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UBC Theses and Dissertations

Kinetics of selenium and tellurium removal with cuprous ion from copper sulfate-sulfuric acid solution Mokmeli, Mohammad


Dissemination of selenium and tellurium in pyritic ores and many of the sulphide minerals results in the contamination of pregnant leach solutions and electrolytes in hydrometallurgical treatment of sulphide ores and residues. In an effort to reduce the detrimental effects of selenium and tellurium, it has been of great interest to remove selenium and tellurium from contaminated solutions to lower levels than allowed in regulations, product specifications or process requirements. The selenium and tellurium content of the solution may be reduced into insoluble precipitates of copper selenides and tellurides using cuprous ion. Cuprous ion has uses as a reducing agent in hydrometallurgical applications and can be specifically used to remove selenium and tellurium ions from copper sulphate-sulfuric acid solutions. In this study, the chemistry and kinetics of the removal of selenium and tellurium from copper sulfate-sulfuric acid solutions by cuprous ion reduction and precipitation was pursued. At first, a study of equilibrium cuprous concentrations for the cupric–copper metal reaction was performed and an empirical function capable of predicting the saturated [Cu+] was suggested at different temperatures, cupric and sulfuric acid concentrations. Secondly, the kinetics of the selenium removal with cuprous was studied and the mechanism of the reduction reaction and the rate law was determined over a wide range of acidity and temperature. The effects of temperature, acidity, cupric concentration and ionic strength on selenium removal rate were also studied. Subsequently, rate constants as functions of temperature, acidity and ionic strength were suggested. Thirdly, the tellurium reduction chemistry and reaction kinetics by means of cuprous in a wide range of conditions were investigated. The mechanism of the reaction, rate constants and activation energies were also determined. Similarly to selenium, effects of temperature and acidity on tellurium removal rate were also studied and rate constants as a function of temperature and acidity were suggested. Selenium and tellurium reduction reaction times can be estimated at different acidities and temperatures using the suggested rate laws and rate constant functions.

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