分光光度法和光度滴定法联合测定湿法炼锌流程中钴渣浸出液中锌钴镍

湿法炼锌流程中钴渣浸出液中含有高浓度的Fe²⁺和Mn²⁺,用分光光度法测定Co²⁺和Ni²⁺时,Fe²⁺-EDTA会严重干扰Co²⁺和Ni²⁺的测定;在用光度滴定法测定Zn²⁺和Co²⁺合量时,Ni²⁺对二甲酚橙指示剂具有封闭作用,Mn²⁺亦与EDTA螯合,导致滴定结果偏高。为消除Fe²⁺和Mn²⁺对Zn²⁺、Co²⁺和Ni²⁺测定的干扰,实验进行氧化分离Fe²⁺和Mn²⁺预处理,在NaAc/Hac缓冲体系下,以EDTA作显色剂用分光光度法测定Co²⁺、Ni²⁺。在波长466nm处,Co²⁺的线性范围为50~500mg/L时与吸光度呈线性,相关系数R²为0.9992;在384nm处,Ni²⁺的线性范围为50~500mg/L时与吸光度呈线性,相关系数R²为0.9998。根据分光光度法测出Ni²⁺物质的量,加入1.1倍的丁二酮肟以除去Ni²⁺,用二甲酚橙为指示剂,EDTA鳌合-光度滴定法测定Zn²⁺、Co²⁺合量,扣减Co²⁺含量得出Zn²⁺含量。选取4个锌湿法炼锌流程中钴渣浸出液实际样品,按照实验方法中的分光光度法测定Co²⁺和Ni²⁺,光度滴定法测定Zn²⁺、Co²⁺合量,Zn²⁺、Co²⁺和Ni²⁺测定结果的相对标准偏差(RSD,n=6)均不大于0.70%,加标回收率分别为99.59%~100.41%、99.69%~100.64%、99.92%~100.08%。

Determination of zinc,cobalt and nickel in cobalt residueleaching solution in zinc hydrometallurgy byspectrophotometry and photometric titration

The cobalt residue leaching solution in zinc hydrometallurgy contained high concentrations of Fe²⁺ and Mn²⁺. During the determination of Co²⁺ and Ni²⁺ by spectrophotometry, Fe²⁺-EDTA had serious interference. On the other hand, when the total content of Zn²⁺ and Co²⁺ was determined by photometric titration, Ni²⁺ had blocking effect of xylenol orange indicator and Mn²⁺ could chelate with EDTA ,resulting in higher titration results. In order to eliminate the interference of Fe²⁺ and Mn²⁺ on the determination of Zn²⁺, Co²⁺ and Ni²⁺, the pretreatment of Fe²⁺ and Mn²⁺ was conducted by oxidization separation in experiments. Co²⁺ and Ni²⁺ were determined by spectrophotometry using EDTA as coloring reagent in NaAc/HAc buffer solution. The concentration of Co²⁺ in range of 50-500mg/L was linear to the absorbance at 466nm and the correlation coefficient was R²=0.9992. The concentration of Ni²⁺ in range of 50-500mg/L was linear to the absorbance at 384nm and the correlation coefficient was R²=0.9998. The molar amount of Ni²⁺ was determined by spectrophotometry. Then Ni²⁺ was removed by adding 1.1 times of dimethylglyoxime. The total content of Zn²⁺ and Co²⁺ was determined by EDTA chelation-photometric titration using xylenol orange as indicator. The content of Zn²⁺ was calculated by deducting the content of Co²⁺. Four actual samples of cobalt residue leaching solution in zinc hydrometallurgy were selected. The content of Co²⁺ and Ni²⁺ was determined by spectrophotometry according to the experimental method. The total content of Zn²⁺ and Co²⁺ was determined by photometric titration. The relative standard deviations (RSD, n=6) of Zn²⁺, Co²⁺ and Ni²⁺ were all less than 0.70%. The spiked recoveries were 99.59%-100.41%, 99.69%-100.64% and 99.92%-100.08%, respectively.