Distillation Recovery of Tellurium from Copper Telluride in Oxide Forms

The results of study aimed at extraction of tellurium from its compound with copper in the form of oxides by the pyrometallurgical method are presented in the paper. Technical copper telluride of Kazakhmys Corporation LLP containing crystalline phases (%) 36.5 Cu₇Te₄, 28.5 Cu₅Te₃, 12.9 Cu₂Te, 16.2 Cu_2.5SO₄(OH)₃·2H₂O, and 6.0 Cu₃(SO₄)(OH)₄ was used as an object of research. As a result of the physical and chemical research and technological experiments, the fundamental possibility of processing technical copper telluride by oxidative distillation roasting with the extraction of tellurium into a separate product has been shown. Air oxygen was used as an oxidant. It has been established that a pressure decrease in the range of 80–0.67 kPa at the same temperature entails an increase in the degree of tellurium extraction. However, from a technological point of view, the value of the degree of tellurium extraction (93.0–98.0%) at all pressures (within 1 h) is achieved at a temperature of 1100°C. Increasing the exposure to 3 h has a minor beneficial effect. Diffractometric studies of cinders from technological experiments showed a decrease in the content of copper oxides in the pressure range of 80–40 kPa and an increase in the content of the Cu₃TeO₆ phase. With a subsequent increase in rarefaction from 40 to 0.67 kPa, there is a noticeable decrease in the amount of cuprite and, as a consequence, a sharp increase in the amount of cuprous oxide. A slowdown in the increase in the amount was noted for copper tellurate at pressures of 40–20 kPa, and a sharp drop in its content was noted at pressures below 13.3 kPa. The derived condensate is a free-flowing mixture of crystalline phases of tellurium dioxide (67.7%) and tellurium oxysulfate (32.3%). This condensate is a middling product for further production of elemental tellurium.