Photo-induced graft polymerization of N-isopropyl acrylamide on thin film composite membrane: Produced water treatment and antifouling properties

Thin film composite (TFC) nanofiltration membranes are widely used for waste water treatments. However, membrane fouling constitutes a major obstacle for the applications of TFC technology for the treatment of waste water. Fouling is caused by undesired interactions between colloids (e.g. oil droplets in water) with the membrane active surface. The consequence is a sharp decline in permeate flux and changing permeate quality with operation time, which has detrimental effects on the efficiency and economics of the membrane process. Membrane fouling could be controlled by altering the surface chemistry of membrane. Changing the membrane surface chemistry by surface modification of temperature responsive polymer is an attractive approach to reduce membrane fouling. In this study, we made an approach to modify the membrane surface with temperature responsive polymer such as poly(N-isopropyl acrylamide) poly(NIPAM) by photo-induced graft polymerization method. Membrane surfaces were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy and attenuated total reflection-Fourier transform infrared analysis. Changes in surface chemistry and morphology confirmed the grafting of poly(NIPAM). Hydrophilicity of the grafted membrane has been improved significantly which was determined by contact angle measurements. Furthermore, grafted membranes shows temperature responsive property which was characterized by lower critical solution temperature of poly(NIPAM) at temperature similar to 30 degrees C. Grafted membrane was used for the treatment of waste water obtained from coal bed methane gas exploration which is known as produced or co-produced water. Permeate flux through the grafted membrane has been decreased due the blockage of surface/pores. However, grafted membrane gave better results in terms of separation such as salt rejection. Initial salt rejection of grafted membrane is 48.04% as compared to the 7.2% for un-grafted membrane. FESEM revealed used grafted membranes are capable to release the foulants after lukewarm (similar to 40 degrees C) water wash. (C) 2012 Elsevier B.V. All rights reserved.