Reduced graphene oxide-TiO2/sodium alginate/polyacrylamide composite hydrogel for enhanced adsorption-photocatalytic degradation of methylene blue

The discharge of dye wastewater from various industries has emerged as a critical environmental concern, necessitating the implementation of effective methods such as photocatalytic technology to mitigate organic dyes in water. Nevertheless, the poor photocatalytic activityability and low reusability of most semiconductor photocatalysts have hindered their large-scale practical application. In this paper, the reduced graphene oxide-titanium dioxide composite (rGO-TiO2) was prepared via a hydrothermal method and subsequently immobilized onto a three-dimensional structure composed of sodium alginate (SA) and polyacrylamide (PAM) through sunlight-induced polymerization and ionic cross-linking techniques, resulting in the fabrication of a novel photocatalytic composite hydrogel (rGO-TiO2/SA/PAM). The composite hydrogel was found to exhibit good photocatalytic degradation efficiency for methylene blue(MB), achieving complete removal of MB under UV light irradiation for 100 min at pH 7 when using a rGO:TiO2 ratio of 3 wt%. Additionally, the synthesis of rGO-TiO2/SA/PAM effectively harnesses solar resources through simple synthetic steps, enabling easy recovery and separation from dye wastewater (with a recovery rate of approximately after first use). In contrast, nano-TiO2 and rGO-TiO2 exhibit lower recovery rates (similar to 80%). Furthermore the material demonstrates enhanced selective adsorption-photocatalytic degradation of MB in acid-base dye mixtures under UV light irradiation.