Abstract
The removal of metronidazole (MNZ) from aqueous solutions by the electro-persulfate (EC–PS) process was performed in combination with magnetic Fe 3 O 4 @activated carbon (AC) nanocomposite. In the first step, the Fe 3 O 4 @AC nanocomposites were synthesized and characterized using energy-dispersive X-ray spectroscopy (XRD), vibrating-sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), mapping, and Fourier-transform infrared spectroscopy (FTIR) analysis. The effect of Fe 3 O 4 @AC, PS and EC processes were studied separately and in combination and finally, the appropriate process for MNZ removal was selected. The effect of key parameters on the EC–Fe 3 O 4 @AC–PS process including pH, Fe 3 O 4 @AC dosage, initial MNZ concentration, and PS concentration were investigated. Based on the results obtained, the Fe 3 O 4 @AC had a good structure. The MNZ removal in EC, PS, Fe 3 O 4 @AC, EC–Fe 3 O 4 @AC, EC–PS, EC–Fe 3 O 4 @AC–NaCl, EC–Fe 3 O 4 @AC–PS, and EC–Fe 3 O 4 @AC–PS–NaCl processes were 0, 0, 59.68, 62, 68.94, 67.71, 87.23 and 88%, respectively. Due to the low effect of NaCl insertion on the EC–Fe 3 O 4 @AC–PS process, it was not added into the reactor and optimum conditions for the EC–Fe 3 O 4 @AC–PS process were determined. Under ideal conditions, including MNZ = 40 mg/L, Fe 3 O 4 @AC dose = 1 g/L, pH = 3, PS concentration = 1.68 mM, current density (CD) = 0.6 mA/cm 2 and time = 80 min, the MNZ removal was 92%. Kinetic study showed that the pseudo-second-order model was compatible with the obtained results. In the isotherm studies, the Langmuir model was the most consistent for the data of the present study, and the Q max for Fe 3 O 4 @AC dose from 0.25 to 1 g/L was 332 to 125 mg/g, respectively.