Highly efficient and stable Ag-g-C3N4/AC photocatalyst for photocatalytic degradation, Cr(VI) reduction and bacteriostasis under visible light irradiation

The study reports a facile synthesis of Ag-g-C3N4/AC composites with highly photocatalytic activity and good adsorption capacity by an impregnation-thermal polycondensation process. The resulting Ag-g-C3N4/AC composites were used for treatment of different pollutants in water including Rhodamine B (RhB), Cr(VI) ions and pathogens. When the precursor mass ratio of urea and AC was 2:2, the resultant Ag-g-C3N4/AC catalyst showed the best photocatalytic performances. In particular, the composite photocatalysts exhibited highly bactericidal efficiency, which could reach 99.9% after 120 min of irradiation. The higher photocatalytic performances of Agg-C3N4/AC composites were attributed to the surface plasmon resonance (SPR) effect of Ag nanoparticles (NPs) together with the interfacial synergistic effects. Meanwhile, AC not only exhibited excellent adsorption capacity, but also decreased aggregation of g-C3N4, which could enhance the separation efficiency of photogenerated charge carriers. It was uncovered through Electron Spin Resonance (ESR) and radical scavenger experiments that center dot OH radicals, center dot O-2 and h(+) participate in the RhB degradation under the visible light. This work shows that the high-efficient and stable Ag-g-C3N4/AC composites have a great potential in the treatment of organic pollutants, toxic heavy metals and pathogenic bacteria by adsorption/photocatalysis for practical water treatment.