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Abstract:Hydrometallugry produces more than80%of zinc of the world recently.The technological process consists of steps as roasting leaching, purification, electrodeposition and fused cast.Generally, no less than20kinds of impurity ion exist in zinc electrolyte. When the concentration of impurity ions in the electrolyte is too high, crystallization state of the precipitated zinc,current efficiency of the process of deposition,quality of the zinc electrodeposition,and the life of electrode plate will be severely affected;and cathodic polarization appears, so it is very important to control the impurity content in zinc electrolyte.Recently, methods of impurity determination in Non-ferrous metallurgical industry are mainly two kinds of instrument analysis.Those are optical analysis and electrochemical analysis. Ultraviolet-visible spectrophotometry,high performance liquid chromatography, atomic absorption spectrometry, atomic emission spectrometry, polarography, and so on are widely used in the production practice. Polarographic method is simple, low cost, continuous detection of a variety of ion. This paper achieved continuous and rapid detection of copper(Ⅱ),cadmium(Ⅱ),cobalt(Ⅱ) in zinc electrolyte by catalytic polarography with a supporting electrolyte of composition DMG-NH3-NH4Cl-trisodium citrate-surfactant OP-10-NaNO2-Na2SO3(pH=:8.7). Copper(Ⅱ), cadmium(Ⅱ) and cobalt(Ⅱ) achieved sensitive catalytic polarographic wave in-0.31V,-0.79V,-1.10V (vs.SCE) in the supporting electrolyde respectively. Copper(Ⅱ) had good linear correlation from0.008～1.68mg/L, cadmium(Ⅱ) had good linear correlation from0.15～8.5mg/L,and cobalt(Ⅱ) had good linear correlation from0.002～1.2mg/L; When the signal-to-noise ratio is3, for copper(Ⅱ), cadmium(Ⅱ),and cobalt(Ⅱ), the method enabled the detection limit was0.0040mg/L,0.1mg/L and0.0010mg/L in the presence of a great excess of Zinc(Ⅱ) respectively. The method was applied to the determination of actual samples taked from zinc plant,with the recovery of80%～115%, the relative standard deviation of0.58%～1.6%,and the results were consistent with the ICP-AES method.The dropping mercury electrode is poisonous, and the capillary is easy to jam, but ICP-AES method has many advantanges,such as high sensitivity,easy to operate, determination of multiple elements at the same time. So the direct and simultaneous determination of copper(Ⅱ), cadmium (Ⅱ),cobalt(Ⅱ) in zinc electrolyte by ICP-AES was studied.Sample did not need pretreatment. The spectral lines with wavelengths of327.393nm,226.502nm and228.616nm were selected as the analytical lines of copper (Ⅱ), cadmium(Ⅱ), and cobalt(Ⅱ) respectively. The background interference and overlap interference were eliminated or reduced by selecting analysis and adjusting background points.The effect of the matrix was overcome by matrix matching method.The contents of copper(Ⅱ), cadmium(Ⅱ),cobalt(Ⅱ) in smelter zinc electrolyte were determined by ICP-AES in3%(V/V) HNO3medium.The method was simple,rapid and reliable.The measured value of sample was consistent with the results of polarography, with the recovery of83%～120%, the relative standard deviation of0.7%～1.3%.The method can be used for the control analysis of the contents of imprity elements in zinc electrolyte.
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