Study On Recovery Of Oxalic Acid And Hydrochloric Acid From Rare Earth Oxalate Precipitation Wastewater

Rare earth oxides are widely used in various fields,with the transformation of rare earth industry,the scale of high purity rare earth oxides production gradually expand,the demand of international market on purity of mixed rare earth oxides is higher and higher.In order to meet the international standards,the way oxalic acid precipitation is adopt to make rare earth chloride solution produce rare earth oxalate,through washing,filtering and burning,rare earth oxalate shift high purity rare earth oxide.This process will produce waste water containing oxalic acid and hydrochloric acid.If mother liquor containing residual oxalic acid and hydrochloric acid directly return to dissolve rare earth mine,oxalic acid will combine with rare earth ions to generate oxalic acid precipitation,which can reduce the leaching rate of rare earths.Direct emissions will pollute the environment and waste of resources.According to the above problem,this paper studied on the N235-the TBP extraction method of two pieces,which realized the recycling of oxalic acid and hydrochloric acid from rare earth oxalate precipitation waste liquid.First,N235 was adopt to extract oxalic acid and hydrochloric acid from oxalic acid precipitation wastewater,the effect of extracting agent concentration,temperature,concentration of additives on the N235 extraction of oxalic acid and hydrochloric acid were inspected,the most optimal extraction conditions were determined as follows:extraction temperature is 25?,the volume fraction of N235 is 25%,volume fraction of n-octylalcohol 10%,when the stages of counter-current extraction were nine,oxalic acid extraction rate was 98%,hydrochloric acid extraction rate was 99.9%.Then,deionized water was used to reverse extraction of loaded organic phase,through adjusting phase ratio and increasing stages,oxalic acid and hydrochloric acid were enriched.Eventually,the concentration of oxalic acid and hydrochloric acid were 0.12mol/L and 0.5mol/L.The mixed solution of oxalic acid and hydrochloric acid through the N235 recycling can't reuse to ore leaching and oxalic acid precipitation process.In order to solve this problem,the TBP extraction agent for hydrochloric acid extraction rate is low,the TBP extraction agent was adopt to extract and separate oxalic acid and hydrochloric acid,the effect of extracting agent concentration,extraction temperature,concentration of HCl on TBP extraction oxalic acid was inspected.The optimized conditions:extraction temperature is 25 ?? the volume fraction of TBP is 75%,the volume fraction of sulfonated kerosene 25%,When the stage of counter-current extraction is 7,oxalic acid extraction rate reached 99.9%.The experiments of Load of oxalate organic phase stripping showed:oxalate stripping rate increased with the increase of extraction series,and decreases as compared.Finally,through stripping enrichment experiments,under different phase ratio,the maximum concentration of oxalic acid in water phase can reach 0.59 mol/L.Through the thermodynamic analysis,the extraction of oxalic acid and hydrochloric acid by N235 and the extraction of oxalic acid by TBP are related.Through infrared spectrum analysis,N235 is combined with hydrochloric acid to generate amine salt,amine salt is combined with oxalic acid and hydrochloric acid to generate ion of associating in the form of ion association.The TBP combines with oxalic acid in hydrogen bonding,belongs to the neutral complexing extraction.In this paper,the oxalic acid and hydrochloric acid in waste water of rare earth oxalate precipitation can be recycled,the certain basis was provided for the rare-earth wastewater treatment and comprehensive utilization of secondary resources.