Synthesis And Application Of Functional Porous Microspheres In Separation And Analysis

The control of morphology and porosity is important and also the most difficult in the synthesis of porous materials,which directly influences the application performance of the materials.Micropores and mesopores guarantee high surface area and abundant active sites;whereas,macropores accelerate mass transfer,and thus provide high permeability and low back pressure.Among the various porous materials,porous microspheres win great popularity in modern separation and analysis,which possess several superiorities including high surface area,favourable dispersibility,easy control of morphology and porosity,and convenient functionalization.Specifically,silica microsphere is still the most frequently-used chromatographic packing materials,but its applicational performance deserves to be further improved.Melamine-formaldehyde resin microsphere has been applied for adsorption of heavy metal ions,however,its application in emerging contaminants has not been reported.When incorporating macropores into mesoporous microspheres,hierarchically structured porous microspheres were constructed,which benefit from each hierarchy and become attractive in numerous realms such as separation,catalysis,energy,optics and even biomedicine.On account of the above considerations,in the present thesis,hierarchically meso-/macroporous flow-through silica microspheres（FTSM）and mesoporous melamine-formaldehyde resin microspheres（MMFRS）were synthesized through suspension polymerization,respectively.The good immobilization capacity for macromolecules,fast mass transfer character,and favorable separation property of FTSM and the excellent adsorption performance of perfluorooctanoic acid（PFOA）were explored,successively.The specific contents of research are as follows:1.FTSM was synthesized through suspension polymerization,and directly applied as the stationary phase of HILIC.Seven water-soluble vitamins（WSVs）achieved complete separation within 2.2 min.The quantitative determination method of WSVs based on fast HILIC was developed and validated systematically and then applied to the fast determination of the WSVs in vitamin beverages.This chapter exhibited the fast mass transfer character of FTSM in chromatographic separations and might provide a fast and applicable method for the the determination of WSVs in food and pharmaceuticals matrix.2.To solve the defect of the peak tailing of alkaline analytes occurring on silica-based stationary phases,a series of C18 and diol groups modified stationary phases based on FTSM were prepared by polar-copolymerization（PC）method.The wetness of silica and the ratio of diol groups have great influence on the chromatographic performance of stationary phases,which were investigated in detail.Some representative alkaline analytes achieved good separation on the stationary phase prepared through PC method under the optimal conditions.In comparison with conventional bonding method,PC method could increase the bonding amount of silicon alkyl groups,and have better shielding effects for the silanols thus leading to a better improvement for the peak tailing of alkaline analytes.In addition,PC method could block the micropores of the silica to some extent,improve the hydrophilicity and alkali-stability of the silica-based reversed-phase chromatographic stationary phase and simultaneously maintain favorable hydrophobic separation ability.The study improved the application performance of FTSM in the reversed-phase separation of alkaline and polar analytes.3.Catalase was immobilized onto FTSM through glutaraldehyde crosslinking and physical adsorption,respectively.The immobilization amount,catalytical activity,stability and reusability of the immobilized catalase（IMCAT）were investigated detailly.When compared with traditional mesoporous silica,FTSM exhibited higher immobilization amount and comparable catalytical activity with free enzyme in both methods,owing to the flow-through macropores.The IMCATs prepared by the two methods possessed similar immobilization amount,catalytical activity and stability;additionally,in physical adsorption method,the introduction of C8 groups was beneficial for the immobilization compared with bare FTSM;the combination of the enzyme and the carrier is free of chemical reactions,thus a more facile preparation process;however,the reusability of IMCATs prepared through adsorption was inferior to which prepared through glutaraldehyde crosslinking method accordingly.The excellent performance of the IMCATs prepared by the two methods revealed the application superiorities of FTSM in enzyme immobilization realms.4.Owing to the instability of silica under alkaline conditions,waxberry-like ethyl-bridged hybrid flow-through silica microspheres（WEHS）which possess favorable alkali-stability were successfully synthesized.The characterization revealed that,the more the ethyl-bridge groups were incorporated in,the smaller the macropores and mesopores were,the stronger the alkali-stability was resulted.In comparison with pure flow-through silica,when applied to lipase immobilization,the alkali-stable WEHS could exert the highest catalytic activity of lipase and exhibited better reusability under alkaline operational environment;as the stationary phase matrix of HPLC,WEHS also exhibited better tolerance with alkaline mobile phase and achieved ultra-fast and efficient separation.The study improved the alkali-stability of FTSM and laid a foundation for the exploration of hybrid FTSM materials.5.MMFRS with numerous mesopores and high anion-exchange capacity was fabricated through suspension polymerization and applied for the adsorption of PFOA in water.The preparation was cost-effective and the adsorption process was facile.MMFRS could be applied for the removal of PFOA in a wide pH and temperature range and almost impervious to the co-existed substances in aquatic environment.MMFRS exhibited a superiority over powdered activated carbons in terms of the adsorption amount,and the sorption could reach equilibrium within 24 h.In addition,the MMFRS could be easily and economically regenerated by dilute NH₃·H₂O,and possessed favorable reusability（>85%）after manifold cycles.The sorption kinetics obeyed to pseudo-second-order model and the sorption isotherms fitted both Freundlich and Langmuir models.This chapter proved the potency and superiorities of MMFRS when applied as adsorbents to remove perfluorooctanoic acid.