Tesi sul tema "Chlorine"

Four commercially available methods used for the analysis of low-level Chlorine Dioxide (ClO2) concentrations in drinking water were evaluated for accuracy and precision and ranked according to cost, efficiency and ease of the methods under several conditions that might be encountered at water treatment plants. The different analytical methods included: 1.The DPD (N, N-diethyl-p-phenylenediamine) method 2.Lissamine Green B (LGB) wet-chemical method 3.Palintest® kit LGB 4.Amperometric titration All these tests were performed with standard 1.0 mg/L ClO2 either alone or in the presence of different chlorine species, including chlorite ion (ClO2-, 0.5 mg/L), chlorate ion (ClO3-, 0.5 mg/L) and chlorine (Cl2, 1.0 mg/L). The tests were performed with four different matrices, with different concentrations of 0.1 mg/L ClO2, 0.5 mg/L ClO2 and 1.0 mg/L ClO2 at a constant temperature of 20oC and at different temperatures of 0oC, 10oC and 20oC at a fixed ClO2 concentration of 1.0 mg/L. None of the four methods produced the desired level of either accuracy or precision. For all four methods, interference to the measured ClO2 concentration from the addition of ClO2-, ClO3-, and Cl2 was minimal when the methods were performed according to specifications. The Palintest® was the best all-round method because it was easy to perform, performed well at all concentrations tested, and its colored product was stable. The HACH® DPD method was also easy to perform and gave the best results when measuring concentrations of 1.0 mg/L ClO2. The DPD method was less accurate than the Palintest® at lower concentrations. The DPD colored product that formed upon reaction of ClO2 and DPD was unstable, making it necessary to measure the intensity of the colored product at exactly 1 minute. The amperometric titration and lissamine green methods were more cumbersome and time-consuming to perform than either the DPD or Palintest® methods; for this reason they are less desirable for routine use.
Master of Science

Chlorine dioxide (ClO₂) was included in the Spring Hollow Water Treatment Plant (Roanoke County, Virginia) to oxidize manganese and iron, prevent tastes and odors, and avoid the formation of excessive halogenated disinfection by-products. A state-of-the-art, gas:solid ClO₂ generation system manufactured by CDG Technology, Inc. was installed at the plant and is the first full-scale use of this technology in the world. The ClO₂ generator produces a feed stream free of chlorine, chlorite ion (ClO₂⁻), and chlorate ion (ClO₃⁻), resulting in lower by-product concentrations in the treatment system The objectives of this project were to study ClO₂ persistence and by-product concentrations throughout the treatment plant and distribution system and to evaluate granular activated carbon (GAC) columns for removing ClO₂⁻ from the finished water. The ClO₂ dosages applied during this study were relatively low (<0.75 mg/L), and, as a result, ClO₂⁻ concentrations never approached the maximum contaminant level (MCL) (1.0 mg/L). Likewise, the plant effluent ClO₂ concentration never approached the maximum residual disinfectant level (MRDL) (0.80 mg/L), but concentrations as high as 0.15 mg/L reformed in the distribution system by ClO₂⁻ reaction with chlorine. Chlorate ion was monitored despite the fact that no ClO₃⁻ MCL has been proposed, and concentrations were quite low (never greater than 0.10 mg/L) throughout the treatment plant and in the distribution system. The reasons for the low concentrations are that ClO₃⁻ is not produced by the gas-solid generator used at the facility and ClO₂⁻ concentrations in the clearwell prior to chlorination were uniformly low. The average ClO₂⁻ reduction upon passage of treated water through the GAC contactor was approximately 64 percent, but the GAC effectiveness was declining over the six-month study period. Apparently, GAC effectiveness, as shown by others, is short-lived, and if higher ClO₂ dosages are ever applied at the Roanoke County facility, the ClO₂⁻ concentrations will have to be reduced by either ferrous coagulants or reduced-sulfur compounds. Regenerated ClO₂ concentrations in the distribution system were below 0.2 mg/L, but concentrations as low as 0.03 mg/L were found at homes of customers who complained of odors. During this study, twelve complaints were received from eight customers, and each complainant had recently installed new carpeting, which has been shown to contribute volatile organics that react with ClO₂ to produce odors similar to kerosene and cat urine. While meeting the Cl₂ MCL likely will be no problem if the ClO₂ dose at the plant remains below 1.0 mg/L, the problem of offensive odors in the distribution system will likely continue as long as any ClO₂ is in the finished water when chlorine is present.
Master of Science

