Electron Transfer Tuning for Persulfate Activation Via the Radical and Non-Radical Pathways with Biochar Mediator

Abstract

Electron mediator-based in-situ chemical oxidation (ISCO) offers a novel strategy for groundwater remediation due to diverse reaction pathways. However, distinguishing and further tuning the reaction pathway remain challenging. Herein, biochar as electron mediator were utilized to targeted active peroxysulphate (PDS) via radical or non-radical pathway. Exemplified by the triazin pesticides removal, the complex radical (•OH and SO4•-) and non-radical active species (electron transfer oxidation) were generated and identified in different biochar/PDS systems. The electron transfer process between biochar and PDS were significantly distinguished via an innovatively in situ visualization of radical pathway, and the electron transfer oxidation non-radical pathway is directly unveiled via a galvanic cell experiment combined with LC-MS analyses. The electron transfer mechanism was revealed via established the quantitative structure-activity relationships between biochar and ln kobs. The redox capacity of biochar was assessed as a key for tuning the atrazine degradation by non-radical pathway, the surface carbon-centered persistent free radicals (PFRs) were identified as key electron donors for triggering the radical pathway. This study gives new insights into the explore the electron transfer mechanism during tuning radical and non-radical activation pathway and further improve the utilization of oxidants in ISCO.

Keywords: Groundwater Contamination, Electron Mediator, Activation Pathway, Electron Transfer Tuning, Radical Visualization