Diagnostic leaching of galena and its oxidation products with EDTA

Many authors have used EDTA as a means of determining the extent of oxidation of flotation pulps. However, there have been few documented studies of the reaction mechanisms in the interaction of EDTA with sulphide minerals and their oxidation products. This paper examines the use of EDTA to extract lead oxidation products from galena. In the first instance, it will be demonstrated that all oxygen containing galena oxidation products (i.e. sulphate, hydroxide, oxide, and carbonate, but not polysulphide or sulphur) are rapidly solubilized in EDTA. Secondly, it is shown that EDTA does not extract lead from un-reacted galena. Continued extraction of lead with increasing conditioning time is due to continued galena oxidation, not to the extraction of lead from galena. Argon gas purging minimises this oxidation whereas the use of air or nitrogen gas purging do not. Using information gathered from these experiments, an improved EDTA extraction technique was developed and compared with other techniques used within the mining industry.