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

Abstract

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 SO₄•¯, •OH and •O₂¯ without singlet oxygen. The synergistic effect of radical and nonradical pathways played crucial roles during the SCP oxidation process.