Effective degradation of chloramphenicol in wastewater by activated peroxymonosulfate with Fe-rich porous biochar derived from petrochemical sludge

Excess sludge produced from biological wastewater treatment plant in petroleum industry is a kind of hazardous solid waste. Converting the sludge into biochar catalysts may help to reduce its environmental risk, recover resources and increase economic efficiency. However, the role of the sludge biochar in persulfate activation remains unclear, limiting its application in removing organic pollutants from water body. In this study, metalrich petrochemical sludge was used to produce activated sludge biochar (ASC) via a two-step method of pyrolytic carbonization (400 degrees C-800 degrees C) and subsequent KOH activation (abbreviated as ASC 400-800). The physiochemical properties of ASC 400-800 were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and Raman. The chloramphenicol (CAP) removal performances of ASC 400-800/peroxymonosulfate (PMS) systems were evaluated. Results showed that porous sludge biochar was successfully prepared by the two-step method. At 800 degrees C, the specific surface area of ASC reached the highest value of 202.92 m2 g-1. At 600-800 degrees C, Fe3O4, Fe0, and graphitized carbon were formed in ASC. Among ASC 400-800, ASC 800 exhibited the best CAP removal performance in ASC 800/PMS system by adsorption combined with catalytic degradation. The optimal conditions identified for 0.31 mM CAP removal were ASC 800 2.0 g L-1, PMS 6.2 mM, and pH 2.0. SO4 center dot-, center dot OH, and 1O2 may contribute to CAP degradation. The degradation pathways of CAP were proposed based on the identified degradation intermediates. Overall, this study confirmed that porous biochar derived from petrochemical sludge was an effective adsorbent or PMS catalyst to remove organic pollutants from wastewater.

Automated summary

Excess sludge in petroleum industry can be converted into biochar catalysts to reduce environmental risk and recover resources. In this study, activated sludge biochar (ASC) was produced from petrochemical sludge and its chloramphenicol (CAP) removal performance was evaluated. The results showed that ASC 800 exhibited the best CAP removal performance. The study confirmed that porous biochar derived from petrochemical sludge is effective for removing organic pollutants from wastewater.