FeCl3-activated biochar catalyst for heterogeneous Fenton oxidation of antibiotic sulfamethoxazole in water

One-step FeCl3-mediated pyrolysis/activation was developed for preparation of bermudagrass (BG)-derived FeCl3-activated biochars (FA-BCs) from bermudagrass (BG) as a heterogenous Fenton catalyst for heterogeneous Fenton oxidation of sulfamethoxazole (SMX) in water. The FA-BC prepared at the FeCl3 to BG mass ratio of 2 (FA-BC) exhibited higher adsorption and Fenton oxidation of SMX than other mass ratios of the FeCl3 to BG. FA-BC presented the great surface area (835 m2/g) and high SMX adsorption capacity (195 mg SMX/g BC), which was higher than various BCs in the previous studies. Additionally, the surface of FA-BC was attached with Fe2O3, Fe0, and Fe3O4 after the FeCl3 activation. Under the optimal conditions for Fenton reaction (SMX concentration, 100 mg/L; loading of FA-BC, 0.1 g/L; dose of H2O2, 200 mg/L; temperature, 20 °C; pH 3; reaction time, 12 h), SMX and COD removal efficiencies reached 99.94% and 65.19%, respectively. Increasing reaction temperature from 20 to 50 °C significantly improved the SMX oxidation rate from 0.46 to 1.04 h-1. The HO· radicals were proved to play a major role during the Fenton oxidation of SMX. In addition, the SMX solution treated by Fenton oxidation showed much less toxicity than the initial SMX solution. Additionally, the reusability tests of FA-BC indicated that 89.58% removal efficiency for SMX was still achieved after 3 cycles of Fenton oxidation under the optimal conditions. Furthermore, FA-BC can also efficiently remove SMX from the dairy wastewater. Therefore, FA-BC showed a high potential to eliminate aqueous SMX through adsorption and heterogeneous Fenton oxidation.