Micro-patterned cellulose triacetate membranes for forward osmosis: Synthesis, performance and anti-fouling behavior

Most cellulose triacetate (CTA)-based studies for forward osmosis (FO) have greatly focused on achieving asymmetric membranes with a highly porous sublayer along with a dense selective layer. Such membranes can achieve better fluxes due to improved mass transfer and reduced internal concentration polarization. In this work, patterning of the CTA-membranes via modification of the conventional non-solvent induced phase inversion is explored as an alternative route to increase FO water flux without reducing salt selectivity. The modified way of applying the non-solvent in this method increased the membrane bulk porosity from ~17 % to ~50 %. Such high porosity and reduced tortuosity of the patterned membrane can reduce the internal concentration polarization by back-transport and reduced accumulation of salt and other solutes in the porous support. During FO, the patterned CTA membrane showed a water flux of 30 L m−2 h−1 and reverse salt flux of 25 g m−2 h−1, thanks to the increased effective membrane area, low water transport resistance, and high porosity of the membrane support. The patterned CTA-membranes may have potential in FO for applications with larger draw solutes due to the slightly larger pores on the membrane surface following the non-solvent spraying. Alternatively, some phase inversion parameters can still be further tuned to lower the salt passage. •Simultaneous non-solvent spraying and patterning as an alternative route for improved FO performance.•CTA FO membranes with highly porous sub-layer, dense selective layer and increased membrane contact area.•Proportional increase in water flux with increased surface area and reduced reverse salt flux.•Triangular patterned membrane showed optimum water flux, reverse salt flux and reduced fouling properties.