New magnetic carbon beads doped with graphene and cobalt to efficiently degrade sulfamethoxazole: superoxide radical acceleration strategy

Metal leaching will lead to serious deactivation of powder metal catalysts and environmental pollution, which restricts the further practical application of metal catalysts. In the present work, long lifespan millimeter-scale composite carbon beads (CoNC@cPAN/rGO-800), which were prepared by using 2-methylimidazole cobalt (ZIF-67), polyacrylonitrile (PAN) and graphene oxide (GO) as raw materials, perform well in addressing the issues of metal catalyst deactivation and pollution in activating peroxymonosulfate (PMS) for the oxidative degradation of sulfamethoxazole (SMX). This catalyst achieved 100% removal efficiency within 20 min and exhibited a wider pH range of applicability. Furthermore, the specific contribution of superoxide radicals (O 2 ·− ) in AOPs has been elucidated. It is revealed that the catalytic oxidation mechanism by CoNC@cPAN/rGO-800 involves two phases: direct activation of PMS into SO 4 ·− , ·OH and 1 O 2 by cobalt active sites; indirect activation, wherein O 2 − is derived from an oxygen molecule via oxygen vacancy (O v ) and then turns into 1 O 2 or subsequently activates PMS into SO 4 ·− and ·OH, thereby generating more active species and potentially contributing to SMX degradation. Moreover, the doped reduced GO can lower the electronic impedance to enhance inside-out electron transfer of carbon beads and promote the generation of O v in the nuclei of carbon beads. Compared with traditional powder catalysts, the new carbon beads exhibit distinct advantages: excellent catalytic performance, easy recyclability, and high stability.