Modified co-pyrolyzed biochar activated persulfate accelerates the degradation of cefixime: antibiotic removal from water and solid waste disposal

In this study, raw biochar (WSBC) was prepared by co-pyrolysis of sludge and wheat straw. Subsequently, Cu ions were loaded onto the catalyst surface via a hydrothermal synthesis method to produce high-performance modified biochar (Cu@WSBC). A complete system was successfully established using Cu@WSBC activated persulfate (PS) to degrade cefixime (CFX) in water. The EDS and XPS results indicate that the metal ions are successfully loaded onto the surface of the biochar. The BET test results clearly demonstrate that the biochar exhibits excellent mesoporous characteristics and that the co-pyrolysis and metal ion modification significantly increase the catalyst's specific surface area. Consequently, this high-performance biochar not only enhances PS activation efficiency but also exhibits optimal CFX degradation performance. Under preset conditions, the Cu@WSBC+PS system removed about 85% of CFX within 30 min, with a degradation rate reaching 93.3% at 1 h. The results of EPR testing and quenching experiments indicate that the degradation of the antibiotic is due to the direct attack on CFX by reactive oxygen species (ROS) generated by the Cu@WSBC+PS system. Based on the LC-MS and TOC results, possible degradation pathways for CFX were inferred, confirming that most of the CFX is mineralized into small-molecule compounds. Furthermore, this study examines the degradation efficacy of CFX in this system under varying water environments and biochar pyrolysis temperatures, as well as the biochar's recyclability. This study provides a new strategy for achieving "treating waste with waste" in the management of solid waste.