Investigation of UV/H_2O_2 Pretreatment Effects on Humic Acid Fouling on Polysulfone/Titanium Dioxide-And Polysulfone/Multiwall Carbon Nanotube-Nanocomposite Ultrafiltration Membranes

摘要

Membrane fouling is an important concern for membrane separation technology. Preparation of the feed before entering into the membrane and physicochemical modifications of membrane are both important approaches toward enhancing the permeability and separation in membrane processes. The present report combines both approaches. In terms of membrane characterization, scanning electron microscopy (SEM) images showed that the addition of titanium dioxide (TiO_2) nanoparticles and multiwall carbon nanotube (MWCNT) resulted in increased pore numbers at the top surface and more interconnected pores in the porous membrane structure. The surface hydrophilicity and porosity of the PSF/TiO_2 and PSF/MWCNT increased compared with pure PSF membranes. PSF/TiO_2 nanocomposites showed just 10% flux decline and improved 95% flux recovery ratio (FRR%). UV/H_2O_2 pretreatment changed the physicochemical properties of humic acid (HA) aggregates by reducing the super-micrometer size range (>1 μm) aggregates to a bimod-al distribution of two submicrometer size ranges <1 μm (10-100 nm and 100-1000 nm) and increased the zeta potential of HA solution due to the production of new functional groups. The oxidation pretreatment alone improved flux decline at 120 min from 21% to 80% and increased the FRR from 58% to 80% for the pure PSF. The oxidative pretreatment also improved purification for the PSF/TiO_2 nanocomposite membranes. The flux decline improved from 81% to 95% with only a slight improvement on the 94% FRR increasing to about 99% FRR. The FRR in the case of PSF/ MWCNT actually declined with the pretreatment. The hybrid process of UV/H_2O_2 pretreatment and PSF/TiO_2 nanocomposite membranes exhibited optimal permeability and antifoul-ing properties.