The Removal Performance Of Organic Pollutants From Water By Oxygen-Rich Vacancy Magnesium-Based Materials

With the rapid development of industries,such as papermaking,textile,leather,plastics,printing,and cosmetics,a large amount of wastewater generates many toxic substances through oxidation and hydrolysis chemical reactions.It has caused serious environmental pollution,and the removal of organic wastewater is requested to be solved urgently.Among the treatment methods,adsorption and photocatalysis are widely used because of their simple operation,rapid speed,and high efficiency.Magnesium oxide（MgO）is a promising material to remove organic dyes by adsorption and photocatalysis due to its non-toxicity,abundant oxygen vacancies,and chemical stability.However,as an adsorbent,the adsorption capacity of MgO needs to be improved,and as a photocatalyst,its wide bandgap of MgO is difficult to be excited by visible light.Here,the surface and bandgap properties of MgO are improved by controlling the concentration of oxygen vacancy to enhance the adsorption and photocatalytic performance of organic substances.The main research contents are as follows:（1）High-temperature reduction is a common method to generate oxygen vacancy.MgO with abound oxygen vacancy was synthesized by co-precipitation and hydrogen high-temperature reduction methods.The effects of calcination temperature on the crystal structure,surface morphology,and surface properties of MgO were investigated.It was found that the MgO obtained at 600℃showed high adsorption properties due to its rich oxygen vacancies.The maximum adsorption capacity of reactive blue 19（RB19）was 578.03 mg g^-1.In addition,the important role of the appropriate specific surface area and oxygen vacancy content in enhancing the adsorption performance was detected.The mechanism of the electrostatic adsorption of RB19 molecules by MgO was proposed.（2）The Cu-MgO photocatalysts were prepared by a photodeposition and high temperature reduction methods.The effect of Cu content on the photocatalytic degradation of Rhodamine B（Rh B）was studied.It was found that the photocatalytic degradation efficiency of 3%Cu-MgO was 92.8%of Rh B,which was 20%higher than that of MgO-600.The analysis of XPS and TEM presented that there were two existing states of Cu.One is doped with Cu²⁺into the MgO lattice,the other is loaded with Cu⁰on the MgO surface.Cu²⁺doping in MgO produced many oxygen vacancies,which induced a narrower bandgap and a wider range of light absorption.The Schottky barrier formed between Cu⁰and MgO effectively separated the photo-charges through one-way charge transfer,improving the photocatalytic performance.（3）Carbon microspheres（CMS）display the excellent ability of electron transfer,which can be the migration path of photogenerated electrons in a catalyst.Herein,the carbon microspheres were prepared by hydrothermal pyrolysis of glucose.And then the amorphous carbon microspheres/MgO composite catalysts（CMS/MgO）with oxygen-rich vacancies were prepared by a high-temperature calcination method.The MgO nanoparticles were uniformly distributed on the surface of carbon microspheres,effectively improving the specific surface area.The degradation rate of CMS/MgO reached 94.6%in 70 min,which was significantly higher than that of single-phase MgO（80.1%）.The improvement of photocatalytic activity can be ascribed to the combined effect of oxygen vacancies and amorphous carbon microspheres.Amorphous carbon microspheres provided a channel for rapid electron transfer.The oxygen vacancy in MgO both increased the active site and captured the electrons,resulting in an effectively promoting separation and transformation of charges.