Activation of peroxymonosulfate by iron-containing sewage sludge pyrolytic hydrochar-based catalyst for efficient treatment of process water

Hydrothermal carbonization (HTC) is considered as a promising method for the treatment of sewage sludge (SS). However, the management of process water (PW) has emerged as a critical bottleneck to its sustainable development. In this study, pyrolytic hydrochar (PHC) derived from SS was prepared integrating HTC and pyrolysis for peroxymonosulfate (PMS)-assisted treatment of PW. The influence of HTC temperature, pyrolysis temperature, and exogenous iron on the degradation efficiency of soluble chemical oxygen demand (SCOD) in PW was examined. Results indicate that increasing the pyrolysis temperature enhances SCOD degradation in PW by further promoting the reduction of iron oxides and nitrogen self-doping in PHC. Therefore, the optimal SCOD degradation efficiency reaches 61.50 % with PHC4Fe-800 under the conditions of [PHC] = 0.5 mg center dot L- 1 and [PMS] = 0.5 mg center dot L- 1. XRD, XPS and Raman analyses confirm the presence of active sites, including iron compounds (i. e., Fe3O4, Fe) and graphitic N. Electron paramagnetic resonance (EPR) analysis reveals the free radicals of SO4 & sdot;and HO & sdot; are involved in SCOD degradation. Herein, the correspoding PMS activation mechanism is proposed. This work provides a sustainable approach for both the treatment of PW and the conversion of SS into functionalized carbon materials.