Amine-Directed Indium Sulfide Ion-Exchangers

With the rapid development of nuclear energy,a large amount of radioactive waste liquid has been produced.The effective disposal of nuclear waste liquid has become one of the important links for the development of nuclear industry.⁹⁰Sr(t_1/2= 28.8 a)is the fission product of nuclear fuel ²³⁵U and ²³⁹Pu which can emit β-rays（E_β = 0.546 MeV）.It has strong radioactivity and biological toxicity that usually exists in the form of divalent ions.By soil migration,crop absorption,into the food chain after enrichment in animals and plants,posing a potential threat to the ecological environment and human health.The chemical properties of Sr are similar to Ca,it is easy to replace Ca in human bones,leading to diseases such as leukemia,anemia and genetic variation.¹³³Ba(t_1/2= 10.7 a)in the same family as Sr is also one of the most toxic radionuclides in nuclear waste liquid.Ba²⁺and Sr²⁺have similar chemical properties with γ-rays（E_γ = 0.356MeV）which also increases the risk of human disease.In addition,⁶⁰Co(t_1/2= 5.3 a)and ⁶³Ni((t_1/2= 100.1 a)produced by neutron activation in nuclear reactor materials release γ-rays or β-rays,which are highly toxic and radioactive.Meanwhile,Co and Ni is also an important component of industrial wastewater,if not duly and effective treatment will seriously contaminate the environment and harm human health.Therefore,Therefore,it is of great significance to seek reasonable and effective methods to remove the radioisotopes of ⁹⁰Sr,¹³³Ba,⁶⁰Co and ⁶³Ni.In recent years,the rapid development of metal sulfide ion exchange materials has attracted extensive attention.On the one hand,soft basic S atoms in metal sulfide have a good affinity for Lewis soft acid ions Sr²⁺and Ba²⁺.On the other hand,metal sulfide ion-exchange materials show good framework flexibility and flexible coordination mode,and construct windows and channels of different shapes and sizes,which provide convenient transport routes for the exchange of ions.However,the adsorption capacity of metal sulfide ion-exchange materials reported at present is generally low.For example,the exchange capacity of Sr²⁺ions at the level of 20-100 mg g^-1,which is significantly lower than that of oxide materials such as titanosilicate(DTS 180 mg g^-1).Therefore,the design and improvement of the structure to enhance the exchange capacity of materials has become an important content in the research of sulfide ion-exchange materials.Based on the template synthesis technology of amines,this paper prepared new layered indium sulfide microporous materials InS-1 and InS-2 with high adsorption capacity by constructing "vacancy type" cluster and inducing large size window,and explored the adsorption behavior of Sr²⁺,Ba²⁺,Co²⁺and Ni²⁺ions of the materials.In addition,we further developed the application of amine template technology.In the synthesis of In and Ga based sulfide materials,and prepared a series of crystal materials based on cluster assembly.The specific content is as follows:1.The introduction of "vacancy type" clusters as structural elements to construct layered materials with high negative charge density [CH3CH2NH3]6In6S12（InS-1）greatly improves the theoretical exchange capacity of the materials.InS-1 can quickly adsorb low concentration（⁶ ppm）Sr2+ ions in aqueous solution at 24 hours,the removal rate can reach 98.5 % the saturated adsorption capacity reach 105.35 mg g-1.In addition,InS-1 is resistant to β and γ-ray irradiation exhibits good adsorption activity over a wide pH range（3-12）.The exchanged Sr2+ can be easily eluted with 0.5 M KCl solution.2.A novel layer material [CH3CH2NH3]6In8S15（InS-2）with large size perforated structure was synthesized by organic template structure agents.The anion lamellar part of InS-2 is assembled by [In8S17]10-cluster and the connection of four adjacent clusters forms a 24-ring window with the size of 17.25 × 11.20A2.The large size of the window facilitates the shuttling and storage of Sr2+ with a large hydration radius,which further increases the material exchange capacity to 143.29 mg g-1,the highest level of the same type of material reported so far.3.The adsorption capacity of InS-2 material for Ba2+,Ni2+ and Co2+ ions was studied,and the maximum adsorption capacity of 211.73,103.57 and 105.57 mg g-1,respectively,which was at a higher level among the reported sulfide ion exchangers.Kinetic result shows that InS-2 can adsorb Ba2+,Ni2+ and Co2+ ions quickly.Furthermore,by building an ion exchange column,we tested the treatment effect of the material for Ba2+,Ni2+ and Co2+ ions in the flowing solution.The result shows that this material can completely remove ions from the mixture of Sr2+,Ba2+,Ni2+ and Co2+ with a bed volume of 2600 times.4.Using mixed solvothermal technology,ammonia/amine template was successfully introduced into In/ Ga-based sulfides with mixed solution of amine-ethanol or deep eutectic solvent（DES）as reaction medium,and four novel materials based on supertetrahedral assembly were synthesized: [NH（CH₃）₃]₄In₄S₁₀H₄（1）,（NH₃）₄Ga₄S₆（2）,[NH₃CH₂CH₃]₅（NH₂CH₂CH₃）₂Ga₁₁S₁₉（3）,[NH₃CH₂CH₂OH]₆Ga₁₀S₁₈·2NH₂CH₂CH₂OH（4）The synthesis conditions and structural characteristics of the above four compounds were investigated in detail,and the structural guiding effect of ammonia/amine template was emphatically discussed.