Positively charged nanofiltration membranes via economically mussel-substance-simulated co-deposition for textile wastewater treatment

Herein, a novel positively charged nanofiltration (NF) membrane has been facilely fabricated via a highly efficient one-step mussel-substance-simulated co-deposition of low-cost catechol and branched polyetheylenimine (PEI) onto substrates. The co-deposition behaviour, physicochemical properties and separation performances of resultant membranes can be readily tailored by varying PEI molecular weight. In particular, the catechol/PEI600 co-deposited NF membrane shows good removals toward dyes, common salts and heavy metal ions for textile wastewater treatment. Our membranes exhibit high removal efficiency toward cationic dye and metal ions due to the Donnon effect. In addition, EtOH activation process can greatly enhance the membrane permeance with a factor of 1.8-2.4 without compromising rejection. Especially, the novel membranes show stable long-term separation performance toward MgCl₂ removal, and the dye-fouled co-deposited membranes can be facilely regenerated and reused with a simple static immersion operation. The co-deposited membrane can perform well in alcohols solvents, indicating its excellent performance for practically environmentally-friendly usages. The facile strategy disclosed in our study can provide new opportunities to not only nanofiltration membrane modification but also the surface engineering of vast kinds of materials towards energy and environmental applications.