Effect of preparation method on the structure and photocatalytic performance of BiOI and Bi5O7I for Hg0 removal

Abstract

This paper presents a study on the effect of preparation method on the structure and photocatalytic activities of BiOI and Bi5O7I photocatalysts for elemental mercury (Hg0) removal in a wet bubbling reactor. Two visible-light-driven BiOI photocatalysts (BiOI-HAc and BiOI-EG) via either glacial acetic acid (HAc) coprecipitation or ethylene glycol (EG) hydrothermal synthesis as well as their derivative samples (Bi5O7I-HAc and Bi5O7I-EG) were synthesized, respectively. The photocatalysts were characterized by N2 adsorption-desorption analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoelectrochemical measurement and electron spin resonance (ESR) techniques. The results showed that Bi5O7I-HAc and BiOI-EG exhibited superior Hg0 removal performances in comparison with BiOI-HAc and Bi5O7I-EG, and Bi5O7I-HAc photocatalyst possessed much better activity on SO2 resistance and wider reaction temperature scope than BiOI-EG. The enhancement in Hg0 removal efficiency can be attributed to the appearance of plenty of adsorbed oxygen, efficient photoinduced carrier separations and their special band gap structures. The photoexcited O2− and h+ played key roles in the process of Hg0 removal.