Study On The Preparation Of Mesoporous Carbon-loaded Cobalt Catalysts And The Catalytic Degradation Of Organic Wastewater By Oxone

Advanced oxidation processes?AOPs?have the attributes of high efficiency,universality,andthoroughness in the treatment of refractory organic matter,and has become a hot research topic in the field of refractory wastewater treatment.Highly active free radicals in the system,such as hydroxyl radicals?·OH?and sulfate radicals(SO₄^·-),oxidize and decompose organic pollutants into CO₂,H₂O,and inorganic salts.Compared with the Fenton system which produces·OH radicals,the SO₄^·-oxidation system is more adaptable to water quality conditions and no sludge is generated.Therefore,it is an important subject in the field of water treatment at home and abroad to prepare a catalyst with high efficiency and insolubility to form a new oxidation system with Oxone.In this study,mesoporous carbon-loaded cobalt materials?Co-MC?and magnetic mesoporous carbon-loaded cobalt materials?Co-MMC?were prepared by hydrothermal method and carbonization reaction.Co-MC@Bi₂WO₆ composites were prepared by hydrothermal loading of Bi₂WO₆ nanosheets.The crystal form,microstructure,composition,element valence,functional group composition,band structure of the catalysts were measured by characterization of X-ray diffraction analysis?XRD?,transmission electron microscopy?HRTEM?,specific surface area?BET?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?and so on.The activity of the catalyst was evaluated by degrading the target pollutants Rhodamine B?RhB?or levofloxacin hydrochloride?LVF?under natural sunlight.This study provides a theoretical basis for the application of mesoporous carbon-loaded cobalt composite catalysts in the development and treatment of organic wastewater.The main research contents and conclusions are as follows:?1?Preparation of Co-MC catalysts and the degradation of RhB by Co-MC/Oxone oxidation system:Different ratios of mesoporous carbon-loaded cobalt materials were prepared by hydrothermal reaction of different masses of cobalt sulfate with mesoporous carbon.The study determined that the optimum catalytic loading ratio was 3:1,and then characterized the XRD,SEM,EDS,BET and XPS of 3:1 Co-MC.It can be seen from the characterization results that the prepared 3:1 Co-MC has a lower degree of graphitization and an amorphous state of the entire carbon framework,and Co?II?becomes Co?III?during carbonization.Its morphology is composed of a number of spherical particles agglomerated to form a long strip shape,the composition of which is mainly C,O,Co.By studying the catalytic activity and properties of Co-MC materials,it can be seen that the rhodamine B solution can be completely degraded within 8 min when the loading ratio was 3:1.Therefore,Co-MC had the good catalytic activity of Oxone on degradation of rhodamine B.?2?Preparation of Co-MMC catalysts and the degradation of LVF by Co-MMC/Oxone oxidation system:Under the premise of hydrothermal preparation of Co₃O₄ solids,magnetic mesoporous carbon-loaded cobalt?Co-MMC?catalysts were synthesized by hydrothermal and carbonization reactions.The catalytic activity was preferably Co-MMC with a cobalt content of 5.2%.Then the results of LVF degradation experiments showed that the optimal experimental conditions were 14 mmol/L Oxone and 25 mg 5.2%Co-MMC.The initial pH of the solution was 7,the reaction temperature was 25°C,and the degradation efficiency was about 98%within 40 min.The TOC removal rate of LVF in 40 min was 65.86%.The comparison of degradation efficiency indicated that LVF produced intermediate products during the experiment.The experimental data of five consecutive cycles showed that the degradation rate of LVF decreased successively,indicating that the recyclability of the catalyst was not so good,which may be related to the large amount of Co ion elution.Free radical quenching experiments show that SO₄^·-has a great influence on the degradation of LVF.?3?Preparation of Co-MC@Bi₂WO₆ catalysts and the degradation of LVF by Co-MC@Bi₂WO₆/Oxone oxidation system:Co-MC@Bi₂WO₆ composite catalyst was prepared by hydrothermal method.The experimental results showed that the best catalytic activity under natural sunlight was Co-MC@Bi₂WO₆ with a mass ratio of 3:1:3.In the LVF degradation experiment,the best experimental conditions were under natural sunlight,25mg 3:1:3 Co-MC@Bi₂WO₆,14mmol/L Oxone,initial solution pH=7,25°C reaction temperature,and the optimal degradation efficiency could reach 98%in 40min.The Co-MC@Bi₂WO₆ materials had good stability and reusability through five consecutive cycles of reaction experiments.The free radical quenching experiment proved that the combination of·OH produced by photocatalysis and SO₄^·-produced by advanced oxidation technology caused the target to be oxidatively decomposed and completed the degradation of organic wastewater.