Removal of phenyl-urea herbicides in ultrapure water by ultrafiltration and nanofiltration processes

Membrane filtration of four phenyl-urea herbicides (linuron, diuron, chlortoluron, and isoproturon) dissolved in ultrapure water was studied in a laboratory cross-flow device in batch concentration mode (with recycling of the retentate stream). Three UF (MWCO of 20 000, 5000 and 2000 Da) and three NF (MWCO of 150-300 Da) membranes were used. The influence of the main operating conditions (transmembrane pressure, tangential velocity, temperature, pH, and MWCO of the membranes) on the steady-state permeate fluxes and the retention factors of the phenyl-ureas was evaluated. The herbicide mass adsorbed onto the membranes was also determined, and the contribution of the fouling resistance to the total resistance to permeate flux was much lower than the inherent resistance of the clean membranes.