Co nanoparticles/N-doped carbon nanotubes hybrids as highly efficient catalysts for microwave-induced catalytic degradation of tetracycline

Large-scale magnetic Co nanoparticles/N-doped carbon nanotubes (Co@NCNTs) hybrids have been designed by pyrolyzing the mixture of cobalt nitrate and melamine for microwave (MW)-induced tetracycline (TC) degradation. The results demonstrated that Co@NCNTs-5, annealed from cobalt nitrate and melamine (mole ratio: 1:5), possessed a good MW absorption ability, resulting in excellent degradation performance towards TC. Specifically, 99.5 % TC (20 mg/L, natural pH) could be removed after 6 min of MW irradiation (520 W) in the presence of Co@NCNTs-5. Meanwhile, Co@NCNTs-5 exhibited competitive degradation efficiency over TC at various concentrations (20-100 mg/L) and pH values (3-8). Results of reusability experiments identified the magnetic recovery ability and stability of Co@NCNTs-5. Based on free radical experiments and electron paramagnetic resonance (EPR) results, HO•and O2-•radicals participated in the catalytic degradation process. The degradation pathway of TC was proposed with the assistance of ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS). This work develops a facile, low-cost and large-scale method to synthesize Co@NCNTs, which demonstrates great potential in MW-induced catalytic treatment of antibiotic pollutants as high-efficient catalysts.