Preparation Of Phosphate Functionalized Mesoporous Materials And Studies On Behavior And Mechanism Of Lanthanum Ions Selective Adsorption And Separation

Rare earth elements are widely used in the fields of catalysis,optics and magnetism due to their unique physicochemical properties.However,the excessive consumption and exploitation of REEs lead to a rapid decline in the amount of rare earths and a serious waste of resources.On the other hand,the increase in industrial applications may be accompanied by the accumulation of rare earth product waste in the ecological environment,causing public and ecological health risks.Therefore,the separation of rare earth elements has extremely high economic value and ecological value.The adsorption method based on mesoporous materials is widely used in the rare earth separation field due to its advantages of simple equipment requirements,low cost,high recovery efficiency and green environmental protection.In this paper,a series of phosphate functionalized mesoporous silica materials were synthesized by using soft template method,hard template method,copolycondensation method,post-grafting method and evaporation induction self-assembly method,which were used for selective adsorption and separation of rare earth ions?La????.In this system,EO₂₀PO₇₀EO₂₀?P123?and nanocrystalline celluloses?NCCs?were used as structure-oriented templates,respectively.The physicochemical properties of these adsorbent materials such as morphology,void structure,composition,surface properties and stability were analyzed by system characterization.The adsorption behavior and mechanism of the adsorbent were investigated by testing the adsorption capacity,adsorption kinetics,selectivity and cycle of La???adsorbed by adsorbent.The main work of this paper is as follows:?1?We successfully preparaed phosphate functionalized mesoporous silica material by copolycondensation method where P123 was used as a soft template and diethylphosphoryltriethoxysilane?PETES?was used as a functional monomer,for efficient selective adsorption separation of La???.By adjusting the ratio of silica source and functional monomer,the difference in structure of adsorbed materials and the change in adsorption performance were investigated.Among them,the SBA-15adsorbent?S2?exhibited a highly ordered hexagonal unit cell structure.At 25°C and pH was 7.0,the saturated adsorption capacity of S2 to La???was 114.81 mg g^-1,which is much larger than other adsorbent materials reported so far.In addition,S2has superior adsorption kinetics:it quickly reaches the adsorption equilibrium within60 min.The distribution coefficients?K_d?of S2 to La???was 725 mL g^-1,and the K_d value of other ions such as Nd???is about 200 mL g^-1,which indicated that the phosphate functionalized adsorbent has a strong selectivity in the adsorption separation process of La???.The cycle performance tests showed that the adsorbent had excellent regenerability for La???.A series of performance tests phosphate functionalized SBA-15 adsorbent?S2?has potential applications in the actual adsorption separation of La???.?2?Two types of chiral nematic mesoporous silica films were prepared via the direct copolymerization?MSFs-1?and post-grafting?MSFs-2?,respectively,for the selective adsorption of La?III?.Nanocrystalline celluloses?NCCs?were applied as a structural oriented bio-template and phosphate groups with specific recognition ability for La?III?were modified on the surface of both films.The films retained the well-ordered chiral nematic structure with large surface area and uniform pore size after the removal of NCCs without any disruption of organosilica frameworks.Both MSFs-1 and MSFs-2 showed strong adsorption affinity for La?III?with the maximum adsorption capacity of 77.74 and 69.24 mg g^-1 at pH was 7.0,respectively.The distribution coefficients for La?III?was 832 mL g^-1 for MSFs-1 and 805 mL g^-1 for MSFs-2,which were much higher than other interfering ions,indicating two type of films possessed a good selectivity for La?III?.Furthermore,the MSFs exhibited the excellent regeneration ability,showing potential application possibility for the selective adsorption of La?III?.?3?In order to improve the application potential of silica films materials,GO-doped phosphate functionalized chiral nematic mesoporous silica films?GO/MSFs?were prepared by evaporation-induced self-assembly method where NCCs was used as a hard template and PETES was used as a functional monomer.GO acted as a pore-enlarging agent in the synthesis of mesoporous silica films.The GO/MSFs pore size was increased by about 4.0 times compared with the unadded silica films,which effectively increased the mass transfer rate and achieves adsorption equilibrium within 2.5 h.In addition,GO-doped modification can improve the mechanical properties of the silica films,facilitate the adsorption and recovery process operations,and avoid large mass loss.When the doped ratio?mass ratio?of TEOS/GO was 5/1,GO/MSFs exhibited the best adsorption capacity,and the saturated adsorption capacity was 83.79 mg g^-1.The study found that the isotherm adsorption process was more suitable for the Langmuir equation.In addition,the phosphate functionalized mesoporous silica films exhibited superior selectivity and reusability.The above results indicated that GO/MSFs can be an economical adsorbent for the efficient selective adsorption of La???.