Powder activated carbon/Fe3O4 hybrid composite as a highly efficient heterogeneous catalyst for Fenton oxidation of tetracycline: degradation mechanism and kinetic

Abstract

In this work, we prepared and used a composite of powder activate carbon/Fe₃O₄ magnetic nanoparticles (PAC/Fe₃O₄ MNPs) as a heterogeneous catalyst to remove tetracycline (TC) from aqueous solution. By using XRD, BET, VSM, SEM, TEM and EDX techniques, also, we tried to characterize the catalyst. The effects of pH, H₂O₂, catalyst dosages and also initial TC concentration on the degradation process were assessed. Based on the results, it was indicated that at low pH values and initial TC concentrations, the efficiency of the process is higher than the other values and concentrations studied in this work. Under the ambient conditions and setting the initial pH value and TC concentration at respectively 3.0 ± 0.2 and 10 mg L⁻¹, the optimal dosage of reagents were recorded to be 0.3 g L⁻¹ catalyst and 80.0 mM H₂O₂. The values of observed rate constants, k_obs, increased by increasing the catalyst loading in the system; however, these values decreases when the initial TC concentration was increased. Our findings indicated that all of TC concentration was nearly degraded during the 180 min reaction. Regarding the reusability of PAC/Fe₃O₄ MNPs, the results showed that TC and TOC removal efficiencies of 94.5% and 32.3%, respectively, can be achieved after four consecutive runs. By conducting the stability experiments, it was confirmed that PAC/Fe₃O₄ MNPs is a promising and effective catalyst in Fenton reactions and can be used to treat TC-contaminated water with very low loss of catalytic activity.