Water treatment plant sludge as iron source to catalyze a heterogeneous photo–Fenton reaction

Abstract In this work, water treatment plant sludge (WTP) was employed as an alternative heterogeneous photo–Fenton catalyst towards amaranth dye removal from aqueous solution. WTP sludge was calcined at 600 °C and posteriorly characterized by X–ray fluorescence (XRF), X–ray powder diffraction (XRD), Fourier–transform infrared spectroscopy (FTIR), N 2 adsorption/desorption isotherms and scanning electron microscopy (SEM). The results indicated that the material was composed by 12.6 wt% of Fe2O3, and has mesoporous structure, with an average pore diameter of 13.2 mm, pore volume of 0.2 cm3 g − − 1 , and specific surface area of 60 m2 g − − 1 . The optimum experimental conditions for the photo–Fenton reaction were determined by a central composite rotational design (CCRD) coupled with response surface methodology (RSM). A decolorization efficiency of 97% was achieved at pH = 2.8, concentration of H 2 O 2 = 5 . 5 mmol L − − 1 , and catalyst mass of 0.75 g L − − 1 . These results indicated that the calcined sludge has potential to be employed as an alternative catalyst in photo–Fenton reaction to degrade organic molecules present in liquid effluents.