Interactions between copper and chlorine disinfectants were examined from the perspective of disinfectant decay and copper pitting corrosion. Sparingly soluble cupric hydroxide catalyzed the rapid decay of free chlorine, which in turn, led to production of less soluble and more crystalline phases of cupric hydroxide. The catalytic activity of the cupric hydroxide was retained over multiple cycles of chlorine dosing. Experiments with chloramine revealed that copper species could also trigger rapid loss of chloramine disinfectant. In copper pipes, loss of free chlorine and chloramine were both rapid during stagnation. Reactivity of the copper to the disinfectants was retained for weeks. Phosphate tended to decrease the reactivity between the copper pipe and chlorine disinfectants. A novel, inexpensive and real-time test to monitor copper pitting corrosion was developed. In a normal pipe, it is not possible to measure the electron flow or pitting current from the pit anode to the cathode. But a new method was developed that can form an active pit on the tip of a copper wire, which in turn, allows the pitting current to be measured. Preliminary experiments presented herein have proven that this technique has promise in at least one water condition known to cause pitting. The method also quickly predicted that high levels of orthophosphate could stop pitting attack in this water, whereas low levels would tend to worsen pitting. Future research should be conducted to examine this technique in greater detail.
Master of Science

The purpose of this study was to identify the effect that water quality, pipe material, pipe size, flow conditions and the use of corrosion inhibitors would have on the rate of free chlorine and chloramine decay in distribution systems. Empirical models were developed to predict the disinfectant residual concentration with time based on the parameters that affected it. Different water treatment processes were used to treat groundwater and surface water to obtain 7 types of finished waters with a wide range of water quality characteristics. The groundwater was treated either by conventional treatment by aeration (G1) or softening (G2) or high pressure reverse osmosis (RO) and the surface water was treated either by enhanced coagulation, ozonation and GAC filtration (CSF-O3-GAC or S1) or an integrated membrane system (CSF-NF or S2). The remaining two water types were obtained by treating a blend of G1, S1 and RO by softening (S2) and nanofiltration (G4). A pilot distribution systems (PDS) consisting of eighteen (18) lines was built using old pipes obtained from existing distribution system. The pipe materials used were polyvinyl chloride (PVC), lined cast iron (LCI), unlined cast iron (UCI) and galvanized steel (G). During the first stage of the study, the 7 types of water were blended and fed to the PDS to study the effect of feed water quality changes on PDS effluent water quality, and specifically disinfectant residual. Both free chlorine and chloramines were used as disinfectant and the PDSs were operated at hydraulic retention times (HRT) of 2 and 5 days. The PDSs were periodically tested for free and combined chlorine, organic content, temperature, pH, turbidity and color. The data obtained were used to develop separate models for free chlorine and chloramines. The best fit model was a first-order kinetic model with respect to initial disinfectant concentration that is dependent on the pipe material, pipe diameter and the organic content and temperature of the water. Turbidity, color and pH were found to be not significant for the range of values observed. The models contain two decay constants, the first constant (KB) accounts for the decay due to reaction in the bulk liquid and is affected by the organics and temperature while the second constant, KW, represents the reactions at the pipe wall and is affected by the temperature of the water and the pipe material and diameter. The rate of free chlorine and chloramine decay was found to be highly affected by the pipe material, the decay was faster in unlined