Rational design of Spirulina residue-derived graphene oxide as an efficient metal-free catalyst for sulfathiazole removal

Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation has attracted extensive attention in wastewater remediation. Although traditional transition metal or metal oxide-based catalysts exhibit high efficiency in PMS activation, they inevitably suffer from metal leaching. Herein, the Spirulina residue graphene oxide (SRGO) was synthesized as a bio-GO to effectively activate PMS to degrade sulfathiazole (STZ). After analysis, the performance of SRGO was highly related to salinity, and the removal rate of STZ via high-salinity group named as SRGO-HS/PMS system was as high as 100% within 10 min. Moreover, the excellent and stable regeneration of SRGO-HS (>83%) was verified through four consecutive recycling. Notably, electron spin resonance (ESR), electrochemical and quenching experiments clearly indicated that the degradation of STZ in SRGO-HS/PMS was mainly occurred by the non-radical reactions based on singlet oxygen (¹O₂) and electron transfer, suggesting its high sustainability. Together, this work not only provides an appropriate platform for waste biomass conversion, but also offers a new idea for expanding the application of integrating bio-GO and AOPs to remove antibiotics from water.