Removal of emerging contaminants from secondary effluents by micellar-enhanced ultrafiltration

The removal of 11 selected emerging contaminants (ECs, acetaminophen, metoprolol, caffeine, antipyrine, sulfamethoxazole, flumequine, ketorolac, atrazine, isoproturon, 2-hydroxybiphenyl and diclofenac) by micellar-enhanced ultrafiltration (MEUF) has been investigated. Anionic sodium dodecylsulfate (SDS), non-ionic surfactants Triton X-100 (TX-100) and Tween 20 (TW-20), and cationic surfactants cetylpyridinium chloride (CPC) and cetyl trimethyl ammonium bromide (CTAB) were used. The retention coefficients of the selected compounds were determined in order to evaluate the separation efficiency of ECs from surfactant micelles. It was found that cationic surfactants were more appropriated for the removal of negatively charged and hydrophobic ECs. However, the presence of surfactant decreased the permeate flux due to the concentration polarization and membrane fouling. Among surfactants, the best results in terms of lower membrane fouling and higher retention of ECs were obtained with CPC. In addition, the effects of the MWCO of UF membranes and the water matrix on ECs and CPC removal and on membrane fouling were also evaluated. The increase of the feed CPC concentration improved the removal of ECs, although the permeate flux decreased. The removal of ECs and CPC was not affected by trans-membrane pressure. According to these results, solubilisation of ECs in the micelles and retention of the micelles by the membrane govern the overall retention process.