Ball-milling synthesis of organic porous materials with tetraphenylmethane for iodine vapor adsorption
Objective Radioactive isotopes of iodine,such as iodine-129 and iodine-131,are prevalent contaminants during nuclear energy utilization.Managing radioactive iodine is a critical concern for researchers and the use of porous materials for iodine vapor adsorption presents a promising solution.However,traditional porous iodine adsorbents,including activated carbon and porous zeolite,exhibit drawbacks such as high density,limited structural versatility,low specific surface area,large pore size,low adsorption capacity,and inadequate cycling performance,significantly impeding their industrial applicability.Given these chal-lenges,it is necessary to develop novel porous materials for efficient iodine vapor adsorption.Porous Organic Polymers(POPs)emerge as a potential solution,characterized by high physical and chemical stability,low density,high porosity,large specific surface area,outstanding adsorption performance,and recyclability,offering a promising prospects in radioactive iodine treat-ment.Ball mills,as common crushing equipment,find widespread application in industries such as mineral processing,build-ing materials,and chemical industry.Furthermore,researchers use ball mills for chemical synthesis due to their advantages such as brief reaction times,high efficiency,simplicity,and potential for low-cost,straightforward,large-scale industrial pro-duction.In this study,tetraphenylmethane,featuring a three-dimensional structure served as the monomer,while a high-energy planetary ball mill functioned as a reactor,enabling swift and efficient construction of three POPs materials.These materi-als were evaluated for their adsorption performance and recycling ability in a simulated radioactive iodine vapor environment.Our research offers a viable solution for large-scale production of POPs materials and their practical application in iodine vapor adsorption.Methods In this study,we successfully synthesized three distinct porous organic polymers(POPs),namely T-FDA,T-DCM,and T-DCE,utilizing a rapid and efficient ball milling approach.This method resulted in materials characterized by high spe-cific surface area and abundant pore structure.The synthesis process involved employing tetraphenylmethane as a three-dimensional structure monomer,along with either anhydrous ferric chloride or anhydrous aluminum trichloride as catalysts,and three different crosslinking agents(dimethoxymethane,dichloromethane,and 1,2-dichloroethane)to generate the aforemen-tioned POPs materials.The synthesis procedure commenced by introducing the requisite reagents into a 250 mL zirconia grinding jar containing 50 zirconia spheres(Diameter:10 mm).After purging the jar with an argon atmosphere and sealing it,the plan-etary high-energy ball mill was set to a revolution speed and rotation speed of 400 r/min,with the milling process lasting for 2 hours at room temperature.Subsequently,the iodine vapor adsorption capacity of the porous materials was evaluated.Specifi-cally,0.2 g of POPs powders were accurately weighed and placed into a pre-weighed small sample bottle while 2 g of iodine was introduced into another sample bottle.These two bottles were then positioned within a glass container to create a sealed sys-tem,which was subsequently transferred into an oven set at 75 ℃ to expose the powder to a saturated iodine vapor environment.At predetermined time intervals(1,2,3,4,5,6,8,12,16,20,and 24 hours),the sealed container was removed from the oven and rapidly cooled,following which the mass of the sample bottle was accurately determined.Results and Discussion The resulting porous materials,T-FDA,T-DCM,and T-DCE,exhibited high specific surface area(398,516,and 753 m2/g respectively),abundant pore channels,and excellent structural stability.These materials were char-acterized by a significant presence of micropores(＜2 nm)and even ultra-micropores(＜0.7 nm),alongside a certain proportion of mesopores.The interconnected nature of these pores gave unique advantages to the materials,particularly in the realm of adsorption,notably in the adsorption and separation of gas substances such as radioactive iodine vapor.Based on experimental findings,the iodine adsorption capacity of T-FDA,T-DCM,and T-DCE could reach up to 461％,486％,and 444％respec-tively.These materials achieved adsorption saturation at the 5th,8th,and 6th hour respectively.Furthermore,to assess the materials'cycling performance,iodine vapor adsorption recycling experiments were conducted five times for each of T-FDA,T-DCM,and T-DCE.The results indicated that the iodine vapor adsorption efficiency of T-FDA only slightly decreased after five cycles of use,with the iodine vapor adsorption amount reducing from 461％initially to 454％after the fifth cycling,representing a decrease of only 1.5％.For T-DCM,its iodine vapor adsorption capacity decreased from 486％in the first time to 473％in the fifth time,corresponding to a reduction of 2.7％.Similarly,the iodine vapor adsorption of T-DCE decreased from 444％in the first time to 414％in the fifth time,with a reduction of 6.8％.Notably,the iodine adsorption performance of the three porous materials only slightly decreased after five cycles of use.Conclusion In this study,utilizing the ball-milling method,three porous materials(T-FDA,T-DCM,and T-DCE)were syn-thesized within a remarkably short period of 2 hours.Subsequently,structural analyses and iodine vapor adsorption performance of these materials were conducted.Our findings revealed that T-FDA,T-DCM,and T-DCE exhibited specific surface areas of 398,516,and 753 m2/g,respectively.These materials showcased abundant micropores,continuous multi-level pore distribu-tion,and a relatively stable structure.To assess their practical utility,we applied these porous materials to iodine vapor adsorp-tion in a closed system operating at 75 ℃,simulating the vapor evaporation environment of radioactive iodine with standard iodine elements.The experimental outcomes demonstrated impressive iodine adsorption mass fractions of 461％,486％,and 444％for T-FDA,T-DCM,and T-DCE,respectively.Remarkably,these materials exhibited reusability for up to 5 cycles with only a marginal decrease in performance(≤6.8％).Our results underscore the exceptional iodine vapor adsorption performance of the porous materials synthesized via fast ball milling,suggesting their potential significance in the context of radioactive iodine adsorption.Moreover,the ball milling synthetic method offers advantages including short reaction time,high efficiency,low energy consumption,and avoidance of extensive energy and organic solvent usage,thereby harboring considerable potential for large-scale industrial production.
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