Optimisation of influential factors in electrowinning of
tellurium by means of PLS modelling

Abstract: Electrowinning of tellurium is a relatively simple process that can be
carried out effectively by employing the existing technology. In order to
obtain tellurium with the least amount of impurities, the effects of three
main factors were studied, namely current density, free concentration of
caustic soda and initial concentration of tellurium. Five elements were
chosen as the main impurities: Ag, Bi, Cd, Ni and Pb. A series of 17
experiments arranged in a CCF (central composite faced-centred) design has
been carried out and the results were fitted using PLS (partial least
squares) method. The effect of free caustic concentration was found to be
the most important of the three parameters studied. Current density was
also important, yielding the least amount of impurities at high current
densities. Tellurium concentration had the smallest effect of the three
parameters studied. From the model, current densities of 330-350 A/m2,
tellurium concentrations of 90-120 g/l and free sodium hydroxide
concentration of around 120 g/l are suggested as optimal conditions for
obtaining the purest tellurium.