Abstract：Excessive standard solution of calcium was added to precipitate oxalic acid in waste solution. After filtration, the content of oxalic acid in waste solution from rare earth separation process was determined by EDTA back titration method. The pH of sample solution was adjusted to 7.0-10.0 with 400 g/L NaOH solution. After adding 10 mL of NH3-NH4Cl buffer solution at pH 10.0, the excessive standard solution of calcium was added to precipitate the oxalic acid in waste solution. The pH of filtrate was adjusted to 12.0-12.5 with NaOH solution. The content of excessive calcium was determined by EDTA back titration with chrome blue black R as indicator. Most impurity ions in waste solution (such as RE3+, Fe3+ and Al3+) could be precipitated to hydroxides and separated under high pH. The interference of residual Fe3+ and Al3+ in filtrate with chrome blue black R indicator was eliminated by adding triethanolamine as complexing agent. The proposed method was applied to determination of oxalic acid in synthetic sample of waste solution from rare earth separation process. The results were consistent with the reference values. The proposed method was applied to determination of oxalic acid in actual sample of waste solution from rare earth separation process. The relative standard deviations (RSD, n=6) were 0.98%-1.9%. The recoveries were between 99% and 101%.
林燕, 肖观林,胡珊玲. 钙沉淀-EDTA返滴定法测定稀土分离废液中草酸[J]. 冶金分析, 2014, 34(12): 74-77.
LIN Yan,XIAO Guan-lin, HU Shan-ling. Determination of oxalic acid in waste solution from rare earth separation process by calcium precipitation-EDTA back titration. , 2014, 34(12): 74-77.