metallic pipes (UCI and G) and slower in the synthetic (PVC) and lined pipes (LCI). The models showed that the rate of disinfectant residual loss increases with the increase of temperature or the organics in the water irrespective of pipe material. During the second part of the study, corrosion control inhibitors were added to a blend of S1, G1 and RO that fed all the hybrid PDSs. The inhibitors used were: orthophosphate, blended ortho-polyphosphate, zinc orthophosphate and sodium silicate. Three PDSs were used for each inhibitor type, for a total of 12 PDSs, to study the effect of low, medium and high dose on water quality. Two PDSs were used as control, fed with the blend without any inhibitor addition. The control PDSs were used to observe the effect of pH control on water quality and compare to the inhibitor use. One of the control PDSs (called PDS 13) had the pH adjusted to be equal to the saturation pH in relation to calcium carbonate precipitation (pHs) while the pH of the other control PDS (PDS 14) was adjusted to be 0.3 pH units above the pHs. The disinfectant used for this part of the study was chloramine and the flow rates were set to obtain a HRT of 2 days. The chloramine demand was the same for PDS 14 and all the PDSs receiving inhibitors. PDS 13 had a chloramine demand greater than any other PDS. The lowest chloramine demand was observed in PDS 12, which received silicate inhibitor at a dose of 12 mg/L, and presented the highest pH. The elevation of pH of the water seems to reduce the rate of decay of chloramines while the use of corrosion inhibitors did not have any effect. on the rate of chloramine decay. The PDS were monitored for chloramine residual, temperature, pH, phosphate, reactive silica, and organic content. Empirical models were developed for the dissipation of chloramine in the pilot distribution systems as a function of time, pipe material, pipe diameter and water quality. Terms accounting for the effect of pH and the type and dose of corrosion inhibitor were included in the model. The use of phosphate-based or silica-based corrosion inhibitors was found to have no effect on the rate of chloramine dissipation in any of the pipe materials. Only the increase of pH was found to decrease the rate of chloramine decay. The model to best describe the decay of chloramine in the pilot distribution systems was a first-order kinetic model containing separate rate constants for the bulk reactions, pH effect and the pipe wall reactions. The rate of chloramine decay was dependent on the material and diameter of the pipe, and the temperature, pH and organic content of the water. The rate of chloramine decay was low for PVC and LCI, and more elevated in UCI and G pipes. Small diameter pipes and higher temperatures increase the rate of chlorine decay irrespective of pipe material. Additional experiments were conducted to evaluate the effect of flow velocity on chloramine decay in a pilot distribution system (PDS) for different pipe materials and water qualities. The experiments were done using the single material lines and the flow velocity of the water was varied to obtain Reynolds' numbers from 50 to 8000. A subset of experiments included the addition of blended orthophosphate corrosion inhibitor (BOP) at a dose of 1.0 mg/L as P to evaluate the effect of the inhibitor on chloramine decay. The effect of Reynolds' number on the overall chloramine decay rate (K) and the wall decay rate constant (W) was assessed for PVC, LCI, UCI, and G pipes. PVC and LCI showed no change on the rate of chloramine decay at any flow velocity. UCI and G pipes showed a rapid increase on the wall decay rate under laminar conditions (Re < 500) followed by a more gradual increase under fully turbulent flow conditions (Re > 2000). The use of the BOP inhibitor did not have an effect on the rate of chloramine decay for any of the pipe materials studied. Linear correlations were developed to adjust the rate of chloramine decay at the pipe wall for UCI and G depending on the Reynolds' number.
Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering PhD

