Sulfonation and mixing with TiO2 nanoparticles as two simultaneous solutions for reducing fouling of polysulfone loose nanofiltration membrane

The aim of this research is synthesis of high performance loose nanofiltration membranes for separation of direct dyes from textile wastewater. This involved sulfonation of polysulfone with the aim of increasing hydrophilicity and permeability; synthesis of a sulfonated polysulfone and polysulfone (SPSf/PSf) blended membrane for developing the mechanical resistance and stability of the filtration behavior; and synthesis of TiO2/SPSf/PSf nanocomposite membrane for magnifying selectivity. FTIR analysis confirmed the sulfonated groups and the TiO2 nanoparticles presence. AFM and SEM analysis proved the highest surface roughness and the smallest pore size of TiO2/SPSf/PSf nanocomposite membrane, respectively. The results of water absorption test revealed that the highest level of hydrophilicity belonged to the SPSf/PSf followed by TiO2/SPSf/PSf membrane. The nanofiltration tests showed that the SPSf/PSf membranes enjoy the highest permeability, while the TiO2/SPSf/PSf nanocomposite not only had an acceptable permeability but also presented the highest dye separation efficiency.