytoplasm.
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Sidibe, Aissatou. "EFFECT OF ABIOTIC STRESSES AND CYANIDE TREATMENT ON THE CYANIDE ASSIMILATORY PATHWAY IN ARABIDOPSIS THALIANA." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1674095021&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Ghosh, Pallab. "Linkage of a nitrilase-containing Nit1C gene cluster to cyanide utilization in Pseudomonas fluorescens NCIMB 11764." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc10993/.
Full textAbstract:
Pseudomonas fluorescens NCIMB 11764 (Pf11764) is uniquely able to grow on the poison cyanide as its sole nitrogen source. It does so by converting cyanide oxidatively to carbon dioxide and ammonia, the latter being assimilated into cellular molecules. This requires a complex enzymatic machinery that includes nitrilase and oxygenase enzymes the nature of which are not well understood. In the course of a proteomics analysis aimed at achieving a better understanding of the proteins that may be required for cyanide degradation by Pf11764, an unknown protein of 17.8 kDa was detected in cells exposed to cyanide. Analysis of this protein by ESI-coupled mass spectrometry and bioinformatics searches gave evidence of strong homology with a protein (Hyp1) of unknown function (hypothetical) present in the bacterium Photorhabdus luminescens subsp. laumondii TTO1 (locus plu_1232). A search of available microbial genomes revealed a number of Hyp1 orthologs the genes of which are found in a conserved gene cluster known as Nit1C. Independent studies revealed that in addition to Hyp1, Pf11764 possesses a gene (nit) specifying a nitrilase enzyme whose closest homologue is a nitrilase found in Nit1C gene clusters (77% amino acid identity). DNA sequence analysis has further revealed that indeed, hyp1Pf11764 and nitPf11764 are contained in a cluster that includes also a gene specifying an oxygenase. Given the possible connection of Nit1C-endoded nitrilase and oxygenase enzymes to enzymatic cyanide degradation, there is strong reason for thinking that the genes specifying these enzymes contribute to bacterial growth on cyanide in those bacteria containing the Nit1C cluster. Because the biological function of the Hyp1 protein is currently unknown, it was cloned and the protein expressed in E. coli so that its properties could further be explored. Unfortunately, the expression of the protein in an insoluble form complicated these analyses. However, at least two lines of evidence suggest a possible role as a regulator of gene expression. First, over-expression of the protein was accompanied by the parallel elevation of the putative vector-encoded b-lactamase, implying that Hyp1Pf11764 can affect the expression of other genes. Second, a comparison of the amino acid sequence of select peptide fragments of Hyp1Pf11764, by conducting searches for homology with proteins in the existing nonredundant protein database, consistently revealed motifs in common with those present in bacterial response regulators that are part of two-component signal transduction systems widely distributed in bacteria.
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Llamas-Rey, Estefania. "Redox-active cyanide-bridged dimanganese complexes." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390645.
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Onganusorn, Sriwipha. "Cyanide complexes as redox-active ligands." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425135.
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Rehbein, Marcus. "Polymere Metallcyanide als Vorstufen für intermetallische Phasen und Mischoxide." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96310487X.
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Perera, Weeratunge Nimal. "Hydrolysis and cyanide speciation of some heavy metals relevant to the fate of cyanide in the environment." Thesis, Perera, Weeratunge Nimal (2001) Hydrolysis and cyanide speciation of some heavy metals relevant to the fate of cyanide in the environment. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/5300/.
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Quantitative understanding of the fate of cyanide in the environment and its role in industrial processes requires quantitative characterisation of metal ion–cyanide complex formation and also the corresponding metal ion hydrolysis reactions that frequently compete with them. This thesis presents quantitative data for complex formation constants obtained using a range of techniques for a number of metal ion–hydroxide and metal ion–cyanide systems of environmental and hydrometallurgical importance that have been found difficult to study in the past. A specially–constructed combined spectrophotometric /potentiometric cell has enabled a variety of systems to be studied by UV–Visible spectroscopy at very low metal ion concentrations. This has circumvented problems associated with precipitation and/or polynuclear metal complex formation, which frequently predominate in these systems at higher concentrations.
