A study was conducted on the removal and adsorption of diuron through a 200 Da nanofiltration (NF) membrane. The effects of ionic environment (0.002, 0.02 and 0.2 M of NaCl, CaCl2 center dot 2H(2)O and MgCl2 center dot 6H(2)O solutions), and operating pressure (5 and 25 bar), on the removal and adsorption of diuron, were investigated. There was a gradual increase in the removal efficiency with an increase in ionic strength. However, a better removal performance of NF membrane was achieved with the presence of intermediate ionic strength (0.02 M of NaCl). The presence of the highest ionic strength did not exhibit the highest removal efficiency for diuron. Moreover, ionic strength had a much more significant influence on the removal of diuron at a lower operating pressure (5 bar). The adsorption results indicated that there was a shielding effect of ionic strength on the adsorption of diuron, which was stronger at 5 bar. In contrast, the removal of diuron decreased significantly as the concentration of divalent cations increased at 25 bar. The experimental results also showed that the size exclusion mechanism seemed to be significant with the presence of electrolyte for the removal of diuron through the NF membrane. (C) 2010 Elsevier B.V. All rights reserved.