Research On The Controllable Synthesis,surface Modification And Adsorption Properties Of Actived Boron Nitride

Active porous boron nitride（BN）has the characteristics of abundant functional groups,large specific surface area,light weight,no pollution,non-toxic high temperature acid and alkali resistance,etc.The direction of new energy has important research value,but the unknown synthesis mechanism and the inability to industrialize mass production seriously limit its development.In this thesis,various testing methods were used to explore the formation mechanism of activated boron nitride;for the first time,thiol-modified activated porous BN was proposed;the mechanism of its surface loading was theoretically studied.On this basis,the pollutant adsorption capacity of boron nitride-based materials was evaluated.The main contents of this paper are as follows:（1）Using melamine diboronic acid（M2B）as the raw material of BN precursor,a series of actived porous BN fibers at different temperatures were prepared by pyrolysis method.The reaction mechanism was explored by X-ray diffraction,infrared thermal recombination and other methods,and finally the structural evolution mechanism of M2B to BN transition was deduced from the molecular scale.The research shows that the whole transformation process includes four main stages of boron oxide network formation and intercalation,melamine cross-linking,triazine ring decomposition,ammoniation evolution into BN structure,and the formation of porous structure with the generation of a large amount of gas.The specific surface area of the synthesized actived BN is as high as 1425 m² g^-1.Then,through the pollutant adsorption experiment of the dye,it was found that it has excellent adsorption performance for methylene blue,and quickly captures the dye molecules within 60 min.The pseudo-second-order kinetic model shows that its effect on dye molecules is chemical adsorption,and the isotherm fitting conforms to the Tempkin model.It has the characteristics of multi-layer and multi-site adsorption,and the maximum adsorption capacity can reach 623.7 mg g^-1.In addition,the adsorption capacities of methyl orange,Congo red,and rhodamine B can reach 197.4,184.5,48.3 mg g^-1,and also show affinity in the dynamic contact angle of chloroform.Oil and other properties,these properties make the actived porous BN can be used as a multifunctional static adsorbent.（2）Using mercaptopropionic acid as an activator for surface modification of actived BN,the adsorption capacity of heavy metal ions was improved by grafting organic functional group sulfhydryl groups.The binding mode of sulfhydryl groups on the surface of BN was explored by infrared,photoelectron spectroscopy and other methods.The results showed that the covalent bond of B-O-SH was formed on the surface and uniformly distributed on the actived BN.The pH,different adsorbent qualities,adsorption kinetics,thermodynamics,isotherms and other adsorption experiments were studied,and it was found that the thiol-modified actived BN had a very high adsorption capacity for mercury ions.An exploration of the adsorption mechanism suggested four possible interactions,including surface complexation of thiols and Hg²⁺,co-chelation of amino groups and thiol groups,ion exchange of various functional groups with oxyanions,and electrostatic interactions.Further experiments show that the wastes adsorbed by Hg²⁺can be used as catalysts for the conversion of phenylacetylene to acetophenone.DFT calculations indicated that the adsorption of mercury ions on the thiol-modified actived BN was due to the exchange mechanism of sulfur atoms and the double-defect structure.