Highly-efficient degradation of organic pollutants by oxalic acid modified sludge biochar: Mechanism and pathways.

The application of sludge biochar (SC) materials as efficient catalysts for organic pollutants mineralization via advanced oxidation process meets the good strategy of "make waste profitable". The catalytic oxidations of methyl orange (MO) and pyrene by oxalic acid modified sludge biochar (SC-OA) with and without H ₂ O ₂ were carried out. The analysis of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance spectrometer (EPR) and free radical quenching experiment were performed and the definite relationships between persistent free radicals (PFRs) type and specific reactive oxygen species (ROS) were made clear. It is suggested for the first time that carbon-centered type PFRs in SC-OA without H ₂ O ₂ could form O ₂ • ^- and •OH from COOH groups, while oxygen-centered type PFRs induced H ₂ O ₂ to produce •OH. The degradation intermediates of MO and pyrene were identified and the transformation pathways were proposed. SC-OA, possessing good sustainable utilization and clean catalytic property, is expected to be popularized and applied in the mineralization of organic pollutants, especially in the in-situ remediation of contaminated soil where is no continuous supply of H ₂ O ₂ .
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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