Ag2CO3 anchored on BiOI/CoFe2O4 composites with p-n-p heterojunctions: Highly enhanced activity for photocatalytic oxidation of Hg0 under fluorescent light irradiation

Abstract

Ag2CO3 anchored on BiOI/CoFe2O4 composites with p-n-p heterojunctions were synthesized by means of a facile modified deposition-precipitation method and were utilized to explore their activities for toxic elemental mercury (Hg0) removal under fluorescent light (FSL) irradiation. The obtained samples were characterized via N2 adsorption-desorption, XRD, VSM, SEM, TEM, XPS, EDS, UV–vis DRS, ESR, Transient photocurrent techniques. The Ag2CO3/BiOI/CoFe2O4 composites (AgCBi-CFO-4) with 4 wt. % of Ag2CO3 to BiOI/CoFe2O4 showed remarkably enhanced activity for Hg0 removal, which was ascribed to the combination effect of AgCBi-CFO-4 photocatalyst and FSL irradiation. Photocatalytic activity of AgCBi-CFO-4 increased by 40% and 30% in comparison with BiOI and BiOI/CoFe2O4 samples, respectively. The performance of AgCBi-CFO-4 was greatly influenced by some experimental factors such as FSL irradiation, strongly alkaline solution, CO32− ions and SO2. Due to the formation of intimate p-n-p heterojunction among p-type BiOI, n-type Ag2CO3 and p-type CoFe2O4, the ternary composites exhibited the enhanced visible-light absorbance performance and efficient separation of the charge carriers, thereby exerting a significantly positive effect on photocatalytic activity. The investigation clearly displayed that the superoxide radicals (O2−) generated by AgCBi-CFO-4 photocatalyst were the main contributor to an efficient Hg0 removal.