Nickel in hierarchically structured nitrogen-doped graphene for robust and promoted degradation of antibiotics

Nickel nanoparticles encapsulated in nitrogen-doped porous graphene (Ni@NPG) were synthesized through a one-pot method as a novel material for catalytic activation of persulfate (PS). The Ni@NPG catalysts were evaluated for adsorptive and catalytic removals of antibiotic sulfachloropyridazine (SCP) as an emerging pollutant and were found to exhibit excellent adsorption and catalysis with 100% SCP removal from water in only 30 min. Meanwhile, great stability and reusability can be achieved with satisfactory organic degradation after 4 successive runs. In addition, metal leaching was prohibited from the metal@carbon catalysts due to the protection of carbon walls. The influences of humid acid and inorganic anions (HCO3-, Cl-, Br- and H2PO4-) on SCP degradation at various concentrations were further investigated and the present study shows that all these species promoted the SCP degradation at a low concentration whereas an inhibition effect occurred at higher concentrations due to radical quenching. Electron paramagnetic resonance (EPR) and quenching experiments reveal the PS activation mechanism involving generation of SCO4 center dot-,(OH)-O-center dot and center dot O-2(-) without singlet oxygen. The synergistic effect of radical and nonradical pathways played crucial roles during the SCP oxidation process. (C) 2019 Elsevier Ltd. All rights reserved.