Ferric Leaching of Low-Grade Zinc Concentrate with a Biologically Produced Solution

The process of ferric leaching of a zinc concentrate (43.3% zinc, 2.03% copper, and 13.6% iron) with a biologically produced solution has been studied. Conditions that can increase its efficiency have been found. The extraction of copper and zinc was found to increase with an increase in temperature from 25 to 80°C. The effect of pH on this process was studied, and the extraction of metals was found to decrease with a decrease in pH from 1.3 to 0.7. It was determined that the Fe 3+ concentration in the leaching solution did not affect copper recovery, while zinc recovery increased with an increase in the oxidant concentration. At a solid content in the suspension of 1%, the specific zinc leaching rate was 0.86 g/(g h), and for copper this rate was 0.46 g/(g h). These values decreased to 0.54 and 0.36 g/(g h), respectively, with an increase in pulp density of up to 10%. Thus, the parameters for effective concentrate leaching were found: a temperature of 80°C, a pH of 1.3, a solid content in the suspension equal to 10%, and an initial Fe 3+ concentration of 25.0 g/L. Under these conditions, four cycles of ferric leaching of the concentrate were carried out, as a result of which 92.3% of zinc and 51.6% of copper were extracted into the solution. The contents of zinc and copper in the solids decreased to 6.17 and 1.82%, respectively.