Preparation Of Nanoscale Catalyst MnO₂ By Microwave Plasma In Liquid

The development period of microwave discharge in liquid technology is short.Th-ere are only a few scholars and experts who have studied on it.Microwave discharge in liquid produces a higher plasma density in the solution and a large number of active par-ticles such as:OH radicals,O radicals,H radicals and other particles.These active parti-cles have a high redox potential,especially OH radicals which can be as high as 2.8 eV,furthermore,it has been applied in the field of advanced oxidation.At the same time,the high-energy electrons,radicals and other particles released in microwave discharge in liquid can react with the liquid medium to synthesize new substances.This is also the current field of liquid discharge research direction.The success of the microwave discharge in liquid depends on the discharge electro-de and feeder matching.For the feeder which has fixed structure and material,the electrode structure and material are particularly significant.In this paper,a new material electrode is selected based on the standing wave ratio(SWR),which reflect the matching situation.Compared with the old material electrode,the firing time of the new material electrode is greatly prolonged.And the new material electrode will not cause the problems that amount of Joule heat produced by the electrode tip in the process of the discharge which results in the silica gel dissolved and the solution contaminated.The effects of temperature,pH,conductivity,dielectric constant and pressure in the reaction chamber on the matching effect were analyzed.In this paper,the reduction of microwave liquid discharge is used to reduce potass-ium permanganate to manganese dioxide under certain conditions.The solution after the reaction was analyzed by ultraviolet-uisible spectrophotometer(UV-vis)and emission spectrum(OES).The black powder was extracted from the treated solution and charact-erized by X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),transmis-sion electron microscopy(TEM),UV-visible diffuse reflectance spectroscopy(DRUV-S).The results show that this method has synthesized nanoscale layered manganese dioxide(?-MnO2),what is more,the synthetic pathway and mechanism are deduced.The surface particles of layered manganese dioxide(?-MnO2)are not only small but also have the low degree of crystallization,the large specific surface area,the large chemical activity and the strong oxidative adsorption capacity.They are often used as water purification materials for wastewater treatment including heavy metal adsorption,the oxidative degradation of organic pollutants of wastewater and so on.In this paper,we use the methylene blue as a simulated organic pollutants and the high pressure mercury lamp as an ultraviolet light source to research the degradation of organic wastewater with the synthetic manganese dioxide as the catalytic Oxidation reagent.