Catalytic Oxidation Properties Of Nonmetallic Doped Carbon Nanotubes Coated With Magnetic Metal Nanoparticles

Based on the strong biological toxicity and poor biodegradation of persistent organic pollutants, the magnetic metal M (M=Fe,Co, Ni) nanocrystals encapsulated in nitrogen-doped carbon nanotubes (CNTs) and iron nanoparticles (NPs) embedded in B,N-codoped CNTs as heterogeneous Fenton-like catalysts were obtained by a simple and scalable pyrolysis method. And their performances were investigated in the oxidative degradation of Orange ?. In this study, a novel catalytic oxidation reaction system based on SO4·- radicals was constructed, and M@N-C/PMS, Fe@C-BN/PMS systems were analyzed in detail from the view of degradation kinetics, influenced factors and catalytic mechanism. Combined with the XRD, XPS, SEM and TEM techniques, the structure activity relationship among the composition, structure and catalytic performance were further clarified. The following studies were carried out:(1) M@N-C catalysts were prepared by pyrolysis method and were successfully applied to activate peroxymonosulfate (PMS) for removal of organic contaminants. The catalysts exhibited tubular structures, and the metal NPs were effectively coated by CNTs to form a core-shell structure. The degradation efficiency of Orange II induced by M@N-C/PMS system abided by the order of Co@N-C > Fe@N-C > Ni@N-C. And the effects of several operational factors, such as reaction temperature, PMS dosage as well as initial dye concentration were extensively evaluated using Co@N-C/PMS as the model system. In addition, the cycle experiments revealed that the catalyst had excellent stability and recyclability. Moreover, SO4·- and ·OH radicals participating in the process were evidenced using quenching experiments, and control experiments showed that the enhanced active sites of M@N-C were mainly ascribed to the synergistic effects between the metal NPs and nitrogen-doped carbon nanotubes.(2) Fe@C-BN catalysts were fabricated conveniently using boric acid, melamine and iron nitrate nonahydrate as raw material, and the as-prepared catalysts were denoted as Fe@C-BNTX (where T represents the calcination temperature and X represents the initial mass of iron salts). The characterization results showed that the catalysts consist of bubble-chain nanotubes encapsulated with iron nanoparticles, and that both nitrogen and boron species are homogeneously distributed throughout the whole structure. The catalytic experiments revealed that Fe@C-BN8006/PMS system had the best removal efficiency, which indicated that the various synthesis temperature and the dosage of iron salts had different impact on the activation of PMS. Therefore, the effects of several reaction conditions, such as initial pH, inorganic anions, reaction temperature as well as dye types were investigated using Fe@C-BN8006 /PMS system. Through the investigation of reaction processes, it is concluded that the synergistic effects between iron NPs and B,N-codoped CNTs can catalyze the PMS to generate SO4·- and ·OH radicals for organic pollutants' purification.