Membrane technology applied to acid mine drainage from copper mining

The objective of this study is to evaluate the treatment of high-strength acid mine drainage (AMD) from copper mining by nanofiltration (NF) and reverse osmosis (RO) at pilot scale. The performances of two commercial spiral-wound membranes - NF99 and RO98pHt, both from Alfa Laval - were compared. The effects of pressure and feed flow on ion rejection and permeate flux were evaluated. The results showed high ion removal under optimum pressure conditions, which reached 92% for the NF99 membrane and 98% for the RO98pHt membrane. Sulfate removal reached 97% and 99% for NF99 and RO98pHt, respectively. In the case of copper, aluminum, iron and manganese, the removal percentage surpassed 95% in both membranes. Although concentration polarization limited NF performance at higher pressures, permeate fluxes observed in NF were five times greater than those obtained by RO, with only slightly lower divalent ion rejection rates, making it a promising option for the treatment of AMD.