Construction Of Polyoxometalates Functionalized Copolymer Self-assemblies And Study On Cs~+ Adsorption

Cesium is an important rare alkali metal which plays an increasingly important role in many high-tech fields,and Qinghai Salt Lake is rich in cesium resources.Therefore,it is of great significance to develop efficient separation and extraction technology for cesium in salt lake brine system.Ammonium phosphomolybdate?AMP?is a typical polyoxometalates,which has good specific adsorption performance for Cs⁺.However,because it is very soluble in water which make it difficult to separate and extract Cs⁺ from aqueous solution by AMP alone as an adsorbent.At present,the commonly used method is AMP to form a composite adsorption material with other materials.Therefore,in this paper,AMP was used as the Cs⁺ inorganic exchange phase,and temperature-sensitive block copolymers of P?St-co-AA?-b-PNIPAM and P?NIPAM-co-AA?-b-PSt were used as supporting AMP-loaded carriers.Additionaly,the four self-assemblies containg micelles P?St-co-AA-AMP?-b-PNIPAM,micelles P?NIPAM-co-AA-AMP?-b-PSt,nanotubes P?St-co-AA-AMP?-b-PNIPAM and nanotube P?NIPAM-co-AA-AMP?-b-PSt have been built basing on the principle of self-assembly.Which were used as Cs⁺ adsorbents,respectively,to study the adsorption performance for Cs⁺ in aqueous solution.First,the effects of factors such as the initial concentration of Cs⁺,the pH value of the solution,the number of cyclesand and the amount of adsorbent added on the adsorption effect were studied,then the optimal adsorption conditions and the stability and reproducibility of the four self-assemblies were discussed.Secondly,the mechanism of Cs⁺ adsorption by four self-assembled bodies was revealed using adsorption kinetics,adsorption isotherms and selective adsorption mechanism.The experimental results show that the adsorption process of Cs⁺ by the four self-assemblies conforms to the Quasi-second-order kinetic model and the Langmuir isotherm adsorption model.The adsorption equilibrium is reached within 3 h and the maximum adsorption amounts are 71.78751 mg/g,164.200361 mg/g,and 67.47638,mg/g and 49.8008 mg/g,respectively,and the mechanism of selective adsorption is the exchange between Cs⁺ and NH₄⁺ in the gap of AMP structure.Finally,considering the ease of construction of self-assemblies and its adsorption performance parameters,micelles P?NIPAM-co-AA-AMP?-b-PSt among them were considered to be the most suitable adsorption material for the separation and extraction of Cs⁺ in salt lake brine system.