Synthesis and characterization of TiO 2 based nanomaterials and their applications in water purification

Abstract

TiO 2 nanoparticles have received great amount of research interest due to their interesting properties like photocatalysis, self-cleaning, super hydrophilicity etc. This work focuses on TiO 2 nanofibers (TNF) and nanosheets (TNS). Hydrothermal technique was used for synthesising both the nanostructures. The nanostructures were used for water purification via two modes: - nanocomposite membrane and photocatalytic hierarchical membranes. As such synthesised TiO 2 nanostructures were blend with polysulfone to form nanocomposite ultrafiltration membranes. Polysulfone (PSF) is a good polymer for membrane synthesis but its hydrophobicity results in greater fouling. The addition of hydrophilic TiO 2 nanostructures can improve the hydrophilicity and enhance the membrane performance. TNF were incorporated in PSF along with polyethylene glycol as a pore former. The novel membranes showed high flux and superior antifouling properties. Highest performance was observed at 10 wt% addition of TNF. TNS was also incorporated in PSF and the membranes were used for rejection of dyes. Best performance for congo red dye rejection was observed at 12-15 wt% addition of TNS. For rhodamine-B dye best performance was observed at 7-10 wt% addition of TNS. Apart from ultrafiltration membranes, the photocatalytic activity of the TiO 2 nanostructures were also studied and applied for water treatment. Hierarchical membranes (HM) were synthesised using these nanostructures along with modifiers like silver (Ag) & graphene oxide (GO). TNF was doped with Ag to improve their photocatalytic activity and used for synthesizing hierarchical membrane for dye degradation. The Ag-TNS membranes showed good degradation for rhodamine-B dye. TNS had shown better photocatalytic activity during preliminary studies, hence they were used extensively for making photocatalytic hierarchical membranes. TNS was modified with GO to form a composite and used for hierarchical membrane synthesis. The membranes exhibited very good dye removal capabilities. Similarly Ag was also used as a modifier for TNS and applied in hierarchical membranes. The membranes showed good congo red dye removal capacity and also exhibited potential to work under solar radiation. The capability to photo degrade under solar radiation was further explored by synthesising a floating photocatalyst by coating low density polyethylene beads with a composite film of Ag-TNS in PSF. The beads showed appreciable photo degradation of congo red dye under sun light.