Fabrication of flat-sheet TFC FO membranes

The preparation of the SPSU/PVC substrates was based on the NIPS process. The casting solution compositions are provided in Table 1. PVC and SPSU were dissolved in NMP and continuously stirred at 60 °C for 24 h to obtain a homogeneous and transparent solution. After degassing at room temperature for 24 h, the casting solution was cast on a pre-cleaned glass plate using a 150 μm stainless-steel casting knife. After evaporation in a fume hood for 30 s, the as-cast substrates with the glass plate were immersed into a deionized (DI) water coagulation bath at the ambient temperature to initiate the phase inversion. Afterwards, the obtained substrates were transferred into a flowing DI water bath for 48 h to remove residual solvent before further use.

Composition of the casting solutions for the preparation of the blended substrates.

The polyamide (PA) active layer was prepared with MPD and TMC monomers via an interfacial polymerization (IP) process on the surface of a neat PVC or SPSU/PVC substrate. First, the prepared substrate was immersed in an aqueous solution of 2.0 wt.% for 120 s. The excess MPD solution was removed by pure compressed nitrogen gas for 2 min. Then, a 0.1 wt.% n-hexane solution of TMC was gently poured onto the MPD-soaked substrate surface to form the PA layer for 60 s. After the n-hexane solution was drained off, the nascent TFC membrane was air-cured for 5 min. The resultant TFC membrane was rinsed with DI water to remove the residual monomers and then stored in DI water before characterization and performance testing. These membranes are denoted as TFC0, TFC0.5, TFC1, TFC2.5, TFC5, and TFC10 according to the label names of the substrates.