Of Zn-nh <sub> 3 </ Sub>-nh <sub> 4 </ Sub> Cl System Zinc Extraction - Electrowinning Process

Lead-zinc oxide ore of Lanping is a rich zinc-containing resource in Yunnan Province. It is one of the largest lead-zinc oxide ore in the world. But the zinc grade in the ore is low, the oxidation of the ore is complete, the weathering and argillization are serious, the mineral composition is complex, multi-metals are co-existed, and the content of calcium and magnesium are high. It is difficult to extract the valuable metals economically with traditional hydrometallurgical process. Therefore, the study of "ammonia leaching-extraction-electrowinning" technique, which can deal with low-grade zinc oxide ore of high alkaine-gangue, becomes the hotspot in China.There is no special extractant for zinc currently.There has been lack of systematic study yet from ammonia leaching solutions,including the selection of zinc extractant,process of extraction and electrowinning. Therefore, two extractants, LIX84 and LIX54, are selected and experiments of extraction,stripping and electrowinning have been performed with simulated leaching solution of Lanping zinc oxide ore.The experimental results of extraction show that phase ratio, total ammonia concentration and pH are the main factors to the zinc extraction ratio.The zinc extraction ratio is up to 76.4% in the first stage of extraction experiment under the condition of 40℃, total ammonia concentration 3 mol/L,zinc ion concentration 3 g/L,[NH3]/[NH4C1]=3, the phase ratio 1:1 and the reaction time 30 min.Experimental results of co-extraction ammonia show that the content of ammonia is gradually reduced as LIX54 is increased in the organic phase. The washing methods have different effect on the washing process,while the co-extraction ammonia can be washed more completely with acidic buffer solution of certain phase ratio and pH.Stripping results show that stripping ratio is high whether pure sulfuric acid solution or sulfuric acid solution with zinc sulfate is used. The loaded organic phase with more LIX54 is more easily stripped.Effects of inorganic impurities such as Cu2+,Cd2+ and NH3,organic impurities such as ethylhexyl phosphate,β-diketones and addictives, such as strontium carbonate, on the electrolytic process have been studied.Experimental results show that the varieties of inorganic and organic impurities have different effect on the current efficiency and the quality of electrolytic zinc in the process.Product of electrolytic zinc, which can meet the quality requirements, can be obtained after the removal of these impurities and the addition of some addictives.