Thermodynamics and kinetics study of tellurium removal with cuprous ion

• The kinetics and thermodynamics of the tellurium removal by cuprous ion reduction were investigated.
• The mechanism of tellurate reduction and its corresponding rate law was suggested.
• Effects of temperature and acidity on tellurium removal rate were studied.

The chemistry and kinetics of the removal of tellurium from copper sulphate-sulphuric acid solution by cuprous ion reduction and precipitation were studied. The TeVI reduction reaction order with respect to cuprous and tellurium concentration was investigated at an acidity range of 10–100 g/L H2SO4 and at temperatures of 75 °C–95 °C. The reduction reaction mechanism, a suggested rate determining step and a rate law were offered accordingly for reduction of TeVI with cuprous. The kinetics fit the simple rate equation of −dTeVIdt=k1Cu+TeVI. A plausible TeVI reduction with cuprous was suggested via slow reduction of H6TeO6 to TeO(OH)+ followed by faster reduction of TeO(OH)+ to lower tellurium oxidation states. The rate constant k1 was calculated at different sulphuric acid concentrations (10, 15, 50, 75, 100 g/L) at T = 95.2 °C. Increasing solution acidity significantly increased the tellurium reduction reaction rate. An empirical correlation of k1 = 0.0297 × [H2SO4]1.35 was found between the rate constants and the sulphuric acid concentration over the range of 10 g/L < [H2SO4] < 100 g/L. An activation energy of 70.9 kJ/mol for k1 was calculated by varying the temperature from 75 to 95 °C.