Neglected but Efficient Electron Utilization Driven by Biochar-Coactivated Phenols and Peroxydisulfate: Polyphenol Accumulation Rather than Mineralization
journal contributionposted on 2023-03-18, 13:03 authored by Jibo Dou, Yao Tang, Zhijiang Lu, Guangzhi He, Jianming Xu, Yan He
We report an unrecognized but efficient nonradical mechanism in biochar-activated peroxydisulfate (PDS) systems. Combining a newly developed fluorescence trapper of reactive oxygen species with steady-state concentration calculations, we showed that raising pyrolysis temperatures of biochar (BC) from 400 to 800 °C remarkably enhanced trichlorophenol degradation but inhibited the catalytic production of radicals (SO4•– and •OH) in water and soil, thereby switching a radical-based activation into an electron-transfer-dominated nonradical pathway (contribution increased from 12.9 to 76.9%). Distinct from previously reported PDS* complex-determined oxidation, in situ Raman and electrochemical results of this study demonstrated that the simultaneous activation of phenols and PDS on the biochar surface triggers the potential difference-driven electron transfer. The formed phenoxy radicals subsequently undergo coupling and polymerization reactions to generate dimeric and oligomeric intermediates, which are eventually accumulated on the biochar surface and removed. Such a unique nonmineralizing oxidation achieved an ultrahigh electron utilization efficiency (ephenols/ePDS) of 182%. Through biochar molecular modeling and theoretical calculations, we highlighted the critical role of graphitic domains rather than redox-active moieties in lowering band-gap energy to facilitate electron transfer. Our work provides insights into outstanding contradictions and controversies related to nonradical oxidation and inspiration for more oxidant-saving remediation technologies.
Read the peer-reviewed publication
work provides insightssup >•</ supsaving remediation technologiesreactive oxygen speciesraising pyrolysis temperaturespolyphenol accumulation rathergraphitic domains ratherefficient nonradical mechanismdominated nonradical pathwaystate concentration calculationsbiochar molecular modelingpreviously reported pdsbiochar surface triggersfacilitate electron transferdriven electron transferbiochar surfacenonradical oxidationtheoretical calculationsthereby switchingstudy demonstratedsitu </simultaneous activationpotential differencepolymerization reactionsoutstanding contradictionsoligomeric intermediateslowering bandgenerate dimericgap energyeventually accumulatedelectrochemical resultse </determined oxidationcritical rolecontroversies relatedcontribution increasedcatalytic productionbased activationactive moieties182 %.