Determination of Mercury Solvation During Cyanidation of Artisanal & Small-Scale Gold Mining Tailings Via Inductively Coupled Plasma Optical Emission Spectroscopy in Comparison to Direct Mercury Analysis

A procedure employing inductively coupled plasma optical emission spectrometry (ICP-OES) for the determination of solubilised Hg during the modelled cyanidation of Hg-0-contaminated tailings from artisanal and small-scale gold mining sites was developed. Verification of Hg concentrations were achieved by comparing results using a Direct Mercury Analyser (DMA-80). The standards and the aqueous samples containing dissolved mercury were introduced into the ICP-OES directly after the addition of AuCl3 and HCl to each solution. Results indicated no retention of dissolved solids, and hence preservation of Hg within the solutions was achieved. The limit of detection for the ICP-OES was determined to be 0.005 mu g/L, and the average relative standard deviation was better than 1.1% at levels of 2.0 mg/L Hg, calculated from the peaks obtained. The addition of NaCN significantly increased the concentration of dissolved Hg and confirms that Hg-0 is oxidised and then solubilised in the presence of cyanide.