Rationally Synthesis Of MnO₂-based Hybrids With Enhanced Catalytic Performance For Wastewater Treatment

With the high-speed development of human society,it inevitably emits a variety of pollutants in the process of production and life,including dyeing and printing wastewater.It has deep color,serious toxicity and poor biodegradability,so its decolouration and mineralization have become a big problem for dyeing wastewater treatment.In recent years,advanced oxidation processes?AOPs?based on the catalytic wet peroxide oxidation?CWPO?were proved to be an effective method for the removal or degradation of recalcitrant dyeing wastewater.The key to achieve industrial application of AOPs highly lies in the development of efficient and stable catalysts and their recyclable technology.Manganese dioxide is the most common catalyst used in method of wet hydrogen peroxide,but the manganese dioxide from the coverage has some disadvantages,including small specific surface area,low catalytic efficiency,poor recovery and so on.Therefore,in this paper the rapid degradation of printing and dyeing wastewater is seen as a purpose,and the design of high efficient catalyst as the breakthrough point,finally manganese dioxide and its compounds are prepared to achieve the goal of improving the efficiency of degradation and the catalyst recycling.The detailed studies are as follows:?1?At first,we have prepared four different manganese dioxide?MnO₂?materials?named as S-1,S-2,S-3,and S-4?by different methods.X-ray diffraction?XRD?,fourier transform infrared?FTIR?spectroscopy,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,the automatic surface area and pore size analyzer?BET?and other technical means were applied to investigate the composition and microstructure of the produced materials.Combined with the studies of catalytic performance,it shows that sample S-3 has the best adsorption and catalytic performances.The degradation rate of methylene blue?MB?can get as high as 96.3%.At the same time we also examined how the factors of the temperature,p H and the content of H₂O₂ affect the catalysis performance.The results showed that the dosing of H₂O₂ is the primary factor affecting the efficiency to remove MB from dye solution,followed by pH,temperature and other factors.In addition,the recycle of catalyst is good and it has the favorable stability.?2?Secondly,we synthesized different MnO₂/SnO₂ composites based on manganese dioxide?S-4?.We found that when the ratio of tin and manganese is 4,it has the better microstructure by X-ray diffraction?XRD?,Fourier infrared absorption analyzer?FTIR?,scanning electron microscope?SEM?and transmission electron microscope?TEM?.Then we compared adsorption and catalytic properties of prestine MnO₂ and MnO₂/Sn O₂ composites;and found that MnO₂/SnO₂ composites had better catalytic performance.The degradation rate of MB can get 92.4%,5.7%higher than the prestine MnO₂.?3?Finally,we synthesized ferriferous oxide?Fe₃O₄?nanoparticles?FNs?and nanosphere?FHs?with different morphology;and load different mole ratios of thin layered MnO₂ to the surface of Fe₃O₄.Susquently,we made six coposites in total.We analyzed their microstructures by X-ray diffraction?XRD?,Fourier infrared absorption analyzer?FTIR?and transmission electron microscope?TEM?,and studied the catalytic degradation experiment.As a result,degradation efficiency of the composties were significantly enhanced compared to prestine substances.However,as further increasing the amount of MnO₂,the performance of the composite does not increase gradually but decrease instead.It got the best when the MnO₂ mole ratio is0.2,and catalytic degradation rate is up to 95.7%.