Basic Research On Synthesis And Application Of Cesium Ion Sieve

Cesium（Cs-133）is an excellent rare alkali metal,which is widely used in electronic devices,medical treatment,new energy,aerospace,information industry and other fields.The reserves of liquid mineral cesium resources are huge,and it exists in ionic form in resources such as brine from salt lakes,extracted water from oil fields,and concentrated seawater after desalination.Extraction and recovery of Cs⁺from liquid minerals is a very meaningful work.Therefore,the extraction of Cs⁺from solution is of great importance for cesium resource recovery.In this paper,Cs₂Ti₆O₁₃（CTO）precursors were firstly synthesized by the solvothermal method and acid-modified to form H-type nanosheet cesium ion sieves（H-CTO）.The intrinsic connection and laws between the controllable preparation conditions of CTO,the structure of cesium ion sieve（H-CTO）and the exchange ion selectivity were investigated,and the adsorption kinetics,thermodynamics and ion exchange adsorption mechanism of cesium ion sieve（H-CTO）were thoroughly studied.In addition,Cs_0.68Ti_1.83O₄（CTO-1）precursor was prepared in one step by improved solid-phase method,and its acid reforming was used to generate H-type nanosheet cesium ion sieve（HTO-1）.It was compared with the ion sieve（HTO-2）synthesized by the conventional solid-phase method,and the conditions for the preparation of HTO-1 ion sieve were optimized.Secondly,the HTO-1 was further granulated/formed to form the HTO-1-PVC-x composite ion sieve by the anti-solvent method,and its ion-exchange properties were investigated to provide basic data support for industrial applications.The main studies are:（1）CTO precursor was synthesized by solvothermal method and heat treatment,and then acid modified to produce H-CTO nano-sheet ionic sieve.A series of intermittent adsorption experiments were conducted.The effects of p H,contact time,temperature,initial Cs⁺concentration,and interfering ions on Cs⁺adsorption were studied.The experiment shows that H-CTO has a larger adsorption capacity（329 mg/g）and better cycle performance than the currently reported titanium based adsorbent.The Cs⁺is easily eluted by 0.2M HCl solution;After five cycles,there was no significant decrease in the adsorption capacity.In addition,the adsorption behavior of Cs⁺on H-CTO can be described by Langmuir isotherm and pseudo-secondary kinetic models.The IR and Raman spectroscopic characterization indicated that the adsorption mechanism of Cs⁺on H-CTO included O-H bond breaking and O-Cs bond formation.Thermodynamic studies show that low temperature is conducive to the adsorption of Cs⁺and is spontaneous.（2）CTO-1 precursor was synthesized by improved solid phase method in one step,and its acid was modified to form HTO-1 ionic sieve for the adsorption or removal of Cs⁺.Compared with HTO-2 synthesized by traditional solid phase method,this method can effectively inhibit particle agglomeration.The saturated adsorption capacity of HTO-1 reached 299 mg/g in 2 hours,and the saturated adsorption capacity increased by 40 mg/g.Secondly,spherical HTO-1-PVC-x composites were synthesized by anti-solvent method for HTO-1.Taking HTO-1-PVC-10 as the research object,the ion exchange performance of HTO-1-PVC-10 was investigated.The maximum adsorption of HTO-1-PVC-10 was 263 mg/g at the initial concentrations of Cs⁺of 3000 mg/L and298.15 K.The adsorption behavior of HTO-PVC-10 on Cs⁺was in accordance with the Langmuir isotherm model and the pseudo-second-order model,which is a chemisorption process.In alkaline environment,its adsorption efficiency reaches 92.58%within 4 hours.The adsorption selection experiments shows that Cs⁺is easy to combine with the O^2-adsorption site of HTO-1-PVC-10,and the electrostatic effect is greater than other ions.The cycle performance test showed that the adsorption capacity did not decrease significantly after five cycles.These results show that cesium ion sieve has good selectivity,stability and large adsorption capacity in Cs⁺solution,and is a functional material with application prospect.