Efficient degradation of sulfamethoxazole under visible light irradiation by polyaniline/copper sulfide composite photocatalyst.

A novel composite photocatalyst polyaniline/copper sulfide (PANI/CuS) was successfully prepared using an in situ precipitation method. The surface morphology, internal structure, thermal stability, electronegativity, and visible light photocatalytic activity of PANI/CuS were analyzed by a series of characterization methods. Sulfamethoxazole (SMX) was used as the representative pollutant; the degradation effect, degradation kinetic, and influencing factor of SMX by PANI/CuS under visible light were systematically investigated. The degradation mechanism of SMX by PANI/CuS was explained by a series of free radical quenching experiments and electron paramagnetic resonance spectroscopy experiments. The following were the main conclusions through the above research. First, the degradation effect of SMX by composite PANI/CuS was better than that by pure CuS under the same experimental conditions, which indirectly proved that the addition of PANI could effectively delay the photochemical corrosion of CuS. Next, when the dosage of PANI/CuS was 0.04 g/L, initial concentration of SMX was 5 ppm, pH was 2.0, and the simulated visible light was 500 W, the degradation effect of SMX was as high as 72.13%. Last, the hole (h) played a major role and the superoxide radical (·O) played an auxiliary role in the degradation process of SMX by PANI/CuS; persistent free radicals exist simultaneously.