Efficient adsorption and photocatalytic degradation of Rhodamine B under visible light irradiation over BiOBr/montmorillonite composites

Abstract

BiOBr/Na-montmorillonite composites (BiOBr-Mt) were prepared under laboratory ambient conditions by using the surfactant cetyltrimethylammonium bromide (CTAB) as the Br source and template, and the as-synthesized samples were characterized by XRD, FT-IR, FESEM, TEM equipped with EDS, BET and UV-vis DRS techniques. Interestingly, the particle size of BiOBr can be controlled by CTAB modified Na-montmorillonite. The photocatalytic activity of the as-prepared was further evaluated by decomposition of Rhodamine B (RhB) under visible light irradiation; the obtained results revealed that the BiOBr-Mt sample had strong photoabsorption in the visible light region. It has higher photocatalytic activity than pure BiOBr alone. There exists an efficient adsorption for RhB onto BiOBr-Mt contrast to that onto the pure BiOBr. The adsorption processes can be well described by pseudo-second-order kinetic model; meanwhile, the adsorption behaviors can be described by both Freundlich and Langmuir equations but the former was better. Additionally, the relevant adsorption and degradation mechanisms were explored and the possible mechanisms were presented. The photocatalytic activity has high effect both in acidic and basic conditions on the degradation reaction but in acidic condition is more favorable. After three recycles, BiOBr-Mt did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst was essentially stable.

Keywords: Adsorption; BiOBr; CTAB; Montmorillonite; Photocatalytic.