Selective Precipitation And Separation Of Polymetals In Acid Leaching Solution Of Waste Ternary Lithium Battery

Waste ternary lithium batteries are both resource and hazardous.Scientific recycling is of great significance for environmental protection and resource reuse.At present,most of the battery cathode materials use inorganic acid leaching to separate multiple metals.Precipitation separation method can not only selectively separate metal components,but also material preparation.Based on the characteristics of sulfuric acid leaching solution and hydrochloric acid leaching solution of waste ternary lithium battery cathode materials,this study combined thermodynamic equilibrium analysis,metal ion behavior analysis in solution,and solubility product constant analysis to explore two efficient multi-metal selective precipitation separation methods.The main content and research results are as follows:?1?Analyzing the Eh-pH diagram of Li-Me-H₂O series?Me=Co,Ni,Mn?,it can be concluded that Li⁺and Co²⁺are easy to separate when the concentration of Li⁺is low.Li⁺and Mn²⁺can separate when the potential of the solution system is low.Li⁺can separate from Ni²⁺in neutral or weakly alkaline solutions in the presence of reducing agents.In an alkaline environment,metal ions exist as hydroxide precipitates in the solution,and Ni?OH?₂ appears earlier than Co?OH?₂.Combined with the thermodynamic equilibrium analysis of Me-H₂O system?Me=Co,Ni,Mn?,the stability range of Mn?OH?₂ is larger than Co?OH?₂ and Ni?OH?₂.Mn²⁺can be preferentially precipitated in Me-OH^--NH₃ system,and Co²⁺,Ni²⁺,Mn²⁺have better separation effect.Ksp?MnCO₃?<Ksp?NiCO₃?<Ksp?Li₂CO₃?.In a mixed solution containing Mn²⁺,Ni²⁺,Li⁺,a carbonate precipitation agent can selectively precipitate Mn²⁺.Ksp?CoCO₃?<Ksp?NiCO₃?<Ksp?Li₂CO₃?.In acidic solutions containing Co²⁺,Ni²⁺,and Li⁺,carbonate precipitants can selectively precipitate Co²⁺.?2?A series of precipitating agent selection experiments were conducted.The results showed that when pH=5⁸,ammonium bicarbonate preferentially precipitated Mn²⁺.When pH=8¹1,Na₂CO₃ and NaOH co-precipitate Ni²⁺.When pH=11¹4,Na₂CO₃ precipitates Li⁺.When pH=7¹0,Na₂CO₃ preferentially precipitates Co²⁺.When pH=9¹2,NaOH and NH₃·H₂O co-precipitate Ni²⁺.?3?The CTTT step-by-step precipitation separation method?Ammonium oxalate-sodium carbonate-sodium carbonate&sodium hydroxide-sodium carbonate stepwise precipitation separation method?was used to separate and recover Co²⁺,Ni²⁺,Mn²⁺,and Li⁺in the acid solution.The results show that in the sulfuric acid system,under the optimal selective precipitation and separation conditions,the recovery rates of Co²⁺,Ni²⁺,and Mn²⁺are all above 93%,and the recovery rate of Li⁺is 85.21%.The mass fractions of the products are all above 96%.In the hydrochloric acid system,the recovery rates of Co²⁺,Ni²⁺,Mn²⁺,and Li⁺are all above 95%,and the mass fractions of the products are all above 95%.The ATQT step-by-step precipitation separation method?Ammonia-sodium carbonate-sodium hydroxide&ammonia-sodium carbonate stepwise precipitation separation method?was used to separate and recover Co²⁺,Ni²⁺,Mn²⁺,and Li⁺in the acid solution.The results showed that in the sulfuric acid system,under the optimal selective precipitation and separation conditions,the recovery rates of Co²⁺,Ni²⁺,Mn²⁺,and Li⁺were all above 90%.The mass fractions of the products are all above 95%.In the hydrochloric acid system,the recovery rates of Co²⁺,Ni²⁺,Mn²⁺,and Li⁺are all above 92%,and the mass fractions of the products are all above 94%.The above research results can solve the problem of polymetal recovery from secondary resources for a long time,and provide theoretical basis and technical reserves for avoiding heavy metal pollution,resource waste and sustainable development of metal materials.