Radiation Synthesis Of Ionic Liquids Bonded Silica-based Materials And Their Adsorption Performance For Technetium/Rhenium

Technetium-99(⁹⁹Tc)is one of the most important nuclides in radioactive waste disposal because of its long half-life,high fission yield,and high environmental mobility.The development of efficient Tc separation methods is a prerequisite for the safe disposal of Tc.Due to the radioactivity of Tc,rhenium(Re),which has similar properties to Tc,has been widely studied as the analogue of Tc.Besides,Re is a rare metal with excellent properties,and the separation and recovery of Re has important research value and application prospect.Adsorption is considered to be one of the most efficient methods for separating technetium and rhenium.However,there are still some problems of the adsorbents for technetium and rhenium,such as low adsorption capacity,poor selectivity,poor radiation resistance,complex synthesis process and high cost.In order to solve the above problems,a series of novel adsorbents with excellent adsorption performance and good radiation resistance were successfully prepared via radiation grafting of ionic liquids onto silanized silica.The structure-activity relationship,adsorption mechanism and application prospect of prepared adsorbents towards Re(?)were studied in detail.The main research contents and results of this paper are as follows:(1)Three kinds of ionic liquids immobilized silica-based adsorbents were synthesized using the radiation-induced grafting of 4-vinylbenzyl chloride onto silanized silica and subsequent functionalization with different alkyl imidazoles.These adsorbents exhibited excellent radiation resistance,and their adsorption performance barely changed after 800k Gy radiation of electron beam or?-ray.The results of XPS and FT-IR analysis confirmed that the adsorption proceeded via an ion-exchange mechanism.The column experiment results showed that they could selectively separate Tc O₄^-/Re O₄^-from a variety of fission products,and had an excellent recycling performance.(2)Five kinds of adsorbents were prepared via grafting imidazole ionic liquids with different alkyl side chains onto silanized silica using electron beam radiation technique.These adsorbents exhibited an adsorption capacity of all about 190 mg/g for Re(?).The batch adsorption experimental results showed that the length of alkyl chain had no significant effect on the adsorption capacity and adsorption rate.The adsorbents with longer alkyl chains showed better selectivity against Re(?)under the conditions of strong acidic and large excess of competitive ions.Besides,its adsorption performance remained almost unchanged after ten cycles in column adsorption experiments.(3)Four kinds of adsorbents modified with ionic liquids containing different anions were synthesized using radiation grafting and anion replacement.These four adsorption materials have high ionic liquid molar content(1.503?2.375 mmol/g),and the maximum adsorption capacity of these adsorbents was 147.93?289.02 mg/g.The batch adsorption experimental results showed that the adsorption ability of prepared adsorbents was related to the anion structure of ionic liquid,and the anions with smaller radius and stronger hydrophilicity were more favorable for the adsorption process.The results of the column experiments showed that they could selectively capture Re(?)from the coexistence of multiple cations and anions,which were expected to be used in the efficient separation of Tc(?)from Hanford wastewater and other acidic radioactive wastewater.(4)1-vinyl-3 benzylimidazole chloride ionic liquid was synthesized and grafted onto three kinds of mesoporous silica with different pore volumes and specific surface areas using electron beam induced radiation grafting.The adsorbents with similar grafting yield were obtained by controlling the radiation grafting conditions.The adsorption experiment results showed that the adsorbents with larger specific surface area and pore volume have better adsorption performance.The maximum adsorption capacity of these three adsorbents was 138.31?204.92 mg/g,and they still remain high adsorption capacity after irradiated by gamma rays with a dose of 1200 k Gy in dry or wet conditions.(5)The separation of Re(?)from acid leaching solution of simulated uranium ore using silica-based adsorbents modified by imidazolium ionic liquids with different structures were studied via column experiments.The results showed that the adsorbents with long alkyl chain could efficiently adsorb and desorb Re(?)but hardly adsorb U(?).Besides,the adsorbents with short alkyl chain could adsorb U(?)and Re(?)at the same time,and the adsorbed U(?)and Re(?)could be separated via a step-by-step elution method.