Investigation of the efficiency of BiOI/BiOCl composite photocatalysts using UV, cool and warm white LED light sources - Photon efficiency, toxicity, reusability, matrix effect, and energy consumption

Máté Náfrádi; Klara Hernadi; Zoltán Kónya; Tünde Alapi

doi:10.1016/j.chemosphere.2021.130636

Investigation of the efficiency of BiOI/BiOCl composite photocatalysts using UV, cool and warm white LED light sources - Photon efficiency, toxicity, reusability, matrix effect, and energy consumption

Chemosphere. 2021 Oct:280:130636. doi: 10.1016/j.chemosphere.2021.130636. Epub 2021 Apr 23.

Authors

Máté Náfrádi¹, Klara Hernadi², Zoltán Kónya³, Tünde Alapi⁴

Affiliations

¹ Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720, Szeged, Dóm tér 7, Hungary.
² Department of Applied and Environmental Chemistry, University of Szeged, H-6720, Szeged, Rerrich Béla tér 1, Hungary; Institute of Physical Metallurgy, Metal Forming and Nanotechnology, University of Miskolc, HU-3515, Miskolc, Egyetemváros, Hungary.
³ Department of Applied and Environmental Chemistry, University of Szeged, H-6720, Szeged, Rerrich Béla tér 1, Hungary.
⁴ Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720, Szeged, Dóm tér 7, Hungary. Electronic address: alapi@chem.u-szeged.hu.

PMID: 33975237
DOI: 10.1016/j.chemosphere.2021.130636

Abstract

BiOI, BiOCl, and their composites (BiOI:BiOCl) with molar ratios from 95:5 to 5:95 were synthesized and tested in the transformation of methyl orange (MO) and sulfamethoxypyridazine (SMP) antibiotic, using three various LED light sources: UV LEDs (398 nm), cool and warm white LEDs (400-700 nm). The 80:20 BiOI:BiOCl photocatalyst showed the best adsorption capacity for MO and enhanced activity compared to BiOI and BiOCl. The apparent quantum yield (Φ_app) of the MO and SMP transformation for cool and warm white light was slightly lower than for 398 nm UV radiation. The effect of methanol and 1,4-benzoquinone proved that the transformation is initiated mainly via direct charge transfer, resulting in the demethylation of MO and SO₂ extrusion from SMP. The change of photocatalytic efficiency was followed during three cycles. After the first one, the transformation rates decreased, but there was no significant difference between the second and third cycles. The decreased efficiency is most probably caused by the intermediates, whose continuous accumulation was observed during the cycles. Ecotoxicity measurements confirmed that no toxic substances were leached from the catalyst, but the transformation of both MO and SMP results in toxic intermediates. Using 80:20 BiOI:BiOCl and LED light source, the energy requirement of the removal is about half of the value determined using TiO₂ and a mercury vapor lamp. The effect of some components of wastewater (Cl^-, HCO₃^- and humic acids), pH, and two matrices on the composite photocatalysts' efficiency and stability were also investigated.

Keywords: BiOX; Photocatalysis; Quantum yield; Visible light.

MeSH terms

Adsorption
Bismuth*
Catalysis
Light
Ultraviolet Rays*

Substances

Bismuth