Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we pr...Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH_4 Cl–NH_3·H_2 O solution. The thermodynamics and phase conversion of Zn_2 Si O_4 to zinc oxide(ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn_2 Si O_4 mole ratio(n(Ca O)/n(Zn_2 Si O_4)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn_2 Si O_4 was first converted to Ca_2 Zn Si_2 O_7 and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn_2 Si O_4 to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.展开更多
基金financially supported by National Program on Key Basic Research Project of China (973 Program, No. 2014CB643403)the Postdoctoral Foundation of Central South University
文摘Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH_4 Cl–NH_3·H_2 O solution. The thermodynamics and phase conversion of Zn_2 Si O_4 to zinc oxide(ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn_2 Si O_4 mole ratio(n(Ca O)/n(Zn_2 Si O_4)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn_2 Si O_4 was first converted to Ca_2 Zn Si_2 O_7 and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn_2 Si O_4 to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.
