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

ABSTRACT

A procedure employing inductively coupled plasma optical emission spectrometry (ICP-OES) for the determination of solubilised Hg during the modelled cyanidation of Hg⁰-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 μg/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 Hg⁰ is oxidised and then solubilised in the presence of cyanide.

KEYWORDS:

• Inductively coupled plasma optical emission spectroscopy
• direct mercury analysis
• artisanal small-scale gold mining
• solvation of mercury

Disclosure statement

No potential conflict of interest was reported by the authors.