A New Process Study On Electrowinning Zinc In Ammonia Leaching Solution From Hanyuan Low-grade Lead-zinc Ore In Sichuan

It is very difficult to recycle of zinc for low-grade lead-zinc ore by usual processes.As a result,in the thesis,it is proposed that the new process of producing electrolytic zinc from low-grade lead-zinc ores in the system of ammonia.Using low-grade lead-zinc ores from Sichuan Hanyuan as raw material,it was leached directly from ammonia system under the condition of enclosed,normal temperature and atmospheric pressure to get ammonia leaching solution,which was purified and then to obtain high purity zinc plate by electrowinning.The optimum conditions on leaching,purification and electrowinning process were determined.In the leaching process,industrial ammonia?20%?was used as leaching agent,so zinc in ore was leached into solution with the form of Zn?NH₃?_i²⁺.The thesis studied some factors such as leaching time,liquid-solid ratio,temperature,oscillation intensity,particle size for the influence of zinc leaching rate.The optimum leaching condition was that leaching time was 18 hours;liquid-solid ratio was 5:1;temperature was normal temperature;oscillation intensity was 120r/min;and particle size was140¹80 mesh.Under the condition zinc leaching rate could reach 65.66%.The results showed that the effects of leaching time and liquid-solid ratio on the zinc leaching rate were obvious,while those of temperature,oscillation intensity and particle size were not.In order to increase the concentration of zinc per unit volume,we also conducted a number of cycle leaching experiments,and the zinc concentration could be increased to 80.2g/L.In the purification process,we firstly used oxidizing agent and precipitating agent to precipitate As and Sb,and then we used zinc powder to replace Cu,Cd,Co and so on which has higher standard electrode potential than zinc,finally we used activated carbon to adsorb humic acid organic substance to obtain a clear purified solution.The purification condition was that oxidizing agent H₂O₂?30%?was 5mL/L,and precipitator CaO was 0.1g/L;zinc powder was 10g/L;activated carbon was 6g/L;Under the condition the contents of As and Sb was decreased to 0.1mg/L and 0.03mg/L respectively,and the solution after purification fully meet electrowinning standard.In the electrowinning process,we chose titanium plate coated with ruthenium as anode and pure aluminum plate as cathode.The best condition was that current density was 300A/m²;external temperature was normal temperature,electrode space was 3.0cm;additives T-A,T-B and T-C were 0.1g/L,0.1g/L and 0.04g/L respectively.We also conducted three times comprehensive condition experiments under the best condition,and the result showed the average cell voltage was 3.1V,the average current efficiency was 94.49%and the average electric energy consumption was 2689kW?h/t zinc.Finally,we obtained the zinc plate with brght,soomth and compact,and its purity was 99.60%.In short,the study results show that this new process can recycle zinc and produce the industry-standard zinc plate,which provides a new way of thinking for the processing of low-grade lead-zinc ore,and the new process has obvious advantages:less consumption of raw materials;recycling of leaching agent;low electricity consumption;operating at room temperature;confined condition and clean environment;light purification burden;short process;less investment in equipment.So it has a reference and practical significance to recycle and reuse zinc for similar mine.