Adsorption and photocatalytic degradation of sulfamethoxazole by a novel composite hydrogel with visible light irradiation

A novel hydrogel catalyst (p(HEA/NMMA)-CuS) with the function of adsorption and degradation of organic pollutants in water was successfully synthesized using irradiation polymerization and in situ precipitation methods The composite hydrogel catalyst was characterized by SEM-EDS, TEM, swelling kinetics, zeta potential, TGA, XPS, FTIR and XRD. Besides, the effects and mechanisms of adsorption and degradation of sulfamethoxazole(SMX) as the representative pollutant by p(HEA/NMMA)-CuS hydrogel were observed. The results presented that adsorption process of SMX on complex hydrogel fit well to Langmuir monolayer adsorption, and followed a pseudo-second-order rate equation. The decomposition of SMX by p(HEA/NMMA)-CuS hydrogel in aqueous solution under 500 w visible light achieved balance in 24 h, the removal ratio reached 95.91%, and the SMX was mineralized with 43.56%. Hydroxyl radicals was detected as the reactive species using EPR in the system, degradation intermediates of SMX were further analyzed by LC-TOF-MSMS, a possible pathway for SMX degradation was presented. The degradation mechanism of SMX was also illustrated by theoretical calculations of frontier electron densities. Furthermore, mineralization, stability and regeneration results indicated that the developed hydrogel catalyst, p(HEA/NMMA)-CuS hydrogel, was promising in practical application.