EDTA滴定法测定氧压浸出溶液中锌

在锌冶炼过程的氧压浸出溶液中由于铜、铁、锰等杂质元素的存在,在使用EDTA络合滴定锌时终点变色不明显,结果误差大,不符合生产要求。采用硝酸消解试样,加入氨水、氯化铵、氟化钾沉淀分离铁、铅等元素,加入过硫酸铵使锰以二氧化锰析出;在pH 5.5~6.0的乙酸-乙酸钠缓冲溶液中以二甲酚橙为指示剂,铜(II)用硫脲掩蔽、铝用氟化钠掩蔽,滴定前加入抗坏血酸解除铁(III)对指示剂的封闭,用EDTA标准溶液滴定锌,终点明显,从而建立了使用EDTA滴定法测定氧压浸出溶液中锌的方法。按照实验方法测定氧压浸出溶液中锌,结果的相对标准偏差(RSD,n=9)为0.43%~1.3%;加标回收率为99%~102%;实验方法用于测定6个氧压浸出溶液中锌,测定值与参考值相吻合。

Determination of zinc in oxygen pressure leaching solution by EDTA titration

Some impurity elements existed in oxygen pressure leaching solution in zinc smelting process such as copper, iron and manganese. As a result, the color change of endpoint during EDTA complexometric titration was not obvious. The result error was great, which could not meet the production requirements. The sample was digested with nitric acid. The ammonia water, ammonium chloride and potassium fluoride was added for the precipitation and separation of iron and lead. The ammonium persulfate was added to precipitate manganese in the form of manganese dioxide. In acetic acid-sodium acetate buffer solution at pH 5.5-6.0, copper (II) and aluminum was masked with thiourea and sodium fluoride, respectively. The ascorbic acid was added before titration to release the closure of iron (III) to the indictor (i.e., xylenol orange). The content of zinc was titrated using EDTA standard solution. The color change of endpoint was obvious. Consequently, the determination method of zinc in oxygen pressure leaching solution by EDTA titration was established. The content of zinc in oxygen pressure leaching solution was determined according to the experimental method. The relative standard deviations (RSD, n=9) of found results were between 0.43% and 1.3%. The spiked recoveries were between 99% and 102%. The proposed method was applied for the determination of zinc in six samples of oxygen pressure leaching solution, and the found results were consistent with the reference values.