Removal of Rhodamine B with Fe-supported bentonite as heterogeneous photo-Fenton catalyst under visible irradiation

Fe-supported bentonite (Fe-B) was successfully fabricated as a low-cost heterogeneous catalyst for adsorption and visible light photo-Fenton degradation of Rhodamine B (RhB) from aqueous solution. The support of iron rendered a significant increase in specific surface area and a slight increase in interlayer spacing of bentonite, thus improving the adsorption performance of Fe-B. The maximum adsorption capacity of RhB onto Fe-B was calculated to be 227.27 mg g(-1) by the fitting of Langmuir adsorption isotherm. The catalytic activity of Fe-B was evaluated by the degradation of RhB (80 mg L-1) in the presence of H2O2 under visible light irradiation. Light-emitting diodes (LED) lamps were used as visible light source as they are small in size, energy efficient, compact, have a relatively long life span, and can be facile to operate. The estimated quantum yield of photodegradation of RhB was calculated as (1.66 +/- 0.21) x 10(-2). The results showed that the Fe-B catalyst demonstrated good performance in the removal of RhB by combination of adsorption and degradation with optimum operating conditions of Fe-B 0.25 g L-1, natural pH 4.2 and H2O2 12 mM. The Fe-B catalyst retained high visible light photocatalytic activity toward RhB in a wide pH range from 3.0 to 9.0 and exhibited good chemical stability after five consecutive adsorption/degradation cycles. (C) 2014 Elsevier B.V. All rights reserved.