Enhanced resource recovery from wastewater using electrochemical-osmotic system with nanofiltration membranes

Abstract

Mining diverse resources from electroplating wastewater are critical for maximizing wastewater economic value and minimizing adverse environmental impacts. We have demonstrated an autonomous electrochemical-osmotic system (EOS), which can simultaneously recover copper metals, water, and electric energy from electroplating wastewater. In this study, we enhanced water production, electricity generation, and metal recovery of the EOS using polyelectrolyte multilayer nanofiltration (PMNF) membranes instead of the forward osmosis membranes. The PMNF membrane is fabricated by alternately depositing two oppositely charged polymers, poly(diallyldimethylammonium chloride) (PDADMAC, (+)) and poly(sodium 4-styrenesulfonate) (PSS, (−)), on the nanofiltration (NF) membrane substrate. Results suggested that the water/salt selectivity of the PMNF membrane increase to 25.1 L mol−1 with the increase of the number of the polyelectrolyte deposited layers to 6.0. The EOS assembled with a 1.5-layer PMNF membrane achieved a water production rate of 6.06 L m−2h−1 and a maximum power density of 1.18 mW cm−2 by treating synthetic electroplating wastewater, 2.63 and 1.21 times higher than conventional EOS (i.e., FO membrane), respectively. Further, we clarified that the PMNF-EOS effectively inhibited the forward transport of various metal cations (e.g., Cu2+, Cr6+, Zn2+, and Ni2+) while also extracting freshwater, generating power, and recovering copper from electroplating wastewater. Our study provided a new avenue for developing a high-performance EOS to reclaim multiple resources from electroplating wastewater.