The reaction between o-phenylenediamine and 2,3-dichloromaleic anhydride has been probed and found to give 2,3-dichloropyrrolo[1,2-a]- benzimidazol-1-one as the major product. Chlorine substitution in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one by added benzylthiol occurs in the presence of pyridine to provide the corresponding monosulfide and disulfide derivatives. The first benzylthiol ligand undergoes reaction at the C-3 position of the five-membered pyrrolo-1-one ring, with the addition of the second benzylthiol ligand occurring at the remaining chlorine-substituted carbon. The mono- and disulfide derivatives have been isolated and characterized in solution by NMR, IR, and UV-vis spectroscopies, and the solid-state structure of 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one has been established by X-ray crystallography.

Chlorine (C12(sq»' chlorine dioxide (Cl02 ) and potassium permanganate (KMn04) were evaluated as oxidants for the removal of grassy and cucumber odors associated with the pure compounds, cis-3-hexenol and trans-2, cis-6-nonadienal, respectively, and for the removal of fishy odors associated with a culture of an alga, Synura petersenii. The effects of the oxidants on the pure compounds were assessed both by Flavor Profile Analysis (FPA) and gas chromatography/mass spectrometry (GC/MS). The effects of the oxidants on the algae culture were evaluated by FPA only. In addition, an unoxidized sample of Synura petersenii was analyzed by gas chromatography coupled with mass spectrometry (GC/MS) for possible identification of fishy-smelling compounds. Chlorine (1-6 mg/L) and KMn04 (0.25-4 mg/L) markedly reduced grassy and cucumber odors associated with the two compounds. Gas chromatography/mass spectrometry confirmed that these compounds were reduced to below method detection limits. Levels of C12(&q) required (up to 6 mg/L) to reduce the grassy odors associated with cis-3-hexenol were higher than those of KMno4 ⠢ The high C12(&q) doses may have contributed to the formation of chemical odors observed by panelists. Two isomers of chlorohexenol were confidently identified as byproducts of cis-3-hexenol chlorination and may have contributed to the chemical odors that developed after CI2(aq) treatment. Chlorine and KMn04 (both at 10 mg/L) either reduced or destroyed the fishy odor associated with the culture of Synura petersenii; however, oxidation caused either the development or unmasking of fruity, cucumber, melon and grassy odors. Chlorine dioxide (3 mg/L) did not reduce the grassy and cucumber odors associated with cis-3-hexenol and trans-2, cis-6-nonadienal , respectively. Gas chromatography and mass spectrometry confirmed that concentrations of these compounds were not reduced to below method detection limits. Furthermore, at a concentration of 10 mg/L, CI02 did not effectively reduce either the fishy or other objectionable odors associated with Synura petersenii culture. Hexanal, with an odor described as "green" or "like lettuce heart," and trans-2, cis-6-nonadienal (cucumber odor) were confirmed as algal products in a two-week-old culture of Synura petersenii. In addition, decatrienal was confidently identified as a product of Synura and may have contributed to the fishy odor associated with this alga.
Master of Science

Chlorinated organic compounds (Clorg) are produced naturally in soil. Formation and degradation of Clorg affect the chlorine (Cl) cycling in terrestrial environments and chlorine can be retained or released from soil. Cl is known to have the same behaviour as radioactive chlorine-36 (36Cl), a long-lived radioisotope with a half-life of 300,000 years. 36Cl attracts interest because of its presence in radioactive waste, making 36Cl a potential risk for humans and animals due to possible biological uptake. This thesis studies the distribution and cycling of chloride (Cl–) and Clorg in terrestrial environments by using laboratory controlled soil incubation studies and a forest field study. The results show higher amounts of Cl– and Clorg and higher chlorination rates in coniferous forest soils than in pasture and agricultural soils. Tree species is the most important factor regulating Cl– and Clorg levels, whereas geographical location, atmospheric deposition, and soil type are less important. The root zone was the most active site of the chlorination process. Moreover, this thesis confirms that bulk Clorg dechlorination rates are similar to, or higher than, chlorination rates and that there are at least two major Clorg pools, one being dechlorinated quickly and one remarkably slower. While chlorination rates were negatively influenced by nitrogen additions, dechlorination rates, seem unaffected by nitrogen. The results implicate that Cl cycling is highly active in soils and Cl– and Clorg levels result from a dynamic equilibrium between chlorination and dechlorination. Influence of tree species and the rapid and slow cycling of some Cl pools, are critical to consider in studies of Cl in terrestrial environments. This information can be used to better understand Cl in risk-assessment modelling including inorganic and organic 36Cl.
Klorerade organiska föreningar (Clorg) bildas naturligt i mark och påverkar klorets kretslopp genom att de stannar kvar längre i marken. Detta stabila klor anses ha samma egenskaper som klor-36, som är en långlivad radioisotop med en halveringstid på 300 000 år. Klor-36 förekommer i olika typer av radioaktivt avfall och om klor-36 sprids i naturen finns det en potentiell risk för människor och djur genom biologiskt upptag. Syftet i denna avhandling är att öka kunskapen om fördelningen och cirkulationen av klorid (Cl-) och Clorg i terrestra miljöer med hjälp av studier i laboratoriemiljö samt en fältstudie i skogsmiljö. Resultaten visar att bildningshastigheten av Clorg är högst i barrskogsjord och rotzonen tycks vara en aktiv plats. Det finns också en större mängd Cl- och Clorg i barrskogsjordar än i betesmark och jordbruksmark. Den mest betydande faktorn som styr halterna av Cl- och Clorg är trädsort, medan geografiskt läge, atmosfäriskt nedfall, och jordmån är av mindre betydelse. Bildning och nedbrytning av Clorg sker med liknande hastigheter, men det tycks finnas två förråd av Clorg i jorden varav ett bryts ner snabbt och ett mer långsamt. Bildningshastigheten av Clorg är lägre i jordar med höga halter av kväve medan nedbrytningshastigheterna inte påverkas av kväve. Slutsatsen från studiernas resultat är att klor i hög grad är aktivt i mark och att Cl- och Clorg halterna bestäms av en dynamisk jämvikt mellan bildning och nedbrytning av Clorg. I studier av klor i terrestra miljöer bör trädsorters inverkan och nedbrytning av olika klorförråd beaktas då det kan ge varierande uppehållstider av Cl- och Clorg i mark. Denna information är viktig vid riskbedömningar av hur radioaktivt klor kan spridas och cirkulera vid en eventuell kärnkraftsolycka.

