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. Iron-containing 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). X-ray 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 °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 °C. The reactive substances included sulfate radicals (·SO4−), hydroxyl radicals (OH) and singlet oxygen (1O2) in the PMS activation system, which contained OH and 1O2 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.