Fouling resistant nanofiltration membranes for the separation of oil-water emulsion and micropollutants from water

Fouling resistant nanofiltration membranes containing penta-block copolymer (PBC) as the active layer on top of polysulphone ultrafiltration membrane were prepared by self-assembly of PBC from acetone-ethanol solution followed by alkali treatment. Upon alkali treatment of the membrane, contact angle was decreased from 1150 to 930, molecular weight cut off values were increased from about 950 to 1350 Da and the pure water flux was increased from 0.5 L m(-2) h(-1) bar(-)1 to 1 L m(-2)h(-1) bar(-1). The membranes showed the rejections in the range of 22-37% for NaCI, 33-44% for MgSO4, 20-36% for MgCl2 and 45-61% for Na2SO4 when tested using 500-4000 ppm feed solution at 3.5-28 kg/cm(2) applied pressure. Rejection of organic micropollutants was decreased according to the increase in their hydrophobicity (log K-ow value) as follows: PEG-200 > benzoic acid > 2-chlorophenol > 2,4-dimethyl phenol > bisphenol-A. The composite membranes exhibited 95.5-99.5% oil rejection when tested using 500-1000 ppm engine oil in water emulsion as the feed at 3.5 kg/cm(2) applied pressure. After 8 h of permeation of oil-water emulsion, the flux recovery values were 35% for polysulphone membrane and 89-95% for composite membranes, which indicate the superior antifouling nature of the composite membranes. (C) 2015 Elsevier B.V. All rights reserved.