The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.

Microbes have been suggested to have a strong impact on the transportation of chlorine in soils. There are speculations about environmental factors limiting microbial effect on chlorine movement and retention. For this study, a numerical hydrochemical model was built to describe microbial transformation of chlorine in a laboratory lysimeter experiment. Undisturbed soil cores used to set-up the experiment were collected from a coniferous forest soil in southeast Sweden. The lysimeters were modelled in groups depending on their different water and chloride treatments. Microbial transformation of chlorine was better described under high water residence times and high chloride loads compared to low water residence times and low chloride loads. Microbial activity was also shown to properly account for a sudden shift from net-chlorine retention to net chlorine release in most of the lysimeters. Oxygen proved to be very important in accounting for the short-term shift from chloride retention to release in all the lysimeters. Model outcome revealed that 0.02– 0.10 mg Cl- could be available per day in a coniferous soil depending on season and other soil conditions. This study shows that modeling enable a better understanding of chlorine biogeochemistry. It also confirms the speculated importance of microbial activities on chloride availability in soils.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2005.
Vita.
Includes bibliographical references (p. 108-111).
The objective of this work is to functionalize an existing polymer such that it better mimics natural tissue for tissue growth and regeneration. Numerous other processes have tried and accomplished this by non-specific protein adsorption, covalent attachment, biomolecule entanglement, and synthesis of new polymers with the desired functionality. The focus of this work is to modify the polymer's binding capability to cells while not altering the bulk properties. Through the use of both phage display of peptide libraries and yeast surface display of scFv libraries the surface of chlorine-doped polypyrrole (PPyCl) has been modified to facilitate binding of neuronal phenotype cells. The selection of peptides using phage display found a surface specific recognition peptide (T59) that was made bivalent by altering the C-terminus with an integrin binding epitope. The bivalency of the modified T59 peptide was exploited to tether phenochromocytoma (PC12) cells to the surface of PPyCl. Furthermore the tethering of the cells to PPyCl through the peptide does not decrease the cells neuronal function and maintains the bulk conductive polymers characteristics. Using the peptide as a bivalent linker, the addition of other types of cells, drugs, growth factors, and enzymes could be incorporated for various biomedical applications.
(cont.) An antibody (Y2) specific to PPyC1 was found using yeast surface display. This antibody was utilized to mediate cellular binding to PPyCl by expression of the antibody on the surface of PC12 cells. Complimenting the peptide studies of having an exterior bivalent linker the antibody recognition provides the means for any cell type to adhere to PPyCl, through expression of the antibody on the surface of the cell. This type of system could be used for various types of tissue growth supports.
by Kiley Preston-Halfmann Miller.
Ph.D.

This thesis work is the continuation and final part of a joint project between the Department of Materials Technology, NTNU and Norsk Hydro Research Center in Porsgrunn, looking at the possibility of using fuel cells for production of hydrogen chloride and electric power. The experimental work encompass an evaluation of three hydrogen - chlorine fuel cell design concepts, development and implementation of a mathematical fuel cell model and a kinetic study of the chlorine reduction reaction.

The evaluated fuel cell designs consisted of a) a conventional PEM fuel cell applying a Nafion membrane, b) a composite system applying an aqueous HCl electrolyte and Nafion membrane and c) a phosphoric acid doped PBI membrane fuel cell operating at intermediate temperatures of 150 - 175 ◦C. From the evaluation it was found that the chlorine reduction kinetics are much faster than the corresponding oxygen reduction reaction, leading to low activation losses on the fuel cell cathode. However, the nature of the reactant, chlorine, and the product, HCl, places strict demands on the corrosion resistance of the construction materials and drastically increases the difficulties related to water management in the cells. Due to these effects, none of the investigated systems were able to demonstrate stable operation under the conditions used in this study. The PBI cell showed best potential and seems to be the system in which the humidification and corrosion difficulties easiest can be remedied. The first design criteria for such a system should be the minimisation of the existence of liquid water, ideally a hydrogen - chlorine fuel cell system should operate in totally water free environment and consist of a high temperature proton conductor.

