en.Wedoany.com Reported - Brazil's Nexa Recursos Minerais has successfully stabilized and improved lead and silver recovery rates at the Vazante mine in Minas Gerais by combining carboxymethyl cellulose (CMC) with a controlled sulfidation flotation process, addressing production bottlenecks caused by changes in ore characteristics. The project has been shortlisted for the 2026 Mining and Metallurgical Industry Excellence Award, organized by Minérios & Minerales magazine, which will be presented at Minascentro in Belo Horizonte from June 10 to 11, coinciding with the 17th Opex Seminar.
The Vazante processing plant was originally designed to handle specific mineral types, historically focusing on zinc concentrate production through willemite flotation, from which galena (a sulfide) was separated to obtain a lead-silver concentrate. However, as mining depth increased and the proportion of feed from the new Extremo Norte mine gradually rose, the ore began to contain significant amounts of cerussite (an oxidized lead variant). This geological change led to a sharp decline in lead and silver metallurgical recovery. Since the metal separation step is located at the beginning of the process after the pulp leaves the mill, the engineering team needed to find a rapid and effective solution without physical modifications to the plant layout or process, as there was no space for new structural installations.
Project research focused on two main hypotheses from technical literature: applying specific collectors for carbonate minerals and implementing a sulfidation route to convert the cerussite surface into a compound similar to sulfide galena. According to the project authors, preliminary tests in bench-scale mechanical flotation cells ruled out the direct use of collectors, as substances such as oleic acid and hydroxyquinoline did not show satisfactory results in improving expected performance. The methodological turning point came with sulfidation tests using sodium sulfide combined with a gangue depressant, which demonstrated potential gains consistent with the alkaline pH conditions of industrial operations.
