Physicochemical stability of calcium alginate beads immobilizing TiO2 nanoparticles for removal of cationic dye under UV irradiation

Abstract

Recently, there have been considerable interests to immobilize photocatalyst in alginate beads for removing pollutants from water sources. However, the feasibility of using alginate beads in industry largely depends on its long-term stability during operation. This study investigated the physicochemical stability of alginate/titanium dioxide beads (Alg/TiO2) when exposed to UV irradiation in aqueous environment. The degradation of Alg/TiO2 beads was evident because the diameter and mass of the beads was reduced by 12% and 40%, respectively, after 120 h of irradiation. A substantial amount of TiO2 was leached into the external medium. Consequently, the removal efficiency of model cationic dye was found to reduce after every process cycle. Morphological analysis showed the formation of cavities on the surface of the Alg/TiO2 beads. Interestingly, the blank alginate beads degraded more rapidly than the Alg/TiO2 beads, confirming the UV-shielding effect of TiO2. Nevertheless, this study reveals the need to improve the UV stability of alginate-based beads before they can be considered for practical application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45002.