A two dimensional, isothermal mathematical model of a hydrogen - chlorine single fuel cell with an aqueous HCl electrolyte is presented. The model focuses on the electrode reactions in the chlorine cathode and also includes the mass and momentum balances for the electrolyte and cathode gas diffusion layer. There is good agreement between the model predictions and experimental results. Distributions of physical parameters such as reactant and product concentrations, solution and solid phase potentials and local current densities and overpotentials as a function of cell voltage are presented. Effects of varying the initial electrolyte concentration and operating pressure are analysed. It was found that an electrolyte inlet concentration of 6 mol dm−3 gave the best cell performance and that an increase of operating pressure gave a steady increase of the fuel cell performance.

The rate and mechanism of the electroreduction of chlorine on electrochemically oxidised Pt and Ru electrodes has been investigated relative to the state of oxide formation. Current/potential curves for the reduction process in 1 mol dm−3 HCl solution saturated with Cl2 have been obtained for electrode surfaces in various states of preoxidation with the use of the rotating disc electrode technique (RDE). In the case of chlorine reduction on platinum, the results indicate that adsorption of chlorine molecules with a subsequent rate determining electrochemical adsorption step is the dominant mechanism. The exchange current density seems to decrease linearly with the logarithm of the amount of surface oxide. Chlorine reduction on ruthenium is best described by a Heyrovsky-Volmer mechanism with the first charge transfer reaction as the rate determining step. The Krishtalik mechanism incorporating adsorbed O•Cl+ intermediates is also able to describe the reaction successfully. The reaction order is constant for all oxide coverages while the exchange current density apparently moves through a maximum at intermediate oxide coverages (∼100 mC cm−2). The results show that the electrocatalysis of the cathodic reduction of chlorine is very sensitive to the state of the oxidation of the electrode surface.

The rate and mechanism of the electroreduction of chlorine on electrooxidised ruthenium has further been investigated with focus on the effect of solution pH. Current/potential curves for the reduction process in solutions with constant chloride concentration of 1.0 mol dm−3 and varying H+ concentration have been obtained with the use of the rotating disk electrode technique (RDE). It was found that the chlorine reduction rate is highly inhibited in solutions with high H+ concentrations and that it can be satisfactorily described by the Erenburgh mechanism, previously suggested for the chlorine evolution on RuO2 and ruthenium titanium oxides (RTO). The expression of the kinetic current as a function of chlorine and H+ concentration was obtained by solving the elementary rate equations of the kinetic mechanism. The kinetic constants obtained from the correlation of the kinetic current expression to the experimental data were used to simulate the dependence of the surface coverages and elementary reaction rates on overpotential.

The amount of corrosion of six metal samples was measured by a change in weight over time. The simulated flue gas stream consisted of 0.2% SO2,14% C02 / and 4% O2, with the HC1 percentage varied from 0.2% to 0.0% and the balance of gas being N2. A Lindbergh Three Temperature Tube Furnace was used to house the metal samples at 100°C, 200°C, and 600°C while being subjected to the simulated flue gas stream. The six metal samples were chosen on the frequency of industrial use. Two carbon steels, C1018 and C1010, contain no chromium and were chosen because of their popularity in older coal combustor systems. The other four samples, F l l , F22, Alloy 800, and 310 SS, are chromium containing metals that were chosen to indicate corrosion inhibitory effects. These four chromium containing samples are commonly used for replacement parts in areas that are prone to high corrosion effects. Weight loss due to corrosion shows a direct relationship to the concentration of HC1 in the flue gas stream for the F l l , F22, and C1018 samples. The greatest amount of weight loss was seen in the 0.2% HC1 and the least for the three samples when there was no HC1 in the flue gas stream. The C1010 sample had the greatest amount of weight loss under the 0.01% HC1 concentration, slightly less for the 0.2% HC1, and finally a weight gain for the 0.0% HC1 run. At no concentration did samples Alloy 800 and 310 SS exhibit any weight change. As for temperature considerations, the greatest amount of change in the samples was seen for the 600°C runs. The 200°C run produced no change in weight for any of the samples, due to the lack of condensation that would facilitate corrosion at low temperatures. For the 100°C runs, the flue gas containing 0.2% HC1, 0.2% S02,14% SO2,4% O2, and the balance N2, caused a change in weight for F l l , F22, C1010, and C1018. This change was not as great as that for the 600°C run. The other two 100°C runs produced no change in weight. Chromium content of the metals can also be related to the amount of corrosion. The high percentage chromium metals, Alloy 800 and 310 SS, showed no weight change in any of the runs. Low chromium containing samples, Fll and F22, showed a loss of weight at all 600°C runs and also for the 100°C subjected to the 0.2% HC1 flue gas stream. The C1010 and C1018 samples contain no chromium and have the most erratic results. These samples gained in weight for the 600°C run for the 0.0% HC1 gas and lost weight for the two other 600°C runs. Also, weight loss for these samples was observed for the 100°C run under 0.2% HC1. Corrosion of the samples begins and proceeds rather quickly until an oxide layer is formed. Once the oxide layer has formed, the amount of corrosion is dependent on the stability of that layer and the diffusion rate of the gases.

