Simultaneous determination of trace Cu2+, Cd2+, Ni2+ and Co2+ in zinc electrolytes by oscillopolarographic second derivative waves

Simultaneous determination of impurity metal ions in high concentration zinc solution is very important for zinc hydrometallurgy, and the purpose is to establish a method for determining the trace Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ in zinc electrolytes at the same time using the second derivative waves of single sweep oscillopolarography. Factors affecting the derivative waves of the ions were researched in a medium of dimethylglyoxime (DMG)-sodium citrate-sodium tetraborate. The results indicated that the interferences of a high concentration of Zn²⁺ and most other coexisting ions on the determination can be eliminated; when the Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ are in the ranges of 1×10^?7-3×10^?4, 6×10^?7-2×10^?4, 2×10^?8-1×10^?5 and 1×10^?8-3×10^?5 mol/L, respectively, the relationships between the peak currents of the second derivative waves and the concentrations are linear; the detection limits to determine the Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ are 8×10^?8, 2×10^?7, 6×10^?9 and 4×10^?9 mol/L, respectively. Without any sample pretreatment, the method was used to directly determine the trace Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ in actual zinc electrolytes with satisfactory results. The method is simple, sensitive and rapid.