The performance of a thin-film composite (TFC-ES) polyamide forward osmosis (FO) membrane in rejecting pharmaceuticals (PhACs) was investigated and compared with two asymmetric cellulose triacetate (CTA-ES and CTA-NW) membranes. Results showed that the TFC-ES membrane had a higher water permeability and salt rejection ability, but a poorer performance in rejecting the selected 21 PhACs (as a sum) than both CTA membranes. The TFC-ES membrane exhibited a better rejection of the negatively charged PhACs than the positively charged and neutral PhACs as theoretically predicted based on membrane surface charge. That the permeability coefficient values for all the positively charged PhACs determined in the FO mode were larger than that in the reverse osmosis mode was speculated to result from the impact of reverse draw solute diffusion on FO rejection of those PhACs. “Ion exchange” might be the mechanism, which could make additional contribution to the transport of positively charged PhACs and result in lower rejections than as expected. In addition to steric exclusion and electrostatic effect, the PhAC-membrane interactions could also play an important role in the transport of PhACs and affect the rejection by the FO membranes.
All Science Journal Classification (ASJC) codes
- Water Science and Technology
- Ocean Engineering