Developing Cu²⁺-Selective Pressure Driven Enrichment Technology Using IDA-Functionalized Membranes

Membrane-based ion recovery has gained much attention due to the growth in worldwide resource demand. Recent work with surface modified membranes has shown high ion-specific selectivity but are yet to be demonstrated in a scalable separation process. In this study, we investigated the use of surface-modified nanofiltration membranes in an ion-selective pressure driven separation process. We deposited a polymer functionalized with Cu²⁺-selective chelating groups onto a polyacrylonitrile ultrafiltration membrane through layer-by-layer deposition. The resulting membranes exhibited permselectivity of up to 30 for Cu²⁺/Mg²⁺ and 20 for Cu²⁺/Ni²⁺ with 1 mM equimolar synthetic feed in a pressure driven process. Permselectivity of up to 12.2 for Cu²⁺/Na⁺ and >2 with respect to all other ions were obtained with real mining wastewater as feed. In addition, Cu²⁺ mass percentage was increased from 0.97% in the mining waste to 32% in the second stage permeate using multi-stage separation, demonstrating practical usage of the membrane.