Wei Ding,Xinyuan Wan,Huaili Zheng,Yuyang Wu,Salam Muhammad
Owing to the lower toxicity and mobility of inorganic As(V), the oxidative removal of As(III) is deemed as the optimal approach for arsenic elimination from water. Herein, a synthetic TiO 2 -supported CuO material (Cu-TiO 2 ) was coupled with sulfite (S(IV)) to remove As(III) at neutral pH. The combined process coupled oxidation with adsorption (i.e., As(III) removal by Cu-TiO 2 /S(IV)) was superior than a divided preoxidation-adsorption process (i.e., As(V) removal by Cu-TiO 2 ) for arsenic removal. Attractively, low concentration of As(III) (50−300 μg L −1 ) could be completely removed by Cu-TiO 2 (0.25 g L −1 )/S(IV) (0.5 mM) within 60 min. Mechanism investigations revealed that the efficient As(III) removal was attributed to the continuous oxysulfur radicals (SO x •− ) oxidation and Cu-TiO 2 adsorption. The surface-adsorbed and free sulfate radicals (SO 4 •− ) were further identified as the crucial oxidizing species. The Cu-TiO 2 played the dual roles as a catalyst for S(IV) activation and an absorbent for arsenic immobility. The influence of operating parameters (i.e., As(III) concentration and sulfite dosage) and water chemistry (i.e., pH, inorganic anions, dissolved organic matters , and temperature) on As(III) removal were systematically investigated and optimized. Overall, the proposed process has potential application prospects in rehabilitating the As(III)-polluted water environment using industrial waste sulfite.
Ming Lei,Shun Guo,Zhiying Wang,Lihua Zhu,Heqing Tang
Fast and deep debromination of polybrominated diphenyl ethers (PBDEs) under mild conditions is a challenge in the field of pollution control. A strategy was developed to achieve it by exploiting Cu/TiO2 composites as a noble-metal-free catalyst. Toward the debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE47) as a typical PBDE, the use of Cu/TiO2 as a catalyst and hydrazine hydrate (N2H4·H2O) as a reducing agent yielded a degradation removal of 100% and a debromination efficiency of 87.7% in 3 s. A complete debromination of BDE47 at 1500 mg L–1 was possible by successively adding N2H4·H2O. A debromination pathway involving active H atom species was proposed for the catalytic transfer hydrogenation (CTH) of PBDEs according to the identified degradation intermediates. A mechanism was further clarified by density functional theory calculations: electrons are delivered from N2H4·H2O to the metallic Cu atom via a coordination of N in N2H4·H2O with Cu atoms. The electron-trapped Cu atom interacts with adsorbed BDE47 to form a transition complex, and then the debromination of this complex occurs on the surface of Cu nanoparticles due to the hydrogen donation of N2H4·H2O through the CTH process. The new method provides a highly efficient method to remove brominated pollutants.
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