Exceptional photo-elimination of antibiotic by a novel Z-scheme heterojunction catalyst composed of nanoscale zero valent iron embedded with carbon quantum dots (CQDs)-black TiO2

Xi Wu; Xiangyu Wang; Iseult Lynch; Zhiling Guo; Peng Zhang; Lisi Wu; Ping Ning; Nanqi Ren

doi:10.1016/j.jhazmat.2023.132323

Exceptional photo-elimination of antibiotic by a novel Z-scheme heterojunction catalyst composed of nanoscale zero valent iron embedded with carbon quantum dots (CQDs)-black TiO₂

J Hazard Mater. 2023 Oct 15:460:132323. doi: 10.1016/j.jhazmat.2023.132323. Epub 2023 Aug 16.

Authors

Xi Wu¹, Xiangyu Wang², Iseult Lynch³, Zhiling Guo³, Peng Zhang³, Lisi Wu³, Ping Ning⁴, Nanqi Ren⁵

Affiliations

¹ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China.
² Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China; School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK. Electronic address: imusthlee2014@sina.com.
³ School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
⁴ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China. Electronic address: ningping58-2015@sina.com.
⁵ School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.

PMID: 37666174
DOI: 10.1016/j.jhazmat.2023.132323

Abstract

Passivation of nanoscale zero valent iron (nZVI, Fe⁰) impaired its longevity while black TiO₂ (b-TiO₂) suffered from restricted optical properties. Using a facile approach, a novel Z-scheme heterojunction catalyst (Fe⁰@CQDs-TiO₂(b)) of nZVI decorated with carbon quantum dots (CQDs) implanted into b-TiO₂ was designed. Characterization results revealed the optical potential of the passivation coating of nZVI. The incorporation of CQDs stimulated the creation of active •OH during the dark reaction, and led to an accelerated mobility of photo-excited carriers of b-TiO₂ and optimized its band gap (narrowing from 2.36 eV to 2.15 eV) during the light reaction. The photo-elimination capacity of metronidazole (MNZ) on Fe⁰@CQDs-TiO₂(b) (99.36%) was 2.64, 8.25 and 1.34 fold beyond that on nZVI, b-TiO₂ and Fe⁰@b-TiO₂, respectively. The assembled material offered excellent adaptability to environmental substrates, in addition to being virtually unaffected by tap (95.62%) and river water (92.62%). The mechanism of MNZ degradation was elaborated, and the combination of density functional theory (DFT) calculations and LC-MS discerned 12 intermediates and 3 routes. Toxicity assessment of these products was conducted to ensure no inadvertent negative environmental impacts arose. This work proposed an original direction and mechanism for the application of passivation layers in nZVI-based materials for environmental restoration.

Keywords: Black TiO(2); Carbon quantum dots; DFT calculations; Nanoscale zero valent iron; Z-scheme heterojunction.