LED-driven Hematite/Bi4O5I2 nanocomposite as S-scheme heterojunction photocatalyst for efficient degradation of phenolic compounds in real wastewater

Abstract

Heterojunction-based photocatalysts have recently emerged as a promising solution for removing organic pollutants from wastewater, especially those synthesized using low-carbon footprint methods. In view of this, the present work is focused on fabricating Hematite/Bi4O5I2 (HBI) heterojunction nanocomposites under ambient conditions using a natural Hematite source, employing a sustainable and eco-friendly approach. The HBI nanocomposites were synthesized via an in-situ chemical precipitation method and subsequently utilized to degrade phenolic compounds (PCs) in various real water matrices. The construction of the heterojunction was validated using different characterization techniques. Our findings indicated complete bisphenol A (BPA) photo-disintegration by 30% Hematite into Bi4O5I2 (HBI-30) within 80 min under LED light irradiation. Kinetic studies revealed the apparent rate constant of HBI-30 to be 106 and 8.8 times superior to bare Hematite and Bi4O5I2, respectively, attributed to the improved charge separation and visible light absorption enabled by the S-scheme heterojunction. Superoxide radicals (•O2-) were identified as a primary reactive species in the breakdown of BPA. The HBI-30 also exhibited superior performance in degrading a mixture of PCs (including BPA, m-cresol, and phenol) in DI water; however, its efficiency was notably reduced in secondary wastewater treatment plant effluent. Post-treatment analysis showed no adverse effects on E. coli proliferation, indicating reduced toxicity of aqueous PCs after photocatalysis. HBI-30 demonstrated remarkable chemical and physical stability, with negligible leaching while maintaining 81.23% BPA degradation efficiency after ten reuse cycles. Additionally, HBI-30 was immobilized onto polyurethane foam, enabling the simultaneous and effective elimination of PCs. These findings demonstrate that the fabricated HBI-30 heterojunction is an efficient photocatalyst capable of decomposing PCs from complex aquatic environments.