Using this approach it has been possible to determine the formation constants and spectra of the mononuclear hydroxide complexes of Pb(II), Cu(II), Fe(III), Ag(I) and for the cyanide complexes of Pb(II), Ag(I), Ni(II) and Fe(III). It has also been possible to estimate the solubility products of Pb(CN)2(s), AgOH(s), AgCN(s) and NaFeFe(CN)6(s). For some of these species (namely, Pb(OH)42–, the higher order hydroxo–complexes of Cu(II) and Fe(III), Pb(CN)+, and the lower cyano–complexes of Fe(III)), the present results are the first quantitative estimates of their formation constants. These complexes have long been assumed to exist on theoretical grounds but have proven difficult to quantify experimentally. The main reasons for this difficulty are the sparing solubility of the neutral hydroxides and /or cyanides and the tendency of CN– to form either very weak or extremely strong complexes.
Where possible, attempts were made to confirm the spectrophotometric results using other techniques such as polarography, NMR spectroscopy (for Pb(II)), Raman spectroscopy and, for Cu(II), ESR spectroscopy. However, although these techniques were sometimes able to provide useful insights into the nature of the species formed, in general they were not sufficiently sensitive, or suffered from other constraints that meant that they yielded little quantitative information.
The formation constants measured in this work were combined with literature data to model the chemical behaviour of hypothetical cyanide–infiltrated soil. This modelling indicates that under typical contaminated soil conditions (i.e. soil containing Fe(OH)3(s) and [CN–] = 0.1mM), cyanide will be present mainly as the various forms of Prussian blue. However, strong competition between cyanide and hydroxide ions for Fe(III), points to possible conditions for the chemical degradation of the Prussian blue.
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Sevim, Ilhan. "Reactions Of Diethylaluminum Cyanide With Acyl Phosphonates." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611557/index.pdf.
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This thesis includes reaction of diethylaluminum cyanide with acyl phosphonates. Cyanohidrin O-phosphates are synthesized from easily available acyl phosphonates and diethylaluminum cyanide. Synthesis of cross-benzoin product of acyl phosphonate, α
-hydroxy phosphonate and tertiary carbinol are synthesized from the reaction of diethylaluminum cyanide with acyl phosphonates, representatively. Asymmetric syntheses of cyanohydrin and benzoin type reaction of acyl phoshonate are also investigated representatively.
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Onabolu, Adeyinka. "Cassava processing, consumption and dietary cyanide exposure /." Stockholm, 2001. http://diss.kib.ki.se/2001/91-628-4894-1/.
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Rozario, Hoimonti Immaculata. "Spectroscopic study of acetylene and hydrogen cyanide." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2012, 2012. http://hdl.handle.net/10133/3415.
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High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213–333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters.
The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results.
We have studied the line intensities of the 1νl20←0νl20 band system from the HCN emission spectrum. The infrared emission spectrum of H12C14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.viii, 112 leaves : ill. ; 29 cm
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Hope, Karen Mary. "Cyanide and nitrile transformations in anaerobic cultures." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302993.
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Vaz, Marcela Carraro de Melo. "Thiocyanate excretion can reveal cyanide caught fish." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/8326.
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Mestrado em Biologia MarinhaA pesca com cianeto (CN-) e uma técnica destrutiva utilizada na colheita de peixes vivos de recifes de coral. Estes organismos apresentam elevado valor económico e são destinados tanto para o consumo humano como para o abastecimento da indústria mundial de aquários marinhos. Diversas são as tecnicas capazes de detectar a presenca do cianeto (CN-) em peixes, contudo ainda não há um consenso entre a comunidade científica e os comerciantes sobre qual destas técnicas será a mais eficaz, uma vez que as mais utilizadas ainda são de caráter invasivo. Neste trabalho foi utilizada uma técnica não invasiva e não destrutiva, e mais eficiente, no que diz respeito ao tempo de análise, onde através do uso da fibra óptica (FO) podem ser detectados peixes contaminados com cianeto num tempo médio < 6 min. por meio da excrecão de tiocianato (SCN-). Produto de excreção do (CN-), esse metabolito permite a desintoxicação dos peixes marinhos expostos ao contaminante pelas vias urinárias e os níveis anormais de SCN- presentes na agua marinha indicarão se os exemplares foram ou não expostos ao envenenamento por CN-. A metodologia (FO) foi capaz de detectar níveis ainda que residuais de SCN(> 3; 16mgL - 1) na agua marinha e os níveis base para os organismos não contaminados foram utilizados como referência para classi ficação de presença ou ausência de contaminação. Nesse estudo exemplares de Amphiprion clarkii cultivados em cativeiro foram expostos a um pulso de solução de CN- durante 60 s para as concentrações de 12,5e25, 0mgL - 1 e os resultados obtidos para o CN- excretado, pós-exposição ao longo de 28 dias, foram de até 6,96 ± 0,03 e 9,84 ± 0,03mgL - 1 de SCN- (respectivamente). Apesar da necessidade de mais investigação para diminuir a ocorrência de falsos negativos e positivos, a metodologia testada permite uma rápida detecção do SCN- sem o sacrifício dos espécimes analisados.
