Mechanisms
involved in the photocatalytic oxidation of As(III)
are complicated in that various oxidizing species (such as h+, •OH, and O2
•–) have been suggested to play important roles in different photocatalytic
systems. In this study, Bi2.15WO6 shows high
reactivity in the photocatalytic oxidation of As(III) under visible
light. Quenching experiments indicate that apart from h+, the surface superoxo (Bi–OO•)
and peroxo species (Bi–OOH) formed on Bi2.15WO6 also contribute to As(III) oxidation. The increased
production of H2O2 with increasingly consumed
As(III) or with the addition of H-donors such as glucose and various
phenolics further reveals that H-abstraction from As(III) or H-donors
to Bi–OO• and then to Bi–OOH
is an important pathway involved in H2O2 production
and As(III) oxidation. In addition, various characterizations confirm
that the As(III)–O–Bi(III) surface complexes formed
on Bi2.15WO6 enhance the photocatalytic reactivity
of Bi2.15WO6 via the ligand-to-metal charge
transfer pathway. We therefore suggest that dissolved oxygen is sequentially
reduced to Bi–OO• and then to Bi–OOH
on Bi2.15WO6, accompanied by H-abstraction from
adsorbed or aqueous As(III) to Bi–OO• and Bi–OOH with the formation of H2O2 and the oxidation of As(III). This work enriches our understanding
of the mechanisms involved in the photocatalytic oxidation of As(III).
Selective oxidation of cyclohexane to cyclohexanol/ cyclohexanone (KA−oil) is an important chemical process, which is still constrained by low conversion and selectivity and high energy consumption. In this study, Cu-doped mesoporous TiO 2 (Cu-MT) has been successfully synthesized via calcinating MIL-125(Ti) doped with copper acetylacetonate, which shows high reactivity in selective oxidation of cyclohexane to KA−oil by persulfate (PS) with the desirable cyclohexane conversion of 16.8% and a selectivity of 98.0% under mild conditions and the low ratio of PS/cyclohexane of 1:1. A series of characterizations and density functional theory calculations reveal that the doped Cu(I,II) on Cu-MT is the reactive site for non-radical activation of PS with the moderate elongation of the O−O bond in PS, which then abstracts 1H (1H + + 1e − ) from cyclohexane to form Cy • and eventually KA−oil. This study gives new insight on the importance of moderately activated PS in selective oxidation of C−H.
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