Simultaneous determination of trace amounts of nickel, cobalt, and zinc in the wastewater of a galvanic workshop by using adsorptive cathodic stripping voltammetry

Electroplating of Ni, Co, and Zn is widely used in the industry, because coating of tools with these materials can improve mechanical and chemical properties such as hardness, toughness, and corrosion resistively. Ni, Co, and Zn are among toxic metals of significance for environmental surveillance. Therefore, determination of these elements in wastewater is very important. This paper reports the use of an adsorptive cathodic stripping voltammetric technique for the simultaneous determination of Ni(II), Co(II), and Zn(II) with dimethylglyoxime (DMG) as a chelating agent. Voltammograms of Ni(II), Co(II), and Zn(II) initially contained three C peaks corresponding to these metals. However, the peaks overlapped. Therefore, the effect of organic solvents was studied, and the results showed that the use of a suitable ratio of ethanol-water (I : 5) solvent and pH provided peaks that were distinctly separated. The metals can be quantified at concentrations above 0.03 (Ni), 0.02 (Co), and 0.1 mu g/mL (Zn). The RSD (%) at concentration levels of 0.10 tg/ml Ni(II), 0.10 mu g/mL Co(II), and 0.30 mu g/mL Zn(II) is 2.3, 2.0, and 3.3%, respectively. The influence of pH, DMG concentration, scan rate, accumulations time, and potential was investigated. The method was satisfactorily used for determination of the metals under study in water and wastewater.