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Mpongwana, Ncumisa. "Nitrification and aerobic denitrification in cyanide-containing wastewater." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2371.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.Anthropogenic activities that utilise cyanide in various chemical forms have resulted in the disposal of cyanide-contaminated effluents into drainage systems that ultimately reach wastewater treatment plants (WWTP), without prior treatment. Cyanides (CN) and soluble salts could potentially inhibit biological processes in WWTP, which are responsible for the removal of contaminants from incoming wastewaters. The removal of nitrogenous compounds from such waters in processes such as nitrification and denitrification is among the core biological processes used to treat wastewaters in WWTP. Electroplating and mining industries are among the perpetrators of cyanide contamination of WWTP. The presence of these hazardous contaminants results in the alteration of metabolic functions of the microbial populations that are utilised in WWTP, thus rendering the wastewater treatment process ineffective. In this study, bacterial isolates that were able to carry out nitrification and aerobic denitrification under high salinity cyanogenic conditions were isolated from poultry slaughterhouse effluent. These strains were referred to as I, H and G. The isolated bacterial species were found to be able to oxidise ammonium nitrogen (NH4-N) in the presence of free cyanide (CN-) under halophilic conditions. Isolates I, H and G were identified using the 16S rDNA gene and were identified to be Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Furthermore, Response Surface Methodology was used to optimise the physicochemical conditions suitable for the proliferation of the isolates for free-cyanide degradation, nitrification and aerobic denitrification.
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Garnier, Delphine. "Open-shell Coordination Compounds based on Cyanide and Scorpionate Ligands." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066296/document.
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Cette thèse porte sur la synthèse et la caractérisation de complexes octaédrique de fer(II) et fer(III) coordinés par un ligand tridente de type scorpionate (symétrie fac) et par trois ligands cyanures. Leur utilisation en tant que metalloligand face à des ions métalliques partiellement bloqués est étudiée. Les ligands cyanures, de par leur caractère ambidente, permettent un accès facile aux espèces hétérobimétalliques. De plus, ces ligands sont connus pour transmettre efficacement l'interaction d'échange magnétique et donc pour favoriser la communication électronique intramoléculaire entre les ions métalliques qu'ils relient. La fonctionalisation des ligands scorpionates permet de contrôler les propriétés électroniques intrinsèques des complexes précurseurs de fer, et donc de moduler les propriétés des espèces polynucléaires obtenues à partir de ces dernières par auto-assemblage. Dans cette thèse, un intérêt particulier est porté aux systèmes {FeCo} en raison de leur capacité à présenter une bistabilité électronique (propriétés photomagnétiques ou de molécules/chaines aimants). Les systèmes cyanuré {FeCo} sont particulièrement adaptés pour l'observation de réarrangements électroniques thermo- et/ou photo-induit, comme en témoignent le nombre important de composés cyanurés photomagnétiques dans la littératureThe work presented in this PhD dissertation focuses on the synthesis and the characterisation of octahedral iron(II) and iron(III) complexes coordinated by a tridentate ligand of the scorpionate family (fac- geometry) and three cyanide ligands. Their use as metalloligands in respect to partially blocked metal ions is studied. Because of their ambidentate character, cyanide ligands open the door to facile synthesis of heterobimetallic species. Moreover, these ligands are known to be efficient magnetic exchange interaction transmitter, thus favouring intramolecular electronic communication between the metal ions they are bridging. The functionalisation of scorpionate ligands allows control over the intrinsic electronic properties of the iron precursor complexes, thus allows to tune the properties of the obtained polynuclear species from the latter by self-assembly. In this PhD dissertation, a particular interest was taken in {FeCo} systems because of their potential ability to exhibit electronic bistability (photomagnetic properties or SMM/SCM behaviour). Cyanide-bridged {FeCo} systems are particularly suitable for the observation of thermally or light-induced electron rearrangements, as testified by the wide range of photomagnetic cyanide-bridged compounds in the literature
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Choo, Bee Khim. "Mechanisms of cyanogen reduction during fermentation of cassava." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298989.
