Efficient Degradation of Sulfamethoxazole and Assessment of Antioxidant and Antimicrobial Activities with nZVCe/Biochar Composite

Sulfamethoxazole (SMX) is extensively used for the treatment of various infections; however, its widespread application has led to aquatic pollution and raised significant environmental concerns owing to its persistence. For this investigation, biochar (BC) was made using the biomass extract of the Phoenix dactylifera plant. A mesoporous nano-zerovalent cerium/biochar (nZVCe/BC) composite was then synthesized utilizing the pre-prepared biochar and applied for the degradation of SMX, along with an evaluation of its antioxidant and antibacterial activities. The composite exhibited remarkable performance, achieving approximately 77% degradation of SMX, primarily driven by adsorption and ^●OH interactions. The abstraction of SMX was found to be inhibited in the presence of ^●OH scavengers and competing species, highlighting the pivotal role of ^●OH reactivity and adsorption in the degradation mechanism. Additionally, species that effectively competed with SMX for adsorption sites inhibited its removal, thereby influencing the overall mineralization process. The composite demonstrated excellent reusability and stability, maintaining a high level of SMX removal over seven consecutive cycles. Only minimal leaching of Ce ions was observed, confirming the environmental compatibility of the material. Furthermore, the results underscore the critical influence of several parameters—such as pH, initial SMX concentration, nZVCe/BC composite dosage, and the presence of competing species—on the overall degradation efficiency of the composite. Furthermore, the composite exhibited higher antioxidant activity (62% inhibition) compared to BC alone (51%) at a concentration of 500 µg/mL, while ascorbic acid showed the maximum activity with 95% inhibition. Similar patterns were noted in the antimicrobial tests, where the composite demonstrated inhibitory effects against Staphylococcus aureus and Klebsiella pneumoniae, producing inhibition zones of 7 mm and 4 mm, respectively. All things considered, the study offers an ecologically sound approach for creating the nZVCe/BC composite, highlighting its efficiency in SMX removal as well as its promising antioxidant and antimicrobial potential.