Modified titanate nanotubes incorporated polyamide layer for the fabrication offouling control thin-film nanocomposite forward osmosis membranes

Titanium dioxide nanotubes (TNTs) were prepared from titanium oxide anatase powder by hydrothermal method. The hydrophilicity of TNTs was further increased by reacting with sulphuric acid to attain sulphated TNTs (STNTs) and by reacting with [(2-amino-ethyl)-3-aminopropyl] trimethoxysilane to attain amine groups (ATNTs) on TNTs surface. The additional sintering of STNTs resulted in porous crystalline structures. The thin-film nanocomposite (TFN) membranes were synthesized by incorporation of different concentrations of modified TNTs in aqueous solution of 1,3-Phenylenediamine (MPD) during the interfacial polymerization (IP) reaction with trimesoyl chloride (TMC) on polysulfone substrate. The chemical modification of TNTs was confirmed by Fourier transform infrared (FTIR) spectroscopy, and the difference in morphology of ATNTs and STNTs was determined using transmission electron microscope (TEM). The membranes morphology and their other features were studied by Field Emission Scanning Electron Microscope (FESEM), contact angle, and Atomic Force Microscope (AFM) instruments. For the fouling study, a mixture of sodium alginate and gypsum was selected as feed solution. All of the TFN membranes produced high flux and fouling resistance ratio (FRR) values than the TFC membrane. TFN-STNT membranes exhibited moderately high flux than TFN-ATNT membranes due to additional pathways for the water transport created by the porous STNTs. However, the high FRR of TFN-ATNT membranes over STNT membranes was attributed to the interaction of-NH2 groups with acyl chloride groups of TMC at the outer interface during IP, results in smooth top surfaces.