Fe3+-citric acid/sodium alginate hydrogel: A photo-responsive platform for rapid water purification.

As water pollution in human society becomes more and more serious, the demand for materials that can be used for wastewater treatment is increasing. Here, we reported a sodium alginate-based hydrogel (Fe3+-CA/SA hydrogel) that can efficiently photocatalyze the degradation of malachite green. The Fe3+-CA/SA hydrogel is composed of sodium alginate, citric acid, and Fe3+. The hydrogel has multi-leveled pore structure and photochromic ability. Benefiting from the unique microstructure and positive feedback chemical reaction process, the hydrogel has high photocatalytic efficiency. Under 365 nm UV light irradiation, the hydrogel can degrade around 95% of malachite green (20 mg/L) in about 4 min, and there is no need to add H2O2 in the degradation process. The work helps to expand the application of sodium alginate-based hydrogels in the field of water treatment. It also has exploratory significance for the principle of photocatalytic degradation of malachite green.