Broad-spectrum rejection of emerging organic contaminants with different structure and properties from complex water matrices by chlorine-resistant Janus nanofiltration membrane

Abstract

Emerging organic contaminants (EOCs) cause global water safety crisis and pollutions, while conventional nanofiltration membranes with negative charge are insufficient to remove positively charged EOCs, and their poor chlorine resistance strongly hinders the performance. Herein, Janus membranes (JM) were tailored to reject EOCs with different structures and properties by firmly incorporating two-dimensional metal-organic frameworks (2D-MOFs) with different size and charge characteristics into chlorine-resistant and porous polyvinylidene difluoride matrix. By adjusting the ligand substitution and synthesis temperature, the pore size, charge and hydrophilicity of 2D-MOFs were controllably modulated to impart membranes with high permeability and broad-spectrum removal of positively and negatively charged EOCs (antibiotics, endocrine disrupting chemicals, per- and polyfluoroalkyl substances, organophosphate esters). JM presented superior separation performance than single-sided and state-of-the-art nanofiltration membranes owing to the electrostatic Janus structure, and porous and hydrophilic nature of 2D-MOFs. Noteworthily, JM200 membrane demonstrated exceptional water permeability (55.6 L·m-2·h-1·bar-1) and rejection of tobramycin, 3,3,5,5-Tetrabromobisphenol A, heptadecafluorononanoic acid and Tris(2-phenylphenyl) phosphate (over 99.9%). Additionally, JM200 membrane exhibits outstanding antibiotics/salt selectivity (separation factor of tobramycin/NaCl=152), anti-fouling, chlorine resistance (chlorine exposure of 400000 ppm·min) and stability, delivering superior performance than commercial NF270 membrane during long-term treatment of real surface water and municipal wastewater. This study opens a sustainable avenue for ultrafast and broad-spectrum removal of EOCs from complex water matrices with low energy and chemical consumption.