Green synthesis and environmental applications of alginate/polyacrylamide/titanium dioxide composite hydrogel

Abstract A multifunctional sodium alginate/polyacrylamide/titanium dioxide (SA/PAM/TiO 2 ) double network composite hydrogel was successfully prepared by sunlight‐induced polymerization and ionic cross‐linking method and the relationship between its structure and properties was studied. During the polymerization process, TiO 2 is used as an initiator to promote the polymerization and is homogeneously immobilized on the three‐dimensional double network hydrogel matrix as the active component of photo‐catalysis. The dual network structure and highly hydrophilic functional groups in the structure improves the adsorption capacities of the hydrogel and photocatalytic performance of the catalyst by avoiding the aggregation of TiO 2 . The influences of different factors, such as the amount of cross‐linker, monomer ratio, titanium dioxide content, and exposure time, on the swelling properties of the hydrogel during the reaction process were investigated. The effects of titanium dioxide content, pH value, and initial concentration of methyl orange solution on the adsorption properties and photocatalytic performance of the hydrogel were also examined. In addition, the environmental applications of the material as a reusable adsorbent and an effective photo‐catalyst for the treatment of dyes were explored. The hydrogel possesses excellent mechanical properties and stability and was recycled for 10 times without any significant decrease in photocatalytic efficiency.