Carbonate Content Reduction in Zinc Ore Concentrate

Abstract

The hydrometallurgical zinc extraction from the willemite concentrate is impaired by the presence of high carbonate content. A stiff froth is produced causing zinc losses and acid consumption. A standard procedure was developed to deÞ ne the acceptable froth layer height in a laboratory test. Froth layers shorter than 2 cm resulted from carbonate content in the concentrate below 10.8%. The feasibility of adding a carbonate a otation stage to the circuit was tested in laboratory and pilot scales. Among the collectors investigated, only those presenting a saponiÞ cation degree above 189 mg KOH/mg were effective in the laboratory experiments. Oleine and rice bran oil soaps were selected for the pilot scale experiments. The Þ nal stage was a one month long industrial trial performed in a circuit consisting of three pneumatic cells G18. A comparison between the average results of the industrial trial including the carbonate a otation stage and data of the raw industrial concentrate indicated that the MgO content in the concentrate dropped from 3.7%–3%. Concurrently, the carbonate content in the concentrate dropped from 11%–10.6%, the zinc grade in the concentrate increased from 41.4%–42% and the zinc recovery increased from 86.6%–89.8%. The concentrate was processed in the hydrometallurgical plant with no frothing problems.