Ultrarapid and Deep Debromination of Tetrabromodiphenyl Ether over Noble-Metal-Free Cu/TiO Nanocomposites under Mild Conditions.

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/TiO 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/TiO as a catalyst and hydrazine hydrate (NH·HO) 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 was possible by successively adding NH·HO. 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 NH·HO to the metallic Cu atom via a coordination of N in NH·HO 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 NH·HO through the CTH process. The new method provides a highly efficient method to remove brominated pollutants.