Determination of copper in process manganese sulfate electrolyte by differential pulse anodic stripping voltammetry

Abstract

AbstractA method is described for the reliable determination of copper in manganese sulfate electrolyte by the differential pulse anodic stripping voltammetry on a glassy carbon mercury film electrode (GCMFE). Unlike on the hanging mercury drop electrode, the high manganese sulfate electrolyte (1.3 M) proved to be an adequate medium when acidified with nitric acid for the determination of copper on a GCMFE. Under these conditions, the copper response was more pronounced due to the formation or either an intermetallic compound with manganese or a manganese oxide, which oxidizes during the stripping step. In contrast, the buffering of the electrolyte to pH ˜5 with an acetate buffer was inadequate for the copper determination. The use of the acetate buffer was also proved to be responsible for the irreproducible behavior of the copper response on mercury electrodes. Based on the preliminary acidification of the manganese sulfate electrolyte with nitric acid and the use of a 2 min deposition period, a linear concentration range between 0–100 μg/1 and a minimum detectable amount of 1 μg/1 copper above the background level present in the process plant electrolyte were accomplished. The precision of the method (relative standard deviation) ranges between 1 and 2%. Recovery studies indicated that the voltammetric method is capable of detecting 96–100% of the copper present in the high manganese sulfate electrolyte medium, providing that the sample is acidified initially with nitric acid.