Integration of nanofiltration and reverse osmosis for metal separation and sulfuric acid recovery from gold mining effluent

Abstract This work assessed the viability of implementing sequential stages of microfiltration (MF), nanofiltration (NF) and reverse osmosis (RO) to recover sulfuric acid, separate noble metals, and produce high quality reuse water from a gold mining effluent, specifically from a pressure-oxidation process effluent. Additionally, lime demand for neutralization of the proposed treatment streams and current lime demand were compared. It was observed that the NF attained high sulfuric acid permeation, equivalent to 82%, and a substantial acid purification of approximately 77% in relation to feed solution. Moreover, the RO increased the acid content by 99% in relation to feed solution considering a recovery rate of 50%. The final RO permeate had low conductivity and reduced content of total solids and contaminants, thus showing promising potential for industrial reuse. Furthermore, the acid recovery did not led to an important loss of metals of high commercial value which were present in the raw effluent since their retention in the concentrates of the MF and NF was above 95%. The neutralization of the MF and NF concentrates allowed for a 20% reduction in lime consumption in relation current demand.