Hybrid membrane distillation and ion exchange process for resources recovery from mining wastewater

Abstract

This work aims to achieve a process intensification through the hybridization of direct contact membrane distillation (DCMD) and ion exchange (IX) to increase resource recovery (water, H2SO4, Copper (Cu), Nickel (Ni), and Cobalt (Co)) from a gold mining wastewater. An increase in maximum recovery rate was achieved by the DCMD in the hybrid configurations – from 34 to 52 %. Recovery of Cu, Ni and Co is best achieved by NH4OH (4 mol/L), however with considerable carryover. Conversely, selective recovery can be achieved by different eluting agents H2SO4 0.1 mol/L to recover Co (~80 %), H2SO4 1 mol/L to recover Ni (~47 %), and NH4OH 4 mol/L to recover Cu (~26 %), with a lower carryover of other ions (<14 %). Scale-up calculations showed that the Amberlyst A26 mass required for the hybrid IX (batch) is 2.4× lower than the Dowex M4195, which resulted from the exchange capacity and selectivity. Conversely, the estimated Amberlyst A26 mass required for the hybrid IX (fixed-bed) was higher due to the higher initial concentration of H₂SO₄. Lastly, CapEX ranged from 0.2 to 5.6 M US$, and OpEX from 2.61 to 11.42 US$/m3. Considering earnings with the recovered resources the hybrid fixed-bed configurations are a clear choice due to the lowest payback times (<4 years).