Highly efficient catalysts of phytic acid-derivative cobalt phosphide encapsulated in N, P-codoped carbon for activation of peroxymonosulfate in norfloxacin degradation

Abstract

We synthesized CoP2 encapsulated in N, P-codoped carbon (CoP2@NPC) hybrids derived from phytic acid cross-linked cobalt and melamine complexes. The composites were tested as heterogeneous catalysts to activate peroxymonosulfate (PMS) in the degradation of norfloxacin (NOR). The 93% of 40-μM NOR was degraded within 10 min at pH 7.5 using 0.1 g L−1 CoP2@NPC and 1-mM PMS. The CoP2@NPC suffers little interference from existing Cl− and humic acid (HA) but is hampered by HCO. Radical quenching experiments and electron paramagnetic resonance (EPR) results confirm that PMS can be activated by CoP2@NPC to produce SO4−·, HO·, and 1O2. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal that Co(II) and phosphorus-neighboring carbon in CoP2@NPC tends to transfer electrons to chemisorbed PMS and generate free radicals, but nitrogen-neighboring carbon captures electrons from PMS to produce 1O2.