Arsenite (As(III)) oxidation has been deemed as the prerequisite for the efficient removal of arsenic in groundwater. Pyrogenic carbon can mediate As(III) oxidation and shows great potential in tackling this challenge. Herein, the critical role of N-containing functional groups in low and high temperature prepared pyrogenic carbons for mediating As(III) oxidation were systemically explored from an electrochemistry perspective. The pyrogenic carbon electron donating capacity and area-normalized specific capacitance were the key parameters explained the As(III) oxidation kinetics mediated by low electrical conductive 500oC biomass-derived pyrogenic carbons (R2 = 0.87, p &lt; 0.001) and high electrical conductive 800oC N-doped pyrogenic carbons (R2 = 0.99, p &lt; 0.001), respectively. The production of H2O2 from the reaction between electron donating phenol groups or semiquinone radicals and oxygen, and the direct electron transfer between semiquinone radicals and As(III) were contributed to these pyrogenic carbons mediated As(III) oxidation. The reduction of electron accepting quinone groups to phenol groups and semiquinoneradicals could regenerate the As(III) oxidation capacity for all these pyrogenic carbons. While the electron accepting quinone, pyridinic-N, and pyrrolic-N groups did not significantly contribute to the 500oC pyrogenic carbons mediated As(III) oxidation, the direct electron conduction by these functional groups were responsible for the facilitated As(III) oxidation by the 800oC pyrogenic carbons. Furthermore, the pyridinic-N and pyrrolic-N groups showed higher electron conduction efficiency than that of quinone groups. The elucidation of the role of specific oxygen- and nitrogen-containing functional groups and electrical conductivity in mediating As(III) oxidation at alkaline environment enables developing robust pyrogenic carbons for As(III) contaminated groundwater treatment.

Linking pyrogenic carbon redox property to arsenite oxidation: Impact of N-doping and pyrolysis temperature

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