Fabrication of Z-scheme Bi7O9I3/g-C3N4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants

Lingli Zhu; Dekui Shen; Huiyan Zhang; Kai Hong Luo; Chong Li

doi:10.1016/j.jhazmat.2022.130663

Fabrication of Z-scheme Bi₇O₉I₃/g-C₃N₄ heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants

J Hazard Mater. 2023 Mar 15:446:130663. doi: 10.1016/j.jhazmat.2022.130663. Epub 2022 Dec 22.

Authors

Lingli Zhu¹, Dekui Shen², Huiyan Zhang³, Kai Hong Luo⁴, Chong Li⁵

Affiliations

¹ Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
² Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China. Electronic address: 101011398@seu.edu.cn.
³ Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China. Electronic address: hyzhang@seu.edu.cn.
⁴ Department of Mechanical Engineering, University College London, London WC1E7JE, UK.
⁵ School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, PR China.

PMID: 36608584
DOI: 10.1016/j.jhazmat.2022.130663

Abstract

Chromium(VI) (Cr(VI)), a highly toxic metal ion, generally co-exists with organic pollutants in industrial effluents. The clean and effective technology for water purification is an imperative issue but still a challenging task. A series of Bi₇O₉I₃/g-C₃N₄ (BOI/CN) composites modified by lignin-derived carbon quantum dots (CQDs) were fabricated by hydrothermal method and applied for synchronous photocatalytic removal of Cr (Ⅵ) and levofloxacin (LEV). With the modification of CQDs in BOI/CN heterojunction, the 0.5-CQD/BOI/CN photocatalyst (0.5% content of CQDs) exhibited stronger light-harvesting capacity, more efficient charge separation, and faster electron transfer. Compared to those of BOI (51.2%), CN (36.8%), and BOI/CN (74.4%), the photoreduction efficiency of Cr(VI) reached up to 100% by 0.5-CQD/BOI/CN under 60 min of light irradiation, together with 94.8% degradation efficiency of LEV. The degradation of LEV was dominantly controlled by active species (•OH and •O₂^-) identified by electron paramagnetic resonance analysis and free radical trapping experiments. The intermediates of LEV were determined by LC-MS and the possible degradation pathway was speculated in combination with density functional theory calculation, involving defluorination, decarboxylation, quinolone rings opening, and piperazine moieties oxidation reactions. This work provides an advanced strategy for the fabrication of high-efficiency CQDs-based Z-scheme photocatalysts for environmental remediation.

Keywords: Cr(VI); Heterojunction; Levofloxacin; Lignin-derived carbon quantum dots; Synchronous photocatalytic removal.