摘要
湿法炼锌流程中钴渣浸出液中含有高浓度的Fe~(2+)和Mn~(2+),用分光光度法测定Co~(2+)和Ni~(2+)时,Fe~(2+)-EDTA会严重干扰Co~(2+)和Ni~(2+)的测定;在用光度滴定法测定Zn~(2+)和Co~(2+)合量时,Ni~(2+)对二甲酚橙指示剂具有封闭作用,Mn~(2+)亦与EDTA螯合,导致滴定结果偏高。为消除Fe~(2+)和Mn~(2+)对Zn~(2+)、Co~(2+)和Ni~(2+)测定的干扰,实验进行氧化分离Fe~(2+)和Mn~(2+)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Co~(2+)、Ni~(2+)。在波长466nm处,Co~(2+)的线性范围为50~500mg/L时与吸光度呈线性,相关系数R2为0.999 2;在384nm处,Ni~(2+)的线性范围为50~500mg/L时与吸光度呈线性,相关系数R2为0.999 8。根据分光光度法测出Ni~(2+)物质的量,加入1.1倍的丁二酮肟以除去Ni~(2+),用二甲酚橙为指示剂,EDTA鳌合-光度滴定法测定Zn~(2+)、Co~(2+)合量,扣减Co~(2+)含量得出Zn~(2+)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Co~(2+)和Ni~(2+),光度滴定法测定Zn~(2+)、Co~(2+)合量,Zn~(2+)、Co~(2+)和Ni~(2+)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%。
The cobalt residue leaching solution in zinc hydrometallurgy contained high concentrations of Fe~(2+)and Mn~(2+).During the determination of Co~(2+)and Ni~(2+)by spectrophotometry,Fe~(2+)-EDTA had serious interference.On the other hand,when the total content of Zn~(2+)and Co~(2+)was determined by photometric titration,Ni~(2+)had blocking effect of xylenol orange indicator and Mn~(2+)could chelate with EDTA,resulting in higher titration results.In order to eliminate the interference of Fe~(2+)and Mn~(2+)on the determination of Zn~(2+),Co~(2+)and Ni~(2+),the pretreatment of Fe~(2+)and Mn~(2+)was conducted by oxidization separation in experiments.Co~(2+)and Ni~(2+)were determined by spectrophotometry using EDTA as coloring reagent in NaAc/HAc buffer solution.The concentration of Co~(2+)in range of 50-500 mg/L was linear to the absorbance at 466 nm and the correlation coefficient was R2=0.999 2.The concentration of Ni~(2+)in range of 50-500 mg/L was linear to the absorbance at 384 nm and the correlation coefficient was R2=0.999 8.The molar amount of Ni~(2+)was determined by spectrophotometry.Then Ni~(2+)was removed by adding 1.1 times of dimethylglyoxime.The total content of Zn~(2+)and Co~(2+)was determined by EDTA chelation-photometric titration using xylenol orange as indicator.The content of Zn~(2+)was calculated by deducting the content of Co~(2+).Four actual samples of cobalt residue leaching solution in zinc hydrometallurgy were selected.The content of Co~(2+)and Ni~(2+)was determined by spectrophotometry according to the experimental method.The total content of Zn~(2+)and Co~(2+)was determined by photometric titration.The relative standard deviations(RSD,n=6)of Zn~(2+),Co~(2+)and Ni~(2+)were all less than 0.70%.The spiked recoveries were 99.59%-100.41%,99.69%-100.64%and 99.92%-100.08%,respectively.
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