Electroanalytical determination of soluble Mn(II) species at high concentration levels

Glassy carbon electrodes have been successfully employed for the determination, by differential pulse voltammetry, of Mn(II) ions dissolved in aqueous solutions. In particular, a simple and fast procedure also suitable for on-line or at-line process control has been developed. Statistical analysis of the results obtained reveals that the procedure can be adopted in the range 0.59-57.30 mM Mn(II). The electrochemical responses are repeatable and reproducible. Repeatability is testified by the lack of variation of peak current values calculated from 20 subsequent scans carried out at the maximum explored concentration (relative standard deviation <1%). Reproducibility of the responses is supported by the data from the responses on three different electrodes. The proposed procedure does not require any pre-concentration of Mn species at the electrode surface or de-aeration of the solution. By adopting the developed procedure for the analysis, the GC electrode demonstrates to be suitable also for application in real matrices, namely solutions from spent battery recycling; in particular the results from the present electrochemical method are not significantly different from those obtained through inductively plasma coupled mass spectrometry. Interference from other metal species, such as Zn(II) and Fe(III), is negligible. This result is particularly meaningful, since the experimental conditions chosen, implying particularly high concentrations of heavy metals, are representative of those adopted in recovery and recycle processes of Mn species from batteries.