Changing the conventional clarification method in metal sulfide precipitation by a membrane-based filtration process

The metal sulfide precipitation process is a widely studied technology used to recover metals or remove pollutants from different aqueous sources. However, the conventional clarification stage used to separate the generated precipitates cannot effectively remove them from recovered solutions. Taking this into account, the current study focuses on developing a new separation method applied in metal sulfide precipitates, based on a membrane filtration process. Different operating conditions and metal concentration in the feed solution were evaluated for the separation of copper sulfide precipitates formed from synthetic cyanide solutions in ceramic microfiltration membranes. Results showed attractive values of flux and copper recovery. Flux results ranged between 0.9 L/m2s and 1.2 L/m2s for copper concentrations above 500 mg/L, and copper recoveries resulted closer to 100% at the determined optimal operating conditions (4.5 pH, 120% NaHS stoichiometric dosage, and 2 bar feed pressure). These flux values decreased up to one order of magnitude for diluted copper concentrations, due to a change of aggregation capacity of precipitates. This study has demonstrated that the membrane filtration process can be a suitable alternative for the conventional gravitational clarification, promoting better performance results in terms of equipment capacity, metal recovery, and process safety.