Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges in wastewater treatment. For traditional photocatalytic materials, there are always some limitations. For example, their photocatalytic performance is limited due to their high band gap (UV range) and recombination time of photogenerated electron-hole pairs [1]. Additionally, photocatalytic materials face the challenges of secondary pollution to the environment and poor recycling performance. Hydrogel photocatalysts has been of high removal efficiency of water pollutants due to its adsorption capacities and good environmental compatibility. Hydrogels are macromolecular hydrophilic polymetric gels with cross-linked 3D structures that can easily entrap water molecules in their pores or interstitial spaces to swell up while remaining insoluble. Hydrogels exhibit high structural flexibility, chemical stability, elasticity and permeability, enhancing their water absorption capability. In this review, we will mainly focus on the photocatalytic degradation properties of sodium alginate (SA) hydrogel and explore its further application in wastewater treatment (dye degradation). Also, we compare the metal-ion-doped graphene hydrogel (MGH) with SA hydrogel in efficiency, conditions control and further prospects etc.