A study has been made of the xerographic properties of amorphous selenium doped with chlorine at concentrations below 100 parts per million (ppm) by weight. The sample consisted, in each case, of an aluminum plate with a thin deposited r.f. sputtered aluminum oxide film, on which a 50 micrometer layer of amorphous selenium was deposited by evaporation, with a substrate temperature of 50$ sp circ$C. It was found that the chlorine decreased the acceptance voltage following corona charging, increased the dark decay rate and decreased the residual voltage after illumination discharge. The changes were such as to be beneficial xerographically for small additions of chlorine to the selenium in the ppm range. Analysis of the time derivative of the dark decay voltage indicated that depletion discharge was the dominant process in the decrease of dark decay voltage with time and a modified relation was introduced to describe the increase of bulk space charge density with time, arising from thermal excitation of holes from deep discrete centres in the photoreceptor. This analysis indicated a decrease of the release time of the holes with increase of chlorine content, whereas an observed decrease of single cycle and cycled-up residual voltages with increased chlorine indicated an increase of hole capture time from their relevant trapping centres. Capacitance and incremental resistance measurements on the aluminum oxide blocking layers indicated higher resistance in films deposited by r.f. sputtering than by d.c. reactive sputtering on aluminum substrates. However, no difference in xerographic performance could be detected between the two sputtering methods. Oxide layers were also deposited on nickel and gold substrates by r.f. sputtering.

In order to extend application of the gel-degradation mechanism of delignification, model compounds of the general structure (3,4-dimethoxyphenyl)-CH(OR)R$ sp prime$ were treated at room temperature with increasing charges of molecular Cl$ sb2$ in glacial HOAc.
Catalytic amounts of Cl$ sb2$ cleaved benzyl aryl ether bonds (OR=2-methoxy-4-methylphenoxy) before any ring chlorination occurred. Yields of cleavage decreased in the order: R$ sp prime$=H; R$ sp prime$=$-$CH$ sb2$-2-methoxyphenoxy; R$ sp prime$=$-$CH(CH$ sb2$OH)-2-methoxyphenoxy. These results support the concept that the delignification of wood pulp by chlorine results from benzyl aryl ether cleavage. The conditions of the reaction, as well as control reactions with hydrochloric acid, suggest that the cleavage is due to conventional acid hydrolysis induced by chlorine. The experimental evidence does not rule out another possible mechanism in which the cleavage is initiated by molecular chlorine.
Benzyl ether links were generally stable in models of the benzyl alkyl type, whose primary reactions were ring chlorination. A large excess of chlorine caused side-chain displacement, hitherto considered the primary reaction in the solubilization of lignin.

Chloride and ³⁶C1 from 1950's weapons testing are good tracers of recent precipitation recharge in arid environments like the Nevada Test Site. Examining the distribution of chloride in soil, rock fractures and rock matrices is a simple method to clarify the dynamics of long time averaged hydrologic processes, such as occur in unsaturated zones. In general, where infiltration is rapid, chloride gets flushed into the soil or deeper into fractures. An estimate for infiltration rates can then be obtained by finding the peak of the ³⁶C1 bomb pulse in the soil chloride. Some care should be exercised while using chlorides as tracers in layered or calcified soils. Results from a numerical model that is calibrated with soil ³⁶C1 soil data also indicate that soil moisture and chloride do not necessarily follow the same path at large soil suctions. Nonetheless, the distribution of chlorine and its isotopes in unsaturated rock appears to be a useful tool to tracing historic water movement in a fracture system and perhaps qualitatively defining the matrix diffusion potential of the rock.

