PH-dependent photochemical transformation of arsenic sulfide sludge catalyzed by Fe ions under visible light irradiation

Lu, H., Wang, C., Liu, X., Zhang, J., Lin, Z., Hao, Z. and Pan, G. ORCID: 0000-0003-0920-3018, 2021. PH-dependent photochemical transformation of arsenic sulfide sludge catalyzed by Fe ions under visible light irradiation. Applied Catalysis B: Environmental, 293: 120186. ISSN 0926-3373

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Abstract

The fate of arsenic sulfide sludge (ASS), a typical precipitationproduct of acid smelting wastewater, is readily affected by the surrounding conditions when deposited in environment. When exposed to sunlight, the dissolution and oxidation of ASS were markedly accelerated. However, the photocatalytic transformation mechanism of ASS is still unclear. Herein, the release and oxidation of As(III) in ASS under visible light was investigated by employing artificial arsenic sulfide with Fe(II)/Fe(III) ions. Results show that the coexisting ferric ions are critical to promote the photo-oxidation of As(III) released from the parental solid into As(V). The photo-oxidation rate can reach 149 μM/h in the presence of 0.5 mM Fe(II) ions at pH 1.3, ~5 times of that in the absence of Fe(II). The pH-dependent mechanism of photocatalytic oxidation of As(III) stimulated by Fe(II) ions is proposed and verified. In acid conditions (pH 1.3 and 3), photo-generated hydroxyl and sulfate radicals were promoted by Fe(II)/Fe(III) cycling catalysis with the assistance of the reductive sulfur species from ASS, e.g. S2-and SO32-, and thus accelerated the oxidation of As(III). While at pH 7, the nascent ferric hydroxide colloids enhanced the oxidation rate of As(III) via photo-induced ligand-to-metal-charge transfer (LMCT) mechanism. These findings can help in predicting and controlling the fate of real arsenic-containing sludge in sunlit environments.

Item Type: Journal article
Publication Title: Applied Catalysis B: Environmental
Creators: Lu, H., Wang, C., Liu, X., Zhang, J., Lin, Z., Hao, Z. and Pan, G.
Publisher: Elsevier BV
Date: 21 September 2021
Volume: 293
ISSN: 0926-3373
Identifiers:
NumberType
10.1016/j.apcatb.2021.120186DOI
1431657Other
S092633732100312XPublisher Item Identifier
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Record created by: Jeremy Silvester
Date Added: 30 Apr 2021 09:24
Last Modified: 31 May 2021 15:03
URI: http://irep.ntu.ac.uk/id/eprint/42789

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