Dual-iodine-doped BiOIO3: Bulk and surface co–modification for enhanced visible-light photocatalytic removal of bisphenol AF

Abstract

Developing effective and feasible treatment methods to address high-risk emerging contaminants is a tremendous and persistent challenge to environmental safety. Bisphenol AF (BPAF), one of the most often used bisphenol A (BPA) alternatives, has a higher lethality, estrogenic activity, and developmental toxicity than BPA, and is difficult to decompose, yet studies to remove BPAF are very limited. Herein, by analysis and design of band structure, single bulk-doped, single surface-doped, and bulk and surface dual-iodine-doped BiOIO3 photocatalysts are fabricated via modifying pristine BiOIO3 using ion exchange or/and in situ reduction strategies. The respective role and synergistic effect of iodine doping at different locations of BiOIO3 are then discussed. As dual doping mode affords a high iodine content, rich oxygen vacancies, and more dispersed band structure, the as-synthesized dual-iodine-doped BiOIO3 exhibits strong visible-light absorption (from UV to ~ 750 nm), strong oxidation ability (valence band potential of 2.68 V), and efficient charge separation kinetics, resulting in an excellent visible-light photocatalytic activity for BPAF degradation. After 2 h of photoreaction, the degradation percentage and TOC reduction of BPAF reach 96.5% and 94.0%, respectively, which far exceed those of BiOIO3, BiOI, or single iodine-doped BiOIO3. The radical trapping experiments and EPR analysis reveal that h+, e−, O2−, OH, and 1O2 are all involved in the catalytic process. The reaction intermediates are identified, and a reasonable photocatalytic mechanism is proposed. In addition, the synthetic dual-iodine-doped photocatalyst maintains stability during photoreaction and is successfully applied to a real wastewater sample, demonstrating its potential in practical applications.