Synergistic effects of Co and N doped on graphitic carbon as an in situ surface-bound radical generation for the rapid degradation of emerging contaminants

Abstract

• Co-anchored on N doped graphitized carbon material (Gc-N-Co) was prepared. • Gc-N-Co has a higher CIP degradation and PMS decomposition. • Co-ordination of the pyridinic N and Co was a predominant factor. • Surface-bound (SO 4 •− ) radical was the dominant mechanism. • The influence of pH, temperature, and background ions was observed. Co-anchored on N doped graphitized carbon material (Gc-N-Co) was synthesized using glucose and melamine as carbon and nitrogen source, respectively. The prepared Gc-N-Co demonstrate a higher removal efficiency and PMS (peroxymonosulfate) decomposition compared to other control catalyst of Gc-N and Gc-Co, implying a synergistic effect between the precursor materials. The high performance was attributed to the co-ordination between the pyridinic N and Co forming N-Co bonds on the catalyst surface capable of degrading a wide range of organic contaminants (ciprofloxacin, carbamazepine, sulfamethoxazole, and 4-chlorophenol). Surface-bound (SO 4 •− ) radical was established as the dominant mechanism of the reaction process based on the quenching experiments and EPR tests. The activation energy (E a ) of 26.4 kJ/mol further established that an intrinsic chemical reaction takes place on the catalyst surface rather than in solution. Also, the electrostatic attraction observed at neutral pH validates the surface interaction between the surface-bound SO 4 •- radical and the organic molecules. The negative influence of inorganic ions followed the order of SO 4 2- > Cl - > NO 3 - , and the positive effect of HCO 3 – was discussed. In addition, Gc-N-Co demonstrate excellent reusability in four consecutive cycles consolidating on the presence of the strong N-Co bonds.