EDTA掩蔽-络合物吸附催化波极谱法测定锌电解液中钴

在丁二酮肟(DMG)和亚硝酸钠存在的氨水-氯化铵缓冲介质中,以EDTA作掩蔽剂,建立了测定锌电解液中钴的络合物吸附催化波极谱法。探究了掩蔽剂EDTA用量的选择,结果表明:所需EDTA的量与溶液中锌的含量有关,当EDTA与锌的物质的量比n_EDTA/n_Zn为1.15时为最佳选择,此时可消除锌电解液中高浓度锌及其他共存杂质金属离子对测定痕量钴的干扰。对底液酸度、氨水-氯化铵缓冲液用量、丁二酮肟乙醇溶液用量和亚硝酸钠溶液用量,以及静置时间等进行了优化。结果表明,在优化的实验条件下,钴的浓度分别在5.0×10^-11~5.0×10^-9和5.0×10^-9~3.2×10^-7mol/L范围内时与其对应的二阶导数波峰电流I_p(nA)呈良好的线性关系,相关系数分别为0.9980和为0.9997,方法检出限为2.0×10^-12mol/L。将实验方法应用于中性上清夜、锌电解新液和除钴后液等实际样品分析,测定值与国标方法GB/T 223.22—1994(亚硝基R盐分光光度法,NRS)比较,相对误差(RE)在±4.5%范围内,相对标准偏差(RSD,n=6)不大于2.7%。方法线性范围宽,对锌电解液中钴的测定具有很高选择性,适用于湿法冶金过程控制分析。

Determination of cobalt in zinc electrolyte by complex adsorptioncatalytic wave polarography with EDTA-masking

A determination method of cobalt in zinc electrolyte by complex adsorption catalytic wave polarography was established in ammonia water-ammonium chloride buffer medium in presence of dimethylglyoxime (DMG) and sodium nitrite with EDTA as masking agent. The effect of EDTA amount was investigated. The results showed that the required amount of EDTA was related to the amount of zinc in solution. The ratio of the amount of substance for EDTA and zinc (n_EDTA/n_Zn) at 1.15 was the optimal choice. At this time, the interference of high concentration zinc and other coexisting metal impurity ions in zinc electrolyte with the determination of trace cobalt could be eliminated. The acidity of base solution, the amount of ammonia water-ammonium chloride buffer solution, the amount of DMG ethanol solution, the amount of sodium nitrite solution, and the standing time were optimized. The results indicated that the concentration of cobalt (c, nmol/L) in range of 5.0×10^-11-5.0×10^-9 and 5.0×10^-9-3.2×10^-7mol/L had good linear relationship to the corresponding second derivative wave peak current (I_p, nA) under the optimized experimental conditions, respectively. The correlation coefficient was 0.9980 and 0.9997, respectively. The detection limit of method was 2.0×10^-12 mol/L. The proposed method was applied for determination of actual samples of neutral supernatant liquor, zinc electrolyte before and after removal of cobalt. The determination results were compared with those obtained by national standard method GB/T 223.22—1994 (nitroso-R-salt spectrophotometry, NRS). The relative error (RE) in range of ±4.5%, and the relative standard deviation (RSD, n=6) was not more than 2.7%. The linear range of proposed method was wide. It had high selectivity to the determination of cobalt in zinc electrolyte, and was suitable for the control analysis of hydrometallurgical processes