Controllable Fabrication Of Sulfonated Particles And Their Ion Exchange Property Investigation

Ion exchange resins have been widely used in the fields of exchange,catalysis,adsorption and separation.Polystyrene microspheres have great application prospects in the field of ion exchange because of their controllable of cross-linking density,easy functionalization of benzene rings,excellent mechanical properties,and low production cost.The strongly acidic cation exchange resin which is formed by sulphonation of polystyrene microspheres is widely used in various industries due to its simple preparation process,good exchange performance and stable physical and chemical properties.In the industry route,cross-linked polystyrene microspheres are prepared by suspension polymerization.The microspheres are then sulfonated to produce sulfonated polystyrene ion exchange resins.However,most of the prepared resins are usually spherical with smooth surfaces.The modified ion-exchange sitesat the surface only lead to a low ion exchange capacity.Therefore,it is still a very challenging task to prepare microspheres with special morphology,high surface area and large amount of active site for increasing the ion exchange capacity.This paper is mainly divided into two parts.In the first part,the shaped polymer microspheres derived from therandom copolymerization of styrene and 2-acrylamide-2-methylpropane sulfonic acid(PSt-co-AMPS)were synthesized by emulsifier-free emulsion polymerization,and the polymer microspheres weremodified by sulfonation agent.At last,a novel sulfonated shaped polymer microsphere was prepared.In the second part,a sulfonated polystyrene,mesoporous silica microsphere with yolk-shell structure was synthesized.At last,westudy on the ion exchange performance of microspheres modified by sulfonation with chlorosulfonic acid.The contents ofthe work are as follows:(1)Cross-linked PSt-co-AMPS microspheres were synthesized by emulsifier-free emulsion polymerization and sulfonated by chlorosulfonic acid.The effects of monomer ratio,reaction conditions and other factors on the morphology of the microspheres were discussed.The SEM and TEM were used to study the mechanism for the formation of the final morphology.The composition of the microspheres was analyzed using Fourier Transform Infrared(FT-IR)and elemental analyzers.Due to the hydrophilic group sulfonic acid groups in the monomer during the polymerization process,the microspheres had water absorption properties.Pores could be formed on the microspheres after freeze-dring and the microspheres are sulfonated.The results showed that under the conditions of reaction temperature 60?,with 10 mL of chlorosulfonic acid and reaction time of 6 h,the maximum ion exchange capacity of sulfonated cross-linked PSt-co-AMPS polymer microspheres could reach 4.96 mmol/g.The exchange capacity was better than some commercially available resins.(2)Polystyrene microspheres were prepared by emulsion polymerization.Ethyl orthosilicate(TEOS)was used for polycondensation on the surface of polystyrene microspheres to form a silica layer.The silica shell was etched with ammonia water.A phenyl-modified silica layer was formed using two silane coupling agents:1.2-bistrimethoxysilylethane(BTM E)and trimethoxyphenylsilane(PTMS).The surfactant hexadecyl trimethyl ammonium bromide was removed by solvent extraction process to creat mesoporous structure in the silica shell.Finally,a yolk-shell phenyl modified polystyrene@mesoporous silica microsphere was formed.Microspheres were sulfonated with chlorosulfonic acid.The effects of PTMS usage,reaction time and other factors on the micro-spherical morphology were discussed.The micro-spherical morphology was characterized by SEM and TEM.The composition of the microspheres was analyzed using an FT-IR spectrometer and an elemental analyzer.The sulphonation of the microspheres by using chlorosulfonic acid as a sulphonating agent aimed to modify a large amount of sulfonic acid groups in the inner core and outershell of the microspheres to increase the ion exchange sites.The results show that PSt@mesoporous silica microspheres without phenyl modification on the shell is a typical yolk-shell structure.After sulfonation,the measured ion exchange capacity is 2.4 mmol/g.The PSt@mesoporous silica microspheres which were modified by phenyl group were sulfonated and the ion exchange capacity increased to a maximum of 3.79 mmol/g.