An efficient and robust exfoliated bentonite/Ag 3 PO 4 /AgBr plasmonic photocatalyst for degradation of parabens.

Efficient visible-light-driven heterojunction photocatalysts have attracted broad interest owing to their promising adsorption and degradation performances in the removal of organic pollutants. In this study, a mesoporous exfoliated bentonite (EB)/Ag 3 PO 4 /AgBr (30%) photocatalyst was obtained by stripping and exfoliating bentonite as the support for loading Ag 3 PO 4 and AgBr. The particle size ranges of Ag 3 PO 4 and AgBr were about 10-30 nm and 5-10 nm, respectively. The exfoliated bentonite could greatly improve the dispersion and adsorption of Ag 3 PO 4 and AgBr, and significantly enhance the stability of the material during paraben photodegradation. 0.2 g L -1 methylparaben (MPB) was completely decomposed over the EB/Ag 3 PO 4 /AgBr (30%) in 40 min under visible light irradiation. In addition, the photocatalytic activity of EB/Ag 3 PO 4 /AgBr (30%) remained at about 91% after five recycling runs manifesting that EB/Ag 3 PO 4 /AgBr (30%) possessed excellent stability. Radical quenching tests revealed that holes (h + ) and hydroxyl radicals (·OH) were the major radicals. They attacked the side chain on the benzene ring of parabens, which were gradually oxidized to the intermediates, such as benzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, azelaic acid, and eventually became CO 2 and H 2 O. The enhancement of photocatalytic activity and photo-stability could be ascribed to the stable structural characteristics, enlarged surface area, high absorption ability, and improved light absorption ability from loading Ag 3 PO 4 onto EB. Meanwhile, the matched energy levels of Ag 3 PO 4 and AgBr made the photoelectron-hole pairs separate and transfer effectively at the interfaces. As a result, the photocatalytic properties of EB/Ag 3 PO 4 /AgBr (30%) composites were enhanced.