The Performance And Mechanism Of Nitrogen Doped Carbon Nanotubes Coated With Cobalt Based Catalyst Activation Of Na₂SO₃ Degradation Of Organic Pollutants

In recent years,advanced oxidation of persulfate oxidation technology as an effective method of degradation of organic pollutants.However,because persulfates are too expensive,it is imperative to find alternatives to them.Sulfite is a commonly used reducing substance,inexpensive and readily available.Since transition metal ions can catalyze sulfite oxidation to generate active species such as sulfate radical(SO₄^·-)and hydroxyl radical?OH·?,the system is expected to be applied as a new advanced oxidation technology to the degradation of wastewater organic matter.According to cobalt metal ions and sulfite reactions,strong oxidative free radical SO₄^·-,OH·removal of organic pollutants,In this thesis,a high-temperature pyrolysis method was used to prepare carbon-doped cobalt-based catalysts doped with nitrogen,and its performance and structure were tested.To find an efficient,green and cheap non-homogeneous catalyst to explore the mechanism of the reaction,and to provide new ideas for the removal of organic pollutants by this new advanced oxidation technology.?1?The activation of sulfite by heterogeneous catalysts displays a great potential in the development of new sulfate radials based technologies for wastewater treatment.Thispaperstartswithmelamineandcobaltsalts,cobalt nanoparticlesembedded in N-doped carbon nanotubes?Co@NC?were prepared by a simple pyrolysis method.Due to the synergistic effects of the cobalt nanoparticles and N-doped carbon nanotubes,it can accelerate the catalytic oxidation of methyl orange?MO?in the presence of sulfite and molecular oxygen.A controlled trial using Co@NC revealed that about 35 percent of the MO could be absorbed by the catalyst within 20 minutes.However,the simultaneous presence of Co@NC and sulfite led to a significant increase in the removal efficiency of MO and 96%after 20 min.After four cycles?96%to 86%?,the performance only declined slightly,showing significant efficiency,excellent reusability and high stability.The structure and efficiency of the catalyst was also significantlyaffected by the content of cobalt and pyrolysis temperature.The effect of different anions,bicarbonate concentration,initial solution pH and dye types on the performance of the catalyst was also studied.Several quenching experiments and electron paramagnetic resonance were carried out to investigate the catalytic mechanism.It is found that hydroxyl and sulfate radicals worked together to degrade MO in the system.The formation and decomposition of peroxymonosulfate may be an important route of these reactive radicals production.?2?In this paper,cobalt salt,triethylenediamine,terephthalic acid and N,N-dimethylformamide as raw materials,the hydrothermal method to prepare a Co-MOF material,and then the product was subjected to thermal polycondensation to obtain the desired catalyst?Co@NC?.Through a series of characterization,it is found that the active components in the catalyst mainly exist in the form of zero-valent cobalt and oxidized cobalt,and the doping of nitrogen plays a very important role in the structural stability.According to the control test of Co@NC+HCO₃^-,about 40%of MO can be adsorbed by catalyst in 30 minutes,and the removal rate of MO was 93%after 30 min with Co@NC+HCO₃^-+SO₃^2-system.After five cycles?93%to 88%?,performance only declined slightly.In addition,For other organic pollutant degradation using Co@NC+HCO₃^-+SO₃^2-system,the removal rate of acid orange 7,reactive brilliant red,reactive brilliant blue and methylene blue was found to be 89%,96%,94%and 87%respectively after 30 minutes.A series of performance tests also show that its excellent performance and excellent stability,there is great potential for industrial applications.