Comparison of the removal of hydrophobic trace organic contaminants by forward osmosis and reverse osmosis

► The mean effective pore size of the FO membrane was calculated to be 0.74 nm. ► Filtration of hydrophobic trace organics in FO mode differed from that in RO mode. ► Adsorption was lower and rejection was higher in FO mode than in RO mode. ► This difference was attributed to the retarded forward diffusion (RFD) phenomenon. ► The RFD effect was not observed when the reverse salt flux was negligible.