Accelerated spraying-assisted layer by layer assembly of polyethyleneimine/titania nanosheet on thin film composite membrane for reverse osmosis desalination

Abstract

Layer by layer (LbL) is a simple and versatile technique for the preparation of an ultrathin layer of composite membrane but the conventional dip-assisted LbL deposition is time consuming. In this study, an accelerated LbL assembly based on spray-on technique was successfully adopted to modify the surface of reverse osmosis (RO) thin film composite (TFC) membrane. The alternate layers of titania nanosheets (TNS) and polyethyleneimine (PEI) were formed on TFC membrane via electrostatic interaction using both spray and dip-assisted LbL deposition techniques. The membrane was investigated in terms of the changes of surface charge, hydrophilicity, roughness, ionic crosslinking and morphology. The spray-coated TFC membrane with 1 bilayer of PEI/TNS (1PEI/TNSSC-TFC) achieved the highest water permeability of 1.39 L.m−2.h−1.bar−1 compared to that of TFC membrane. It also achieved 19.42% increment in the water permeability compared to the dip-coated membrane with the same bilayer of PEI/TNS (1PEI/TNSDC-TFC) with salt rejection of 97%. 1PEI/TNSSC-TFC membrane exhibited excellent anti fouling property towards bovine serum albumin (BSA) and sodium alginate (NaAlg) with 100% of permeate recovery upon physical cleaning. This work demonstrates the feasibility of spray-coated technique in terms of the time effectiveness and the precise control of nanoparticles deposition during the surface membrane modification.