Photocatalyst immobilized by hydrogel, efficient degradation and self regeneration: A review

As an advanced oxidation process, the catalytic efficiency of photocatalysis has been greatly improved because the size of catalytic materials has been reduced to nano level. However, the reduced size also makes it more difficult to reuse. In view of the fact that hydrogel composite photocatalyst can improve the practicability and economy of photocatalyst, the research and application of hydrogel composite photocatalyst deserve to be concerned. In this review, the research on hydrogel as the carrier of photocatalyst (Mainly including Titanium oxide, Carbon nitride, Metal sulfide) and the selection and preparation methods of hydrogel in recent five years is summarized. The factors affecting the photocatalytic efficiency of the composite gel system and the evaluation indexes are listed and discussed in detail. In addition, the mechanism of synergistic degradation of hydrogel composite photocatalyst was also discussed. The results showed that photocatalytic degradation and hydrogel adsorption promoted each other. Finally, the existing problems of hydrogel composite photocatalyst are summarized, and the development prospect is forecasted.