Rejection properties of non-phenylic pesticides with nanofiltration membranes

Pesticides pollution in surface and ground water has reached a serious level of pollution and the development of pesticides removal technologies is an important subject for reducing the risk that they pose to humankind and the ecosystem. Nanofiltration (NF) membranes can be used to remove pesticides, considering that molecular weights of almost all pesticides are in the range of 200–400 Da. In a previous work, we reported that non-phenylic pesticides were rejected at a relatively lower degree by these membranes than phenylic pesticides were. In this work, we examined the rejection properties of 11 non-phenylic pesticides by reverse osmosis (RO) and NF membranes (nominal desalination degrees: 92, 60, 51, 15%). The membrane with the highest desalting degree rejected all pesticides except dichlorvos at more than 96.7%. Other membranes showed a rather less effective property. Chlorpyrifos, however, was rejected at a very high rate (>99%) by all membranes. The effects of molecular weight, molecular width, and hydrophobicity (n-octanol/water partition coefficient: log P) on the pesticide rejection were examined. The results indicate that the rejection was influenced mainly by hydrophobicity. Moreover, it was shown that all pesticides adsorbed on the membranes and the adsorption was controlled by hydrophobicity of the pesticide.