Preparation Of Novel Phosphoric Acid Functional Materials And Study On Its Adsorption And Separation Behavior Of Cobalt,Neodymium,and Dysprosium

As a strategic resource,rare earth（REE）has attracted worldwide attention and are widely used in electronic information,transportation,industrial production,and defense and military applications due to their excellent optical and electromagnetic properties.With the rapid development of society and technology,the demand for REE is increasing.Therefore,the recovery of REE from secondary resources not only alleviates the urgent need for rare earths to a certain extent,but also contributes to environment protection.As one of the largest applications for rare earth,NdFeB permanent magnets are rich in rare earth elements such as neodymium（Nd）and dysprosium（Dy）as well as the rare metal cobalt（Co）,which have a high recovery value.For effective recovery of REE and Co from NdFeB simulants,in this work,two novel phosphoric acid functional adsorbent materials were prepared and evaluated for performance and mechanism analysis.The main results are as follows:（1）Using the sol-gel method,phosphoric acid functionalized hydrogel（DPPA/CaALG）was prepared by cross-linking reaction in CaCl₂ solution with n-dodecyl phosphate（DPPA）as functional group donor and sodium alginate as carrier,application to the adsorption and separation of Co-Nd-Dy from NdFeB simulants.SEM-EDS and BET characterization showed that DPPA was successfully loaded onto sodium alginate,which increases the specific surface area and pore space of sodium alginate.The acidity search revealed that DPPA/CaALG exhibited excellent adsorption selectivity for REE and almost no adsorption for Co,with the adsorption reaction being an H⁺exchange process.The adsorption of Nd and Dy by DPPA/CaALG reached adsorption equilibrium at 6 h.The maximum saturation capacity was 162.5 mg/g and 183.5 mg/g,respectively,and the adsorption behavior was in accordance with the pseudo-second-order adsorption kinetic model and Langmuir adsorption isotherm model,the whole adsorption process was monolayer chemisorption,and the adsorption capacity was enhanced with increasing the temperature.FT-IR and XPS analyses show that the adsorption of Nd and Dy by DPPA/CaALG is dominated by the exchange of H⁺in P-OH.The phosphate group becomes the chemically reactive center during adsorption by generalized functional density theory calculations（DFT）,and the energy gap and bond length of Nd-DPPA is greater than that of Dy-DPPA,implying a greater affinity of DPPA/CaALG for Dy.（2）DPPA/CaALG showed strong adsorption of Nd and Dy,but slow adsorption rate and low desorption efficiency as well as inability to perform continuous separation of Co-Nd-Dy through the column.Therefore,the mesoporous silica molecular sieve（SBA-15）was synthesized by hydrothermal method using poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol）（P123）as the template agent and tetraethyl orthosilicate（TEOS）as the silica source.The characterization by TEM,XRD,SEM-EDS,and BET showed that the PPA@APTES/SBA-15 composite was successfully prepared and the original porous morphology and structure were maintained after functionalization.The performance study showed that PPA@APTES/SBA-15 exhibited good adsorption performance for Nd and Dy and hardly adsorbed Co.which adsorption mechanism was H⁺exchange in P-OH and the adsorption equilibrium was reached at 10 s.The whole adsorption process was consistent with the pseudo-second-order adsorption kinetic model and Langmuir adsorption isotherm model,which indicates that the adsorption behavior was monolayer chemisorption.Desorption with 6M HCl gives nearly 100%desorption of Nd and Dy with good reusability.FT-IR,XPS and DFT analysis showed that Nd and Dy could be successfully adsorbed by PPA@APTES/SBA-15,and the adsorption process was dominated by H⁺exchange in P-OH.The column experimental study shows that PPA@APTES/SBA-15 can achieve the separation of Nd and the enrichment of Dy,which is expected to be an effective material to solve the difficulty of mutual separation of Nd and Dy.