An economical pyrrhotite-loaded sludge carbon composite effectively activated persulfate to sterilize Escherichia coli
BACKGROUND Persulfate (PS) has the capability to yield free radicals via activators, thereby shaping an advanced oxidation process that can significantly contribute to effective sterilization. Central to this technology is the pursuit of appropriate activators. RESULTS In our research, we successfully synthesized an economical and efficient PS activator, namely a pyrrhotite-loaded sludge carbon (Pyr-SC) composite. This was achieved via a straightforward procedure utilizing two environmentally friendly and cost-efficient raw materials: pyrite and sludge. Pyr-SC exhibited a specific surface area of 60.4 m 2 g −1 and rich functional groups such as carbon–sulfur and sulfur–oxygen. The magnetic and graphitic carbon structures were formed at high temperatures during the preparation process, and the sludge carbon (SC) exhibited porous defects, which allowed the effective insertion of iron/sulfur into SC to form the stable Pyr-SC structure. Pyr-SC activated PS, which further sterilized Escherichia coli in the wastewater at a sterilization rate of 7.00 lg E. coli at 10 7 cfu mL −1 in 80 min. The sterilization rate was less affected by temperature and pH. We verified sulfate, hydroxyl and oxygen free radicals produced by the Pyr-SC-activated PS. The Pyr-SC composite, thanks to its expedited electron transfer, could activate PS to engender free radicals. Furthermore, the oscillatory transformation of iron ions caused by the monosulfide ion on the Pyr-SC surface augmented the production of free radicals. An assessment of Pyr-SC's stability was conducted, adhering to the principles of magnetic separation. After five cycles in the Pyr-SC/PS reaction system, the sterilization rate reached 3.29 lg, whereas the leaching rate of iron in Pyr-SC decreased. The Pyr-SC/PS reaction system also had a broad spectrum of wastewater. CONCLUSION The economically prepared Pyr-SC composite provided an effective technology for activating PS and sterilizing microorganisms in wastewater. © 2023 Society of Chemical Industry.
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