Th(Ⅳ)盐沉淀-EDTA滴定法快速测定污水中总磷研究

Study on Rapid Determination of Total Phosphorus in Waste Water by Th(Ⅳ) Precipitation-EDTA Titration

研究了快速测定污水中磷含量的Th（Ⅳ）盐沉淀-EDTA滴定的分析方法。水样用HNO3及H2SO4消解为PO4^3-并在掩蔽干扰离子后的酸性溶液中，先加入已知量且过量的Th（NO3）4标准溶液．当Th、（PO4）4沉淀完全并在pH2-3滤液中。以二甲酚橙为指示剂，用乙二胺四乙酸二钠盐（EDTA）标准溶液滴定剩余的Th（NO3）4至终点、测定结果的相对标准偏差小于2．5％，加标回收率在94．7%-101．2％之间。结果表明，改进后的方法简单、快捷、干扰小．测定结果与国家标准方法相符，相对偏差均小于2．0％。

A method for the rapid determination of total phosphorus in waste water by Th（Ⅳ） prccipitation-EDTA titration. After sample of water is dissolved hy HNO3 and H2SO4 to PO4^2- and masking interfering ions in acids solution, superfluous Th（NO3）4 standard solutions is put into the waster water first. When the Th3（PO4）4 sediment is deposited, the sediment is filter and keep the filtrate is pH 2-3. Then titration is carried out by the standard solution of EDTA to end point, with the xylenol orange as the indicator. The relative standard deviation is less than 2.5% and the recovery rate of add standard is between 94.7 % and 101.2 %. The results show that the improved method is easy and fast and less interference. The results of this method accord with those obtainer by national standard method with the relative deviation less than 2.0%.