Crucial role of nitrogen vacancies in carbon activated persulfate toward nonradical abatement of micropollutants from secondary effluent

Biomass-derived carbonaceous materials exhibit fascinating potentials in nonradical oxidation of micropollutants (MPs) by activating persulfate and their performances mainly rest on graphitic N. However, the simultaneously derived N vacancy received little attention. Herein, a graphene-like material rich in N vacancy was synthesized from coffee residues. It showed excellent removal efficiency (95 %) and degradation kinetics (0.21 min(-1)) in abating tetracycline antibiotics from secondary effluent and significant biotoxicity was diminished. Solid nonradical oxidation consisting of electron transfer (89 %) and singlet oxygen (O-1(2)) oxidation (11 %) was determined. By tracking O-1(2) source and electron flow, ketone group appeared at N vacancy was found as the critical site to grab electrons from peroxydisulfate (PDS) with production of O-1(2). Then the electrons were transferred to graphitic N driven by the microelectric field between them. This work notices the function of vacancies in biomass resources for high-efficient removal of MPs from real water matrix.