Pilot-scale reverse osmosis treatment of gold cyanidation effluent for the removal of cyanide, heavy metal(loid)s, and ionic species

Mining activities are crucial in driving economic and industrial progress, yet they present significant environmental and public health challenges. This study evaluated a conventional physicochemical treatment and a Reverse Osmosis (RO) system for highly contaminated effluents generated during gold cyanidation within the mining sector. Total organic and inorganic carbon, heavy metal(loid)s (Cu, Fe, Mn, Zn, Cr, Pb, AsTOTAL), and CNTOTALwere monitored in the conventional treatment system and permeate product of a pilot-scale RO unit equipped with a BW30 membrane during approximately five weeks of in-situ operation. The conventional treatment process substantially reduced organic carbon load (e.g., 79% removal efficiency). However, it proved ineffective in lowering AsTOTALand CNTOTALconcentrations, with levels ranging from 0.2 to 0.3 mg L−1for AsTOTALand 110–1620 mg L−1for CNTOTALafter treatment, thus exceeding environmental standards. In contrast, the RO treatment achieved removal rates of approximately 99% for AsTOTALand CNTOTAL, resulting in concentrations <80 μg L−1for AsTOTALand <0.9 mg L−1for CNTOTAL, both in compliance with regulatory requirements for effluent discharge. This analysis highlights the performance of a pilot-scale reverse osmosis unit in mitigating potentially toxic effluents in the mining industry to promote sustainable production.