Abstract

The aim of this work was to develop anti-biofouling thin-film composite reverses osmosis membranes (TFC-RO) by incorporating TiO2 nanoparticles. Polyamide membrane was obtained by interfacial polymerization process from the aqueous phase of m-phenylenediamine (MPD) and the organic phase of trimesoyl chloride (TMC) on a porous polysulfone support (PSL). TiO2 nanoparticles with different size of particles were prepared by solvothermal method (TiO2-1 and TiO2-2, 6 nm and 20 nm respectively), and a commercial nanoparticles (Sigma Aldrich, 21 nm) was also used. These nanoparticles were homogeneously dispersed in MPD to prepare nanoparticles entrapped in polyamide membrane ((PA-TiO2)/PSL). Membranes were characterized by XRD, FTIR, FE-SEM, SEM-EDX, AFM and Contact Angle. Biofouling test was realized by the colony forming unit method (CFU) using E. Coli bacteria. This test was performance under dark and Visible/UV light to evaluate possible photocatalytic effect of TiO2. Adhesion of the bacteria on the membrane was checked by epifluorescence microscopy using fluorescent stain (Live/dead backlight bacterial viability). No changes in the XRD pattern of TiO2 on modified membranes were observed indicating that no crystal-phase transitions occurred during the incorporation of the nanoparticles. The FTIR data confirmed the formation of polyamide layer when TiO2 nanoparticles is incorporated. FE-SEM and EDX analysis evidence that nanoparticles were embedded in the polyamide matrix of the membrane. The addition of TiO2 causes decrease of contact angle in contrast with the PA/PS membrane, except for TiO2-1. It indicates that the addition of TiO2 (TiO2-2 and TiO2-C) enhances the hydrophilicity of membrane. AFM image shows that (PA+TiO2-2)/PSL present a surface slightly less roughness with respect to unmodified membrane. The number of adhered bacteria on the modified membranes decreased significantly with respect to the pristine membrane showing an excellent anti-adhesion capacity. This effect can be attributed at the enhancement in the hydrophilicity of modified membrane and their low surface roughnesses. Similar anti-adhesion percentage under dark and Visible/UV light were observed. It indicate a negligible photocatalitic effect on membranes surface.