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

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 (similar to 80 %), H2SO4 1 mol/L to recover Ni (similar to 47 %), and NH4OH 4 mol/L to recover Cu (similar to 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 2.4x 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$, and OpEX from 2.61 to 11.42 US$/m(3). Considering earnings with the recovered resources the hybrid fixed-bed configurations are a clear choice due to the lowest payback times (<4 years).