Study On The Impurity Removal In Hydrometallurgical Processes Of Lithium And Nickel

The production of battery grade lithium carbonate and the arsenic deep removal from nickel sulfate electrolyte were studied in this thesis.1.A process was developed to extract carbonate directly from Zhabuye saline lake,Tibet.The Zhabuye saline lake contains high level of Li(1.14 g/L),and belongs to carbonated saline lake.It was treated by CO2 to get the bicarbonate solution,Li2CO3 dissolved according to the solubility of LiHCO3.EDTA(2-carboxyhydrazine-1,1,2-tricarboxylate)was added to chelate Ca2+ and Mg2+.Insoluble Li2CO3 was obtained from the decomposition of LiHCO3 by heating to 85 ?.Washed by hot water twice,then dried at 550? in muffle furnace,battery grade Li2CO3 was obtained.The final precipitate yielded a high purity(99.6%)and well crystalline lithium carbonate,which was determined by SEM,Thermal analysis and XRD.Pilot batches served as the basis for industrial production.The filtrate recycled 5 times in the trial process.The experiment results showed the process is effective and reliable,basically meeting the request of industrialization.The optimum operation conditions were as fellows:The battery grade Li2CO3 was produced at liquid-to-solid mass ratio of 30:1 to form Li2CO3 slurry,molar ratio of EDTA to(Ca+Mg)1.05:1 and hot water washing precipitate(L/S mass ratio 1:1)promoted ions removal.The cycle use of EDTA and filtrate avoided the loss of lithium and made large-scale production possible.This is considered an improvement as production of battery grade Li2CO3 would be easily processed.2.This project aimed at high arsenic content in nickel sulfate electrolyte from Jinchuan Group between 2012 and 2013.Arsenic in nickel electrolysis system solution was in higher concentration range(0.1 to 0.02g/L),which seriously endangered the quality of electrolytic nickel.According to the practical production of Jinchuan Group and arsenic valence from iron slag,H2O2 was added to oxidize As(?)and FeAsO4,Cu3(AsO4)2 deposition was introduced to treat arsenic removal from nickel sulfate electrolyte.Various factors affecting Fe3+,Cu2+ and AsO43-reactions were studied,the adsorption of arsenic on Fe(OH)3?Cu2(OH)2CO3?NiCO3?Na2[Fe6(SO4)4(OH)12]were tested.The results showed that arsenic removal from nickel sulfate electrolyte was carried out in the form of FeAsO4,Cu3(AsO4)2 deposition.Iron slag was analyzed on the chemical composition and structure.The results showed that Na2[Fe6(SO4)4(OH)12]was the major constituent of this slag.The valence of arsenic and iron was studied through XPS.Besides,hazard identification experiment of solid waste in arsenic from iron slag was tested,the results meet the standard of ordinary solid wastes.