The oxidation treatment of pharmaceutical wastewater in H₂O₂ and PMS system by Iron-containing biochar originated from excess sludge

Advanced oxidation processes (AOPs) have promising applications in wastewater treatment. Metal-containing sludge-based biochar (BC), with the advantages of abundant biomass resources, has received increasing attention as an AOP catalyst. In this study, biochar was used as a catalyst for peroxymonosulfate (PMS) activation and hydrogen peroxide catalyzing in combination with light illumination for organic wastewater degradation. Ironcontaining sludge-based biochar (5%FeBC, 10%FeBC and 20%FeBC) was prepared using excess sludge doped with different amounts of Fe(III) by anaerobic carbonization process with partial reduction of Fe(III) to Fe(II). Xray photoelectron spectroscopy (XPS) spectra showed that most of the Fe in BC existed in the form of Fe(II), with Fe(II) proportion of 61.53 % and Fe(III) of 38.47 %. For PMS activation under light illumination, 5%FeBC prepared at 900 degrees C showed 98 % removal efficiency of tetracycline (TC). The TC removal efficiency of 98 % was obtained under the condition of H2O2 combined with light illumination by 20 % FeBC prepared at 900 degrees C. The reactive substances included sulfate radicals (center dot SO4-), hydroxyl radicals ((OH)-O-center dot) and singlet oxygen (O-1(2)) in the PMS activation system, which contained center dot OH and O-1(2) in the H2O2 system. The 5%FeBC-900 in PMS system and the 20%FeBC-900 in H2O2 system can effectively remove organic matter and proteins from pharmaceutical wastewater.