Enhanced photocatalytic degradation of sulfamethazine by g-C3N4/Cu, N-TiO2 composites under simulated sunlight irradiation

Abstract

The g-C3N4/Cu, N-TiO2 heterojunction photocatalysts were prepared employing co-precipitation and calcination methods in this work. The as-prepared photocatalysts were characterized using several analytical testing methods such as XRD, SEM, EDS, XPS, UV–vis DRS, and photoluminescence spectra. SEM and EDS analysis confirmed the formation of heterojunction between Cu, N-TiO2 and g-C3N4 and uniform distribution of C, N, Ti, and O elements in the CN/Cu, N-TiO2-1 composite photocatalyst. UV–vis DRS analysis displayed that N and Cu co-doping can reduce the band gap of the involved catalysts, leading to improvement of light absorption. Photoluminescence spectra analysis showed that combining Cu, N-TiO2 and g-C3N4 can improve photogenerated charges separation effectively, demonstrating the formation of g-C3N4/Cu, N-TiO2 heterojunction in CN/Cu, N-TiO2-1 composite photocatalyst. The photocatalytic performance of the synthesized catalysts was evaluated under simulated sunlight irradiation via sulfamethazine (SMZ) degradation experiments. The results displayed that g-C3N4/Cu, N-TiO2-1 heterojunction photocatalyst (with a mass ratio of 1:1 of Cu, N-TiO2 to dicyandiamide) showed the optimum performance with a transformation rate of SMZ of 95.80 % under 240 min irradiation. The plausible photocatalytic mechanism involving g-C3N4/Cu, N-TiO2-1 was proposed according to the trapping experiments of active species, which confirmed that O2•− radicals were the primary active component in photocatalytic degradation of SMZ and h+ and •OH also exhibited significant roles. Furthermore, the main pathways for SMZ degradation were proposed by identifying the involved degradation intermediates. The present research indicates that g-C3N4/Cu, N-TiO2 heterojunction photocatalyst is encouraging for the elimination of sulfonamide antibiotics from actual wastewater.