Optimization of a textile dye degradation in a recirculating fluidized-bed reactor using magnetite/S2O82- process.

Optimization of Acid Orange 7 (AO7) treatment using heterogeneous Fenton-like method in a recirculating fluidized-bed reactor (FBR) was investigated by using central composite design (CCD). Natural magnetite (NM) as Fenton-like catalyst was characterized using scanning electron microscopy. A nonlinear CCD model was obtained for the prediction of dye degradation as a function of experimental variables such as peroxydisulfate concentration (0.1-0.5 mmol/L), initial AO7 concentration (5-25 mg/L), pH (3-9) and NM dosage (0.25-1.25 g/L) after 105 min of treatment. The calculated results by the model were consistent with the experimental results (R2 = 0.959). Furthermore, the model is suitable to estimate the optimum operational conditions and determine the effects of the parameters for maximum AO7 degradation. Eventually, gas chromatography-mass spectroscopy was used for the recognition of the dye degradation by-products.