Electrically driven enhancement on selective adsorption of nitrate by microporous carbon from wastewater: Synergism of functional groups and micropores

[Display omitted] •A series of carbon materials with different functional groups and pore structures were fabricated.•The effects of pore sizes, functional groups, and applied voltage on nitrate selective removal were systematically investigated.•The increase of voltage enhances interfacial electron transport and nitrate mass transfer.•Functional groups drive microporous ion sieving through electrostatic interaction to improve nitrate removal selectivity. In the presence of coexisting ions, the limited selectivity hampers the application of NO3– adsorption. Herein, a series of NO3– adsorbents featuring adjustable degrees of functional groups and pore structures were synthesized to explore their structure–activity relationship at atomic level. The effects of pore sizes, functional groups, and applied voltage on the selective removal of NO3– were systematically investigated. Theoretical calculations and experiments confirmed that pore sieving effect and electrostatic attraction provided by functional groups synergically enhance NO3– selectivity. The applied voltage changes the interfacial microenvironment of adsorbent and improves the interfacial electron transmission, thus promoting NO3– transfer and enrichment on adsorbent surface. Meanwhile, increasing electrostatic attraction can not only increase the adsorption capacity but also improve the selective screening of anions by micropores. Driven by an external voltage of 1.2 V, NO3– selectivity of ZIF-8-C-Q-2 nearly doubles. Under higher voltage, ZIF-8-C-Q-2 exhibits lower charge transfer resistance and higher ion diffusion capacity, which is conducive to capturing electrolyte ions (NO3–), thereby enhancing its adsorption capacity and selectivity. This study provides a novel insight into synergism of functional groups and micropores for selective adsorption of NO3– in electrosorption mode.