[DOM membrane fouling and effects on rejection behaviors of NF membranes]

This work investigated membrane fouling caused by two kinds of dissolved organic matters (DOMs), i. e., Qingcaosha (QCS) DOM and Taihu lake (TH) DOM, and the effects on the rejection behaviors of two different nanofiltration (NF) membranes, i. e., HL and ESNA1-K, using carbamazepine (CBZ) as a molecular indicator. The results showed that severe membrane fouling occurred in the presence of DOM. And the CBZ removal rate was associated with the properties and characteristics of the organic matters and the membranes. It was found that the hydrophobicity of adhered DOM cake layer was responsible for the flux decline and the influence of CBZ removal. QCS DOM increased the retention of CBZ, while TH DOM decreased the rejection rate of CBZ by both membranes tested. DOMs at medium relative molecular weight (M(r) 1 500-10 000) could adhere closely to NF membranes to form cake layer, thus changed the hydrophobicity of the membranes. DOMs at low molecular weight could enter the membrane pores reducing the M(r), which influenced the CBZ removal and resulted in membrane fouling. The experiment also showed that DOM of TH contained more hydrophobic organic matters than that of QCS, the adhesion free energy and cohesion free energy of which was more negative, and the resulting membrane fouling and membrane flux decline were more severe.