Construction of a novel Ag/AgBr/AgI@SiO2 composite aerogel with controlled pore structure: Efficient removal of tetracycline by adsorption/photocatalysis synergism under visible light irradiation

Adsorption and photocatalytic degradation are effective ways to remove pollutants from water and achieve purification effect. In order to obtain composite aerogels with high adsorption capacity and visible light photocatalytic performance, a new type of Ag/AgBr/AgI@SiO2 composite aerogels (ABIS) was prepared by in-situ synthesis and supercritical drying. It has been proved that the pore size, pore volume and specific surface area of the composite aerogels can be effectively improved by using N, N-dimethylacetamide (DMAC) as pore expanding agent. The as-prepared Ag/AgBr/AgI@SiO2 composite aerogels with large pore volume, large pore size and uniform pore network structure not only showed high adsorption capacity for tetracycline, but also exhibited high separation and migration efficiency of photo-generated carriers, thereby being capable of reducing the recombination rate of photo-generated electron-hole pairs. Especially, the composite aerogel ABIS-2-N2 with loading 0.01 mol% Ag/AgBr/AgI and adding DMAC as pore-expanding agent, showed the highest adsorption/photocatalytic degradation efficiency for antibiotic tetracycline under visible light, and meanwhile exhibited high performance of photocatalytic degradation of tetracycline and recycling stability in the range of pH= 2–10. The superoxide anion (·O2-) was proved to be the main active substance to degrade tetracycline by the active substance capturing experiment. This work provides a new effective strategy for preparing composite aerogel materials with large pore volume, large pore size and adsorption/photocatalysis synergistic action, and the as-prepared composite aerogel will have important application value in the field of water purification.