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Wood, Andrew John. "Mixed-metal complexes incorporating redox-active cyanomanganese ligands." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311404.
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Meehan, Samantha. "The fate of cyanide in groundwater at gasworks sites in South-Eastern Australia /." Connect to thesis, 2000. http://eprints.unimelb.edu.au/archive/00000229.
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Ishibashi, Eisuke. "Asymmetric addition of cyanide to aldehydes and imines." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1185.
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Cyanohydrins are a group of compounds that are widely used in industry as common building blocks for asymmetric synthesis. In this thesis, novel methods of synthesizing chiral cyanohydrins are investigated using complexes of transition metals complexed to salen ligands. To start the project, alternative sources of cyanide were investigated. Unfortunately, this investigation could not uncover a new cyanide source that was more effective than trimethylsilyl cyanide as a substrate for titanium(salen) based catalysts. However, this research has led to the finding that KCN / 18-Crown-6 can be used as a co-catalyst in the addition of ethyl cyanoformate to various aldehydes. This has led to a huge reduction in the amount of catalyst that is required to achieve the same enantiomeric excess. In addition, the diastereoselective synthesis of cyanohydrin derivatives using chiral cyanoformates was made possible for the first time. Some of the cyanohydrins synthesized by the new ethyl cyanoformate route were taken a step further, and their use as chiral building blocks was also studied. By using a palladium based catalyst, α,β,-unsaturated cyanohydrins were converted into amides via a two-step reaction. Research into the Strecker reaction was also carried out using vanadium(V)(salen) complexes as catalysts. In this field, the use of phenols as co-catalysts was discovered, and this has led to a world leading enantiomeric excess.
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文玉蘭 and Yuk-lan Catherine Man. "Cyanide waste management: technologies, economic aspects, and constraints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31253507.
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Mlingi, Nicholas L. V. "Cassava processing and dietary cyanide exposure in Tanzania." Doctoral thesis, Uppsala universitet, Medicinska fakulteten, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-115130.
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Duke, C. V. A. "The study and application of supported cyanide reagents." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374163.
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Man, Yuk-lan Catherine. "Cyanide waste management : technologies, economic aspects, and constraints /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17665346.
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Craston, Jane Sarah. "Biochemical effects of chronic cyanide exposure in the chicken and their relevance to the mechanism by which cyanide alleviates selenium toxicity." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46733.
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Lotter, Nadia. "Cyanide volatilisation from gold leaching operations and tailing facilities." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-04162007-153634.
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Hodgson, Martin. "Studies of the catalysis of cyanide addition and substitution." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6409/.
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The chiral diphenylphosphinites of menthol and binaphthol have been prepared. The zerovalent palladium complexes of these phosphinites were found to be poor catalysts for the hydrocyanation of alkenes. The enantiomeric purity of the exo-norbornane carbonitrile produced from the hydrocyanation of norbornene catalysed by Pd(DI0P)(_2) was found to be considerably lower than originally surmised. In the same reaction, the zerovalent palladium complexes of BPPM and BINAP were found to give the highest reported enantiomeric purities for a transition metal catalysed hydrocyanation reaction. The mechanism of transition metal catalysed asymmetric hydrocyanation was examined. Preliminary mechanistic investigations were conducted using (DIOP) platinum(O) alkene complexes. The formation of a platinum hydrido cyanide complex was observed by (^i)H and (^31)P N.M.R. spectroscopy. The novel complex (DIOP) palladium(O) ethene has been prepared and isolated, yielding the first crystal structure of a palladium ethene complex. Oxidative addition of HCN to the complex generated (DIOP) palladium hydrido cyanide. The complex also underwent other oxidative addition reactions; some may involve one electron processes. The use of PNP salts to effect the introduction of CN" by addition or substitution reactions is described. The salts are particularly suited to reactions with hydrolysis sensitive substrates. The salts are used under both phase transfer and stoichiometric conditions.
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Cheyne, Simon M. "Total neutron diffraction studies of disordered cyanide crystal structures." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402196.
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