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 CNTOTAL were 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 AsTOTAL and CNTOTAL concentrations, with levels ranging from 0.2 to 0.3 mg L−1 for AsTOTAL and 110–1620 mg L−1 for CNTOTAL after treatment, thus exceeding environmental standards. In contrast, the RO treatment achieved removal rates of approximately 99% for AsTOTAL and CNTOTAL, resulting in concentrations <80 μg L−1 for AsTOTAL and <0.9 mg L−1 for 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.