A mild one-step method to fabricate graphene oxide cross-linked with dopamine/polyethyleneimine (GO@DA/PEI) composite membranes with an ultrahigh flux for heavy metal ion removal

Heavy metal ion contamination poses a significant threat to both our environment and human health. Consequently, there is a need for proficient and environmentally friendly remediation techniques to tackle this issue. Among various strategies, membrane-based separation using graphene oxide (GO) laminate membranes has emerged as a promising solution. However, traditional GO membranes have low water permeance, poor selectivity, structural instability, and inconsistent layer spacing. In this study, we cross-linked GO with polydopamine/polyethyleneimine (DA/PEI) using a mild one-step strategy to prepare a GO@DA/PEI membrane for heavy metal ion removal and evaluated the effect of cross-linking duration on the interlayer structure, membrane properties, and heavy metal ion removal performance. The successful formation of a cross-linked network between DA/PEI and GO was proven by various characterization methods. Compared with previously reported GO-based membranes, the prepared GO@DA/PEI40 membrane exhibited excellent performance, including a peak pure water flux of 326.7 L/m2h and ion rejection of 99.6 % for Cu2+, 93.5 % for Pb2+, and 96.6 % for Zn2+, thereby overcoming the conventional trade-off" effect. The mechanism for the high flux was discussed. The cross-linking reaction between the oxygen-containing functional groups at the edges and basal planes of the GO flakes and DA/PEI were crucial to the high flux. In addition, the GO@DA/PEI40 membrane had excellent anti-fouling performance in the presence of humic acid and long-term stability under different conditions. Overall, the GO@DA/PEI membrane has good potential for heavy metal ion removal.