Modification of ultrafiltration polymeric membranes with dispersed oxide nanoparticles

Abstract

Organic-inorganic membranes containing the nanoparticles of hydrated zirconium dioxide and BaFe12O19 magnetic nanoparticles were prepared. The nanoparticles were inserted into polymer matrices. Ultrafiltration membranes were used as a polymer substrate. These materials consist of macroporous layer (non-woven polyester) and ultrathin active layer (polysulfone or polyacrylonitrile). Morphology of the membranes was investigated using scanning electron microscopy. It was established that inorganic nanoparticles form aggregates, a size of which is up to 20 nm in active layer and up to 2 m in macroporous fibrous support. Larger aggregates are formed in the absence of a magnetic constituent (up to 5 m). Fractal analysis showed the diffusion-limited aggregation model of particle formation. The inorganic particles form a «secondary active layer» inside the polymer pores: this layer determines water flux and rejection ability of the membrane. A thinner «secondary active layer» is formed in the polymer matrix containing smaller pores. The prepared membranes were tested for filtration of sugar beet juice. The modification was shown to improve the ability of the membranes to reject proteins. Due to smaller particle size, the membrane containing BaFe12O19 shows the liquid flux of 4.310–7–5.710–7 m3m–2s –1 at 2 bar and the rejection towards vegetable protein of 55–87%. Regarding the membranes that do not include magnetic nanoparticles, these values are 3.810–7–5.510–7 m3m–2s –1 and 38–77%, respectively.