Novel thin-film composite membrane with polydopamine-modified polyethylene support and tannic acid-Fe3+ interlayer for forward osmosis applications

Polyethylene (PE) has recently gained attention as an advantageous support material in forward osmosis (FO) owing to its low structural parameters. A novel thin-film composite (TFC) membrane for FO was fabricated by introducing a tannic acid (TA)-Fe3+ interlayer on a polydopamine (PDA)-modified PE support via interfacial polymerization. The TA-Fe3+ interlayer influenced the diffusion of m-phenylenediamine, causing a unique wormlike morphology of the polyamide (PA) layer, distinct from the traditional ridge and valley morphology. Wormlike structures provided more permeation sites and improved the water flux (71.2 L.m(-2).h(-1)). Furthermore, the TA-Fe3+ interlayer prevented some salt molecules from passing through and resulted in a low specific salt flux (0.03 g.L-1). The TA-Fe3+ interlayer was the key to overcoming the trade-off between permeability and selectivity. It functioned as a bridge connecting the PA layer and the PDA-modified PE support through chemical bonding, and the adhesion strength between PA layer and PDA-modified PE support was enhanced. This resulted in the excellent stability of the obtained TFC membrane. This study presents a new method for the design of a TFC membrane with excellent perm-selectivity and manipulatable morphologies of the PA layer for FO applications.

Automated summary

A novel thin-film composite (TFC) membrane for forward osmosis (FO) was fabricated by introducing a tannic acid (TA)-Fe3+ interlayer on a polydopamine (PDA)-modified polyethylene (PE) support. The unique wormlike morphology of the polyamide (PA) layer in the membrane increased water flux and reduced salt flux, overcoming the trade-off between permeability and selectivity. The TA-Fe3+ interlayer enhanced the adhesion strength between PA layer and PDA-modified PE support, resulting in excellent stability of the TFC membrane for FO applications.