A novel S-scheme heterojunction in spent battery-derived ZnFe2O4/g-C3N4 photocatalyst for enhancing peroxymonosulfate activation and visible light degradation of organic pollutant

Abstract

Waste resource recovery and water pollution control are two important issues in environmental protection. In this study, ZnFe2O4 prepared from spent alkaline Zn-Mn battery was combined with g-C3N4 (CN) to form ZnFe2O4/g-C3N4 (ZFO-CN) step-scheme (S-scheme) heterojunction photocatalyst to eliminate bisphenol A (BPA) in the presence of peroxymonosulfate (PMS) under visible light (Vis, λ ≥ 400 nm). Results revealed that the ZFO-CN possessed an outstanding photocatalytic performance, which was attributed to the superior visible light harvest capacity and unique S-scheme charge transfer pathway as evidenced by X-ray photoelectron spectroscopy and electrochemical test. Reactive species including SO4•−, •OH, •O2−, 1O2 and h+ co-existed in the system, among which the non-radicals including 1O2 and h+ were inferred to be the predominant oxidation species based on the result of chemical quenching experiments. The effects of catalyst dosage, PMS concentration, initial pH and inorganic ion (HCO3−, Cl−, H2PO4−, NO3− or NH4+) on BPA removal were investigated. At 0.3 g L−1 ZFO-CN-0.5, 0.5 mM PMS and 60 min reaction time, more than 97.7% BPA was decomposed under visible light irradiation over a wide pH range of 3.5–9.0. This work provides a promising approach of constructing spent battery-derived spinel oxides into a high-efficiency heterojunction photocatalyst to activate PMS for practical wastewater treatment.