Efficient removal of sulfonamides in complex aqueous environments by an N, P-co-doped graphitic biochar: the crucial role of P2O5

Abstract

Sulfonamides (SAs) have long been utilized as synthetic antibiotics against bacterial and protozoan infections. Despite their efficacy, SAs can cause significant environmental toxicity, promoting the development of various elimination techniques. This study aimed to develop a biochar efficient at removing SAs from complex aqueous solutions and is the first to establish the role of P₂O₅ in advanced oxidation processes (AOPs). To do so, a range of biochars was developed. The best-performing biochar (NPBC900) can remove 98.33% of a 20 mg L⁻¹ solution of sulfapyridine within 120 minutes using just 0.1 g L⁻¹ of catalyst and 0.5 mM disulfate, surpassing AOP catalysts developed to date. Furthermore, solution components including inorganic anions and cations and natural organic matter have almost no effect on the sulfonamide elimination efficiency, which we demonstrated by testing several natural waters. In this system, it was observed that ¹O₂ and electron transfer played the greatest roles in the overall oxidation process. The best biochar, NPBC900, exhibited exceptional stability and reusability, and the degradation byproducts including residual sulfapyridine did not show any noticeable phytotoxicity. This study presents a cost-effective solution for environmental sulfonamide remediation and underscores the vital role of P₂O₅ in AOPs.