THE EXTRACTION OF ZINC FROM WILLEMITE BY CALCIFIED-ROASTING AND AMMONIA-LEACHING PROCESS BASED ON PHASE RECONSTRUCTION

摘要

Willemite is typically found in oxidized zinc ores and metallurgical secondary resources but without effective extraction method yet. Based on the ideas of zinc phase reconstruction in the willemite, the extraction of zinc from willemite by calcified-roasting using CaO as additive and ammonia-leaching process was studied in this paper. The influences of CaO dosage, roasting temperature, roasting time on the phase transformation and zinc leaching rate were studied, which were characterized by XRD. The results indicated that Zn_2SiO_4 was transformed into ZnO or Zn_2CaSi_2O_7 .After roasted with 1.4 times of theoretical CaO dosage at 1280 °C for 40 minutes, willemite was thoroughly transformed into ZnO. The zinc leaching rate of the roasted sample was 97.45% in NH_4Cl-NH_3·H_2O leaching system, which increased by 91.40 % compared with zinc leaching rate of 6.05% when willemite was directly leached in NH_4Cl-NH_3·H_2O system.