title: Cu2O-promoted degradation of sulfamethoxazole by α-Fe2O3-catalyzed peroxymonosulfate under circumneutral conditions: synergistic effect, Cu/Fe ratios, and mechanisms.
abstract: To promote the application of iron oxides in sulfate radical-based advanced oxidation processes, a convenient approach using Cu2O as a catalyst additive was proposed. Composite catalysts based on α-Fe2O3(CTX%Cu2O, X = 1, 2.5, 5, and 10) were prepared for peroxymonosulfate (PMS) activation, and sulfamethoxazole was used as a model pollutant to probe the catalytic reactivity. The results show that a synergistic catalytic effect exists between Cu2O and α-Fe2O3, which was explained by the promoted reduction of Fe(III) by Cu(I). Iron K-edge X-ray absorption spectroscopy investigations indicated that the promoted reduction probably occurred with PMS acting as a ligand that bridges the redox centers of Cu(I) and Fe(III). The weight ratio between Cu2O and α-Fe2O3influenced the degradation of sulfamethoxazole, and the optimal ratio depended on the dosage of PMS and catalysts. With 40 mg L-1PMS and 0.6 g L-1catalyst, a pseudo-first-order constant of ∼0.019 min-1was achieved for CT2.5%Cu2O, whereas only 0.004 min-1was realized for α-Fe2O3. Nearly complete degradation of the sulfamethoxazole was achieved within 180 min under the conditions of 40 mg L-1PMS, 0.4 g L-1CT2.5%Cu2O, and pH 6.8. In contrast, less than 20% degradation was realized with α-Fe2O3under similar conditions. The CT2.5%Cu2O catalyst had the best stoichiometric efficiency of PMS (0.317), which was 4.5 and 5.8 times higher than those of Cu2O (0.070) and α-Fe2O3(0.054), respectively. On the basis of the products identified, the cleavage of the S-N bond was proposed as a major pathway for the degradation of sulfamethoxazole.
authors.affiliation: a Department of Civil Engineering , The University of Hong Kong , Hong Kong.
authors.forename: Yong
authors.initials: Y
authors.lastname: Feng
authors.affiliation: a Department of Civil Engineering , The University of Hong Kong , Hong Kong.|b Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control , Guangdong Institute of Eco-Environmental and Soil Sciences , Guangzhou , People's Republic of China.
authors.forename: Changzhong
authors.initials: C
authors.lastname: Liao
authors.affiliation: a Department of Civil Engineering , The University of Hong Kong , Hong Kong.
authors.forename: Hangkong
authors.initials: H
authors.lastname: Li
authors.affiliation: b Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control , Guangdong Institute of Eco-Environmental and Soil Sciences , Guangzhou , People's Republic of China.
authors.forename: Chengshuai
authors.initials: C
authors.lastname: Liu
authors.affiliation: a Department of Civil Engineering , The University of Hong Kong , Hong Kong.
authors.forename: Kaimin
authors.initials: K
authors.lastname: Shih
mesh_terms: D003300:Copper / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D010545:Peroxides / Q000737:chemistry; D013420:Sulfamethoxazole / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D010545:Peroxides; D014874:Water Pollutants, Chemical; C000499:ferric oxide; C038288:peroxymonosulfate; D003300:Copper; D007501:Iron; D013420:Sulfamethoxazole
keywords: Cu2O; Peroxymonosulfate; sulfamethoxazole; synergistic effect; α-Fe2O3