Polysulfone ultrafiltration membranes modified with carbon-coated alumina supported ni- TiO₂ nanoparticles for water treatment: Synthesis, characterization and application

This paper reports on the synthesis and characterisation of polysulfone (PSf) ultrafiltration (UF) membranes modified with carbon coated alumina Ni-doped titanium dioxide (CCA/ Ni-TiO₂) nanoparticles. The syntheses of the membranes was carried out using the phase inversion process. The permeate flux of the membrane modified with 0.25% CCA/Ni-TiO₂ nanoparticles (213.5±6.40 L.m^-2.h^-1) was found to be higher than that of the unmodified membrane (130.95±4.50 L.m^-2.h^-1) at 13.8 bar. The membrane modified with 0.50% CCA/Ni- TiO₂ nanoparticles had the lowest permeate flux at 105.18±4.52 L.m^-2.h^-1. The improved water permeability was brought about by the hydrophilicity resulting from introduction of the hydroxyl groups of the nanoparticles. At 13.8 bar, the NaCl salt rejection properties of the mixed matrix membranes were relatively higher (31.38±1.23%) for the 0.25% PSf/CCA/ Ni-TiO₂ membranes compared to that of the unmodified PSf membrane (12.76±1.10%). Similar observations were made for the Cr³⁺ heavy metal rejection, which ranged between 56.27±2.54% and 60.48±2.52% for the modified membranes. These results have demonstrated the role the electrostatic effects of the nanoparticles play in the rejection mechanism of the modified membranes when compared to the unmodified membranes. Unmodified membranes were found to reject 28.32±1.65% of Cr³⁺ heavy metals at the same pressure. Over a period of 180 minutes, the membranes were found to be more photocatalytically active towards bromophenol blue, and a maximum photodegradation efficiency of 81% was achieved compared to only 50.5% for methyl orange. The photo-degradation process for both dyes followed a pseudo-first-order reaction rate.