In-situ formed N-doped bamboo-like carbon nanotubes encapsulated with Fe nanoparticles supported by biochar as highly efficient catalyst for activation of persulfate (PS) toward degradation of organic pollutants

In this study, N-doped bamboo-like carbon nanotubes encapsulated with Fe nanoparticles (Fe NPs) on the surface of soybean dregs-derived biochar (Fe@NCNT - BC) was synthesized via a low-cost and facile strategy. The unique composites behaved as efficient catalysts for the degradation of various organic pollutants by the activation of persulfate (PS). Under the conditions of [PS] = 5 mM, [RhB] = 20 mg/L, [Fe@NCNT-BC-800] = 1.0 g/L, pH = 7.0, the RhB degradation rate was very fast reaching up to 100% within 10 min. The system also exhibited significant high activity in a broad pH window (3.0-11.0). Meanwhile, the recycling experiments and Fe leaching tests further demonstrated the stability of Fe@NCNT - BC during the activation of PS. Most interestingly, the Fe nanoparticles played a key role in promoting the degree of graphitization and the formation of bamboo-like N-doped carbon nanotubes. Besides, the introduction of biochar significantly improved the dispersion ability to the Fe@NCNT - BC. The competitive radical quenching tests and electron paramagnetic resonance measurements (ESR) illustrated that instead of the traditional radicals (sulfate radicals and hydroxyl radicals), the non-radical singlet oxygen (O-1(2)) was the dominant reactive oxidative species (ROS) in the Fe@NCNT-BC/PS system. A mechanistic study suggested that pyridinic N, graphitic N, sp(2)-hybridized carbon structure and C = O bond in the Fe@NCNT - BC - 800 promoted the generation of the ROS. This study successfully provides an economic and feasible method for synthesis of a novel catalyst as an eco-friendly and efficient material for the degradation of organic pollutants in the environment.