A numerical model has been developed, based on an implicit finite difference technique, for the solution of a set of coupled non-linear partial differential equations (based on the Nemst-Planck equation), and linear and non-linear algebraic equations. These equations govern the mass transport and homogeneous chemical reactions in a simplified membrane chlor-alkali cell anolyte compartment. Membrane chlor-alkali cells are used for the industrial production of chlorine and sodium hydroxide, by electrolysis of brine. The model has been developed in an attempt to gain insight into the very localised chemistry which occurs in the hydrodynamic boundary layers within the electrolyser; chemistry which is strongly suspected to have a significant influence on the bulk chemistry, particularly on the homogeneous reactions leading to loss of chlorine through the formation of thermodynamically stable unwanted by-products such as the chlorate ion. These effects are very difficult to measure experimentally, making modelling the most attractive option. A set of experiments have been performed on laboratory scale electrolysers, in an attempt to characterise the cell chemistry, and produce data for model validation. Results are presented from the model demonstrating that the numerical approach adopted produces stable and physically plausible results under a range of operating conditions. It also demonstrates that the chemistry in both the anode and membrane hydrodynamic boundary layers differs significantly from that in the bulk. The experimental work has provided valuable insight into the mechanism of the loss reactions. Results of the experimental work are also compared with the results of the modelling.

Chlorine is an element commonly found in the environment of our planet, in the atmosphere, the earth crust and the oceans. Chlorine occurs in two forms, inorganic chloride (Cl_in) and organically bound chlorine (Cl_org), also called organochlorine. For a long time, the organic halogens (among them the organic chlorine) had been considered as produced only by human activities. However, the research of the recent decades suggests a considerably amount of naturally produced organic chlorine in soil and water. Through the research, a hypothesis have emerged, suggesting that there occur a formation of organic chlorine in the top soil layer where chloride is consuming, while the organic chlorine is degrading on deeper soil levels, causing a release of chloride. The study in this thesis attempts to explore the transportation of organic chlorine through soil. 49 soil water samples were collected at three transects, S04, S12 and S22, nearby a stream in northern Sweden and analysed for Cl_org, using an AOX-analyser. The results suggest a decrease in concentrations of Cl_org by soil depth for transects S04 and S12. The study also indicates that concentrations of Cl_org are decreasing with increasing distance from the stream, where the highest mean concentration was found in the organic matter-rich riparian transect S04. Further conclusions are that the spring flood and changes in groundwater level may influence the concentrations of Cl_org.

Ämnet klor är vanligt förekommande på vår planet och finns både i atmosfären, jordskorpan och världens oceaner. Klor uppträder i två olika former: oorganisk klorid (Cl_in) och organiskt bundet klor (Cl_org). De organiska halogenerna (bland vilka organiskt klor ingår) har under lång tid ansetts härstamma från enbart antropogena källor. De senaste decenniernas forskning har dock tytt på en naturlig produktion av organiskt klor i mark och vatten. Genom denna forskning har en hypotes tagit form som föreslår en bildning av organiskt klor i de övre marklagren, där klorid binds, medan det i djupare marklager sker en nedbrytning av det organiska kloret vilket medför ett frigörande av klorid. Denna studie syftar till att studera transporten av organiskt klor genom mark. 49 stycken markvattenprover insamlades vid tre provpunkter (S04, S12 och S22) på ett avrinningsområde i norra Sverige och analyserades med hjälp av ett AOX-instrument. Resultaten tyder på en minskning av Cl_org med ökande markdjup för provpunkterna S04 och S12. Studien visar även en minskning i koncentration av organiskt klor med ökande avstånd till vattendraget, där den högsta medelkoncentrationen återfanns i provpunkten S04 som ligger nära bäcken och är rik på organiskt material. Vidare slutsater är att vattenflödena under vårflod samt variasionen i grundvattennivå har en påverkan på koncentrationerna av Cl_org.