Removal of antibiotics and antibiotic resistance genes by self-assembled nanofiltration membranes with tailored selectivity

Antibiotics and extracellular resistance genes (eARGs) in wastewater pose a potential threat to human health and hinder wastewater reuse. In this study, we present a facile and designable approach for fabricating selective polyelectrolyte multilayer (PEM) NF membranes and evaluated their performance in antibiotics and eARGs rejection from wastewater effluent. We fabricated PEM NF membranes by layer-by-layer assembly of two strong polyelectrolytes, poly (diallyl dimethylammonium chloride) and poly (sodium styrenesulfonate). By systematic manipulation of the polyelectrolyte coating solution and deposition cycle, we obtained an asymmetric separation layer with loose bottom layers and dense top layers. The PEM membrane took full advantage of the high permeability of the loose polyelectrolyte layer and the high selectivity of the dense polyelectrolyte layer, which exhibited superior antibiotics retention while maintaining a comparable permeability to the NF270 membrane. In addition, the fabricated membranes showed excellent removal of eARGs, and membranes terminated with polyanionic electrolytes could further enhance eARG retention through electrostatic repulsion. Overall, membranes with more than four polyelectrolyte bilayers could retain >99.9% of eARG. The results show that the selective asymmetric PEM membranes provide an efficient solution for remediation of antimicrobial resistance (AMR) in wastewater.