Simulated solar light photooxidation of azocarmine B over hydroxyl iron–aluminum pillared bentonite using hydrogen peroxide

• Hydroxy-iron–aluminum pillared bentonite shows high photocatalytic activity.
• Box–Behnken design was used to optimize operating variables.
• The optimum operating conditions for azocarmine B degradation were found.
• A tentative pathway for the oxidative degradation of azocarmine B was postulated.

Hydroxy iron–aluminum pillared bentonite (FeAlPBent) was synthesized with ion exchange method. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), BET, UV–vis diffuse spectra. The photo-Fenton catalytic activity of FeAlPBent was tested under a different reaction condition using azocarmine B (ACB) as model pollutant under simulated solar light irradiation. Response surface methodology based on Box–Behnken design was employed to investigate the effects of process variables on the removal of azocarmine B. The results indicated that hydroxy aluminum iron ions intercalated into the interlayer spaces of bentonite successfully and FeAlPBent had high photocatalytic activity. The optimum conditions for ACB removal were dye concentration of 80 mg/L ACB, pH 3, H2O2 concentration of 20 mM and catalyst dosage of 0.6 g/L. Under these conditions, the maximum ACB decolorization efficiency and TOC removal were 99.3% and 73.9%, respectively. In addition, the experiments also illustrated that FeAlPBent had a long-term stability. Furthermore, a tentative pathway for the oxidative degradation of ACB was postulated by Gaussian calculation and GC–MS analysis.