Charge transfer mechanism through S-scheme heterojunction in in-situ synthesized TiO2/Fe-doped hydroxyapatite for improved photodegradation of xanthate

Kaiqian Shu; Chitiphon Chuaicham; Yuto Noguchi; Longhua Xu; Keiko Sasaki

doi:10.1016/j.jhazmat.2023.132337

Charge transfer mechanism through S-scheme heterojunction in in-situ synthesized TiO₂/Fe-doped hydroxyapatite for improved photodegradation of xanthate

J Hazard Mater. 2023 Oct 15:460:132337. doi: 10.1016/j.jhazmat.2023.132337. Epub 2023 Aug 16.

Authors

Kaiqian Shu¹, Chitiphon Chuaicham¹, Yuto Noguchi¹, Longhua Xu², Keiko Sasaki³

Affiliations

¹ Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishiku, Fukuoka 819-0395, Japan.
² Key Laboratory of Solid Waste Treatment and Resource Recycle Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, Sichuan, PR China.
³ Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishiku, Fukuoka 819-0395, Japan. Electronic address: keikos@mine.kyushu-u.ac.jp.

PMID: 37647669
DOI: 10.1016/j.jhazmat.2023.132337

Abstract

The heterojunction structure of the photocatalyst composite, which necessitates a robust interface and sufficient contact areas, holds the key to obtaining high charge carrier migration efficiency. Here, a novel composite, TiO₂ nanoparticles/Fe-doped hydroxyapatite (TONPs/FH_CS), is fabricated using a two-step synthetic technique, in which FH_CS is synthesized from artificial converter slag enriched with Fe and Ca. The unique nanorod@plate structure of FH_CS enables the uniform immobilization of TONPs onto FH_CS. Thereby, an n-n type heterojunction exhibits a highly intimate Ti-O-Fe heterointerface. Kelvin probe testing demonstrates the formation of an interfacial electric field oriented from FH_CS to TONPs, which serves as the driving force for interfacial electron transfer through the Ti-O-Fe channels. The photoacoustic signals provide information on electron trap levels and densities, indicating the formation of the electron transfer channels. •O₂^- and •OH species are responsible for being the active species in this system. A photoexcited carrier transfer pathway exhibiting an S-scheme mechanism with high separation efficiency significantly enhances the utilization of charge carriers in each phase. Thus, improved xanthate degradation has been achieved using a heterojunction containing a photocatalyst derived from industrial solid waste. This work demonstrates the significant potential of steel-making byproduct utilization in industrial wastewater treatment.

Keywords: Artificial converter slag; Fe-doped hydroxyapatite; Interfacial charge transfer; Titanium dioxide; Xanthate photodegradation.