Sodium peroxide fusion for reliable determination of gold in ores and metallurgical samples

Abstract

A protocol based on peroxide fusion has been developed for the determination of Au in metallurgical samples and ores covering a wide range of concentrations and diverse mineralogies. The quantity of Na 2 O 2 required was minimised, while maintaining lixiviant efficacy, by the use of mixed NaOH + Na 2 O 2 fluxes. The method was shown to be applicable to the determination of coarsely-particulate gold. Fusion cakes were dissolved in hydrochloric acid and then extracted using methylisobutylketone to provide concentrations appropriate for quantification by graphite furnace atomic absorption spectroscopy and to minimise interferences from dissolved salts. The protocol was tested on a variety of certified reference materials and produced results in excellent agreement (at Au concentrations ranging from 0.05 to 47 µg g -1 ) with the traditional lead fire assay method, while avoiding the health and safety issues associated with that technique. KeywordsGold, peroxide fusion, metallurgical samples, ores Highlights 3 to 5 bullet points (maximum 85 characters, including spaces, per bullet point) Peroxide fusion GFAAS method suitable for routine commercial lab analysis developed Results comparable to Pb fire assay over wide range of mineralogy and concentration Potential for gold losses critically evaluated and found to be minimal Addition of NaOH significantly reduces amount of Na 2 O 2 required

Performance of Sample Preparation for Determination of Gold in Samples of Geological Origin

“…The availability of a more effective grinding technique to reduce sample mass needed for analysis could alleviate this problem by correspondingly reducing reagent use or by expediting the use of more benign methods of analysis viable at the gram scale such as sodium peroxide fusion (Daniel et al . ).…”

“…Gold mining service laboratories analysing hundreds or thousands of samples per day must therefore manage occupational health and safety, and waste disposal hazards of reagent use and waste generation at tonnage scale. The availability of a more effective grinding technique to reduce sample mass needed for analysis could alleviate this problem by correspondingly reducing reagent use or by expediting the use of more benign methods of analysis viable at the gram scale such as sodium peroxide fusion (Daniel et al 2017).…”