Retention of pesticides and metabolites by nanofiltration by effects of size and dipole moment

Abstract

This study is focused on the possibility of pesticide and DEA elimination by nanofiltration using NF and OPMN-K membranes. Experiments are carried out on laboratory equipment in batch circulation and applied pressures vary between 10 and 25bars. Three common pesticides (simazine, atrazine, diuron) and a chlorinated metabolite of atrazine: diethylatrazine is used as solutes, either alone or in complex solutions.For all experiments, NF shows better performance compared to OPMN-K. The most retained pesticide is atrazine and the least retained is diuron due to its higher dipole moment (high carbonyl group contribution) coupled to linear form which may also induce a decrease in its steric retention. In the case of pesticide/DEA mixtures, DEA rejection is better (up to 44%) for all pressures due to the formation of macromolecular complexes. It is also noticed that molecular weight and size, expressed by Stokes radius, are not the only parameters influencing rejection: shape of the molecule (molecular length and width) has a strong influence on rejection. The observed rejection increases when length and width increase.The nanofiltration technology seems to be a good way to treat the problem of pesticide pollution in one step process.