Preparation and rheology of titanium dioxide nanoparticles loaded κ-carrageenan hydrogel beads strengthened by mixed salts for multipollutant water remediation

Hydrogel beads are emerging as alternate adsorbent material for the batch or continuous column treatment of dye wastewater. Polysaccharide-based gel beads are preferred for their uniform shape and size, large specific surface area, and easy separation by filtration and subsequent reuse. In this work, we prepare and rheologically characterize UV-active κ-carrageenan/TiO<inf>2</inf> beads for the adsorption and degradation of dyes. The 3–4 mm sized nanocomposite beads are formed by the extrusion of κ-carrageenan/TiO<inf>2</inf> gel solution in salt solutions. The maximum increase in modulus was observed with the addition of 1% w/v TiO<inf>2</inf> to κ-carrageenan and subsequent crosslinking with mixed salt of KCl and CaCl<inf>2</inf>. κ-carrageenan/TiO<inf>2</inf> beads crosslinked by mixed salt of KCl and CaCl<inf>2</inf> have higher adsorption capacity, as compared to beads crosslinked with single salt of KCl. The kinetic study indicated the chemisorption of Methylene Blue on the bead surface. κ-carrageenan/TiO<inf>2</inf> beads showed higher degradation for Methylene Blue and Nile Blue A than Rhodamine B in 5 and 50 ppm each multicomponent dye systems under UV irradiation. The κ-carrageenan/TiO<inf>2</inf> beads could form a porous column for the selective adsorption of positively charged dyes from a multicomponent dye system.