Study Of Resource Utilization Of The Rare-earth Ammonium Chloride Wastewater

The rare-earth chlorine ammonium wastewater, including the ammonium chlorid extraction raffinate and residual liquid of carbonate precipitation, is discharged in the production of unitary rare earth carbonate. The large number of ammonia in rare-earth wastewater not only results in the resources loss, but also causes the pollution of the surrounding ecological environment. Therefore, it is quite necessary for the enterprise to seek the effective and economical method of rare-earth wastewater treatment.This paper presented a method on rare-earth ammonium chloride wastewater recycling based on the characterization of rare-earth ammonium chloride wastewater.This method could achieve the closed circulation of wastewater and recycle ammonium chloride through auto-concentrating wastewater and evaporation crystallization with the lowest energy consumption.First,the feasibility of experimental program was verified by the research of NH4CI concentration on effect of rare-earth extraction separation.Then,the dynamic balance parameters were determined by studying the interdependence of extraction raffinate、residual liquid of carbonate precipitation and cycle number。the results showed that The wastewater cycle number was2,and each time should extract about2/5saponification wastewater to evaporation crystallization system, achieving dynamic balance of closed circulation of wastewater.Secondly, the method of coagulation and active carbon adsorption were studied to achieve the aim of further purified waste water. Coagulation sedimentation experiment showed that PAM had better purification efficiency,which proved by obvious superiority in removing metal impurities,and the removal rate of metal impurities was also above50%.Activated carbon absorption experiment implied that optimum dosage of Activated Carbon was2g and the optimum contact time was50min. And after the absorption, the oil volume could be reduced to0.2mg/L, metal impurities to0.1mg/L.Finally,the evaporation crystallization of purified wastewater was studied.And the recovered product ammonium chloride met the standard of agricultural ammonium chloride in"GB/T2946-2008",arriving at over95percent.The cost-benefit analysis showed that for1ton NH4CL recovery, the power consumption was3kWh, vapor consumption0.87-1.07t, saving water9-12t,and energy consume was reduced in60%,. Therefore, this process had many advantages such as low cost, obvious economic benefit and high environmental benefit,which was helpful to solve the problem of pollution and resources recovery of the rare-earth ammonium chloride wastewater.