Heteropoly Acid Modified Magnetic Chitosan And Its Adsorption Investigation For Methylene Blue

Keggin-type heteropolyacids have extremely strong protonic acidity,large anion volume,higher symmetry,lower charge density,and greater proton mobility,making protons in the molecule very easy to dissociate,Therefore,it is more acidic than traditional inorganic oxyacids.However,due to its relatively small surface area,the entry of active sites is hindered.Moreover,the high solubility in aqueous solutions is inconvenient for recycling and reuse,resulting in limited application.However,due to its relatively small surface area,the entry of active sites is hindered.Moreover,the high solubility in aqueous solutions is inconvenient for recycling and reuse,resulting in limited application.In this paper,Fe₃O₄ particles were used as magnetic nuclei,chitosan was used to modify its surface,cross-linked by glutaraldehyde,Chitosan and glutaraldehyde form a network polymer layer on the surface of Fe₃O₄ particles,and they are modified with heteropolyacids as adsorbents to adsorb methylene blue.In the first chapter,an overview of polyoxometallates is presented,and its classification,application,and characteristics of Keggin-type heteropolyacids are described.Then,the dye wastewater treatment method,research status and the basic theory of adsorption and the application of polyoxometallate as adsorbent material in the field of wastewater treatment are described.Finally,the background and main work of this paper are clarified.In the second part of the experiment,the instruments and reagents used in the experiment were listed.Finally,the characterization method and the calculation method of adsorption and the preparation and determination of methylene blue were introduced.In the third,fourth and fifth chapters,phosphotungstic acid,phosphomolybdic acid and silicotungstic acid were used as raw materials to synthesize composites Fe₃O₄/CSGA-PTA,Fe₃O₄/CSGA-PMA and Fe₃O₄/CSGA-STA in a one-pot process.They were characterized by X-ray powder diffraction?XRD?,thermogravimetric analysis?TGA?,infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,nitrogen adsorption-desorption?BET?,and their use adsorpt.The results show that these composites have good adsorption effect,can be used repeatedly and can form a uniform dispersion suspension in the methylene blue solution.When the adsorption is completed,the adsorbent can be separated from the solution by an external magnetic field.