Process Studies On Producing Zinc In Ammonia Leaching Solution From Low Grade Zinc Oxide Ore

Our country has extremely abundant and enormous reserves of low grade zinc oxide ore resources.However,due to these factors,including mineral processing difficulty,low recovery,high production costs and environmental pollution,the vast majority of domestic zinc oxide ores has not been exploited.Aiming at the present situation that low grade zinc oxide ores can't be treated effectively,This paper presents a new process of producing zinc from zinc oxide ores in the system of ammonia.Using low grade zinc oxide ores from Sichun Pingwu as raw material,it adapts enclosed,normal temperature,atmospheric pressure,circulating leaching way to get zinc-ammonia liquid,purifieation and electrowinning to produce cathode zinc was carried out.In the process,ammonia was used as leaching agent,so zinc in oxide ore was leached into solution with the form of Zn?NH₃?_i²⁺.Though these leaching process conditions,including the total ammonia concentration,mineral particle size,leaching time,temperature,liquid-solid ratio,oscillation intensity and repeatedly circulation,the thesis studies and discusses the influence of the choice of ammonia leaching process conditions and the optimization of process parameters on leaching rate.The results of leaching experiments show that the leaching efficiency of zinc oxide can reach 98%under the particle size to be 120¹80 mesh,industrial ammonia concentration to be 20²5%,the ratio of liquid to solid to be 4,oscillation intensity to be 100 r/min,leaching time to be 12 h,at ambient temperature.In the purification process,the leached solution was purified by adding zinc powder—activated carbon—oxidizing agent—precipitator.The adsorption of humic acid organic substance was effective by adding activated carbon powder.With oxidizing agent H₂O₂ and precipitator CaO,the contents of As and Sb in the leached solution was no more than 0.02 mg/L and 0.1 mg/L.After purification process,it can effectively remove the Pb,Cu,Co,Ni,Mn,Cd,As,Sb and other impurities,and the purified solution fully meet the requirements of electrochemical test.In the electrowinning process,we choose ruthenium coating titanium plate as anode,aluminum plate as cathode.the optimum electrowinning conditions are as follows:electrowinning current of 2.5A,the cell voltage of 3.3V,external temperature of 10³0?,electrode space of 3.5 cm,gelatin 0.1g/L,TP 0.1g/L,TBN 10mg/L,respectively.Under comprehensive condition experiment,the current efficiency is94.33%,and energy consumption is 2869 kW?h/t zinc,which is about 10%less than that of the traditional process.The zinc content in the eletrowinned zinc is 99.58%.New technology of ammonia leaching and electrolysis of low grade zinc oxide ore is the focus and hot of reseach in nonferrous metals industry at home and abroad,which has these advantages,including clean,environmentally friendly,energy-saving,high comprehensive utilization rate,low production costs,strong market competition.So,the new technology research of refractory low-grade oxide ore utilization has important practical significance and long-term strategic significance.