Nonradical Degradation of Microorganic Pollutants by Magnetic N-Doped Graphitic Carbon: A Complement to the Unactivated Peroxymonosulfate

Abstract

N-doped carbonaceous materials are highly promising for efficient removal of microorganic contaminants from aqueous solutions by simultaneously serving as adsorbents and catalysts. However, their recollection from aqueous solutions for repeated use is challenging. Here, we designed a magnetic N-doped graphitic carbon core–shell structure (MN-GCCS) for oxidative degradation of various microorganic contaminants via the activation of environmentally friendly peroxymonosulfate (PMS). The magnetic Co3O4 core ensured the easily recollection of MN-GCCS via magnetic separation. Meanwhile, the graphitic carbon ideally prevented the Co3O4 from leaching. MN-GCCS showed great reactivity for pollutant degradation at a wide range of pH values and was particularly active under circumneutral conditions (pH 6–8). MN-GCCS outperformed the commonly known activators of PMS; Under identical conditions, near 100% of atrazine was removed with MN-GCCS, while only 36%, 21%, and 14% of the atrazine were removed with multi-walled carbon nanotubes, CuFe2O4, and Co3O4, respectively. In contrast to the known radical processes, the degradation of contaminants by MN-GCCS–PMS was not mediated by radicals. Instead, a mechanism involving a transition oxidation state of MN-GCCS as the major oxidizing intermediate was proposed. The results from this study suggest a novel and highly efficient nonradical process for oxidative degradation of organic contaminants.