TiO₂/guar gum hydrogel composite for adsorption and photodegradation of methylene blue

The development of porous adsorbent materials from renewable resources for water and wastewater treatment has received considerable interest from academia and industry. This work aims to synthesize composite hydrogel from the combination of guar gum (a neutral galactomannan polysaccharide) and TiO₂. The TiO₂-embedded guar gum hydrogel (TiO₂@GGH) was utilized to remove methylene blue through adsorption and photodegradation. The presence of TiO₂ particles in the hydrogel matrix (TiO₂@GGH) was confirmed by scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy analysis. The mercury intrusion and N₂ sorption isotherm indicate the macroporous structure of the TiO₂@GGH composite, showing the presence of pore sizes ~420 μm. The dye removal efficiency of the GGH and TiO₂@GGH was evaluated in batch mode at ambient temperature under varying pH. The effect of UV radiation on the dye removal efficiency was also assessed. The results demonstrated that the highest dye removal was recorded at pH 10, with the equilibrium condition achieved within 5 h. UV radiation was shown to enhance dye removal. The maximum adsorption capacity of TiO₂@GGH is 198.61 mg g^-1, while GGH sorbent is 188.53 mg g^-1. The results imply that UV radiation gives rise to the photodegradation effect.