Recovering lead from cupel waste generated in gold analysis by Pb-Fire assay

Abstract

Because of its precision and accuracy, Pb-Fire assay is the most employed method for gold analysis in geological materials. At the second stage of the method, namely cupellation, lead is oxidized to PbO which is absorbed by the cupel, leading to metallic gold as a tiny bend at the bottom of the recipient. After cupellation, cupel becomes highly contaminated with lead, making its disposal a serious risk of environmental contamination. In the present work, a leaching process for removing lead from cupel waste is proposed, which allowed for removing 96% of PbO by weight. After a precipitation step, 92.0% of lead was recovered from leachates in the form of PbSO. Lead in the solid wastes left by the extraction was above the limit established by Brazilian legislation and these were classified as non-hazardous. Finally, secondary effluents generated after the precipitation step presented lead content more than twenty times lower than that of leachates from cupel waste. Tons of cupel waste are annually generated from gold analysis by Pb-Fire assay. Thus, the proposed method can contribute to prevent the discharge of high amounts of lead into the environment. Also, recovery of lead can help to partially meet the industrial demand for lead compounds.

Sample Digestion and Combined Preconcentration Methods for the Determination of Ultra-Low Gold Levels in Rocks

“…Plessen and Erzinger [41] reported that the gold recovery did not exceed 70% when NiS-FA was used to analyze rocks. Although the gold recovery of Pb-FA is better than that of NiS-FA, the environmental pollution and harm to analysts caused by Pb discouraged its further development [42,43]. However, the bottleneck of the analysis of the low gold contents in rocks by NiS-FA consists of the high amounts of reagent blanks and low recovery efficiency of gold.…”

A new desorption method of polyurethane foam for the determination of gold and a comparative study on four desorption methods based on meta-analysis

“…The treatment methods before gold determination include dry ashing, 2–4 and wet acid digestion. Enrichment, such as precipitation, 5 ion exchange resin, 6 solvent extraction, 7–9 PUF adsorption, 10,11 extraction chromatography, 12 is followed.…”

Bismuth fire assay preconcentration and modified empirical coefficient method LA-ICP-MS for the simultaneous determination of ultra-trace Pt and Pd in geochemical samples

“…Fire assay is the application of metallurgical principles and techniques to analytical chemistry, which is an important method for precious metal elements enrichment. The target precious metals in rock, soil, metallurgy and other samples were concentrated by collectors to product high density alloy granule, conversely, the nonprecious metals and rock-forming elements reacted with solid ux to produce low density silicate or borate uids [13][14][15][16]. Thereby, the target precious metals were successfully separated from the sample matrix.…”