Preparation Of Zirconium Phosphate Based Adsorbent And Its Adsorption And Enrichment Of Rare Earth La³⁺

The in-situ leaching process is commonly used in ionic rare earth mining,and a large amount of low-concentration rare earth tailwater is often produced after mining.If these tail waters are not treated effectively,rare earth resources will be wasted.Compared with other methods,the adsorption method is more suitable for the recovery of low-concentration rare earth elements in tail water,and the development of high-performance adsorbents is the key to the adsorption method.Zirconium phosphate（Zr P）material has excellent ion exchange performance,thermal stability and good acid resistance,it is expected to be used in the enrichment and recovery of rare earth elements.In this paper,zirconium oxychloride（Zr OCl₂·8H₂O）was used as zirconium source to prepare amorphous Zr P andα-Zr P by precipitation method and hydrothermal method,respectively.Further,α-Zr P was exfoliated with tetrabutylammonium hydroxide（TBAOH）,then respectively Graft modification using3-aminopropyltriethoxysilane（APTES）and 3-mercaptopropyltriethoxysilane（MPTMS）were used for Amino-modified zirconium phosphate and sulfonic acid group-modified zirconium phosphate.Used by scanning electron microscopy（SEM）,X-ray diffraction analysis（XRD）,infrared spectroscopy（FTIR）and X-ray photoelectron spectroscopy（XPS）,the materials were characterized,and the adsorption properties,thermodynamic and kinetic properties and desorption regeneration laws of the four materials,amorphous andα-Zr P and amino and sulfonic acid group modified Zr P,for rare earth La³⁺were explored.It’s support for the enrichment and recovery of low-concentration rare earth resources.The effects of contact time,initial concentration,temperature,p H,impurity ions Al³⁺and NH₄⁺on the adsorption of La³⁺were determined by static adsorption experiments.The results show that the adsorption equilibrium times of amorphous Zr P,α-Zr P,amino-modified Zr P and sulfonic acid-modified Zr P for La³⁺are 10,5,90 and5 min,respectively;The maximum La³⁺adsorption capacity at room temperature was183.7,37.1,142.3 and 130.3 mg/g,respectively;The p H range of the best adsorption is 4-8,6-7,4-8 and 2-8 respectively,and the sulfonic acid group-modified Zr P is suitable for more acidic solutions;The adsorption capacity of La³⁺increased with the increase of temperature.The coexistence of impurity ions Al³⁺can significantly reduce the adsorption capacity of amorphous Zr P,α-Zr P and amino-modifiedα-Zr P on La³⁺,while the sulfonic acid group-modified Zr P has stronger resistance to the interference of impurity Al³⁺.In the case of C_La:C_Al=1:1,the adsorption capacity of La³⁺is still more than 40 mg/g.Compared with Al³⁺,NH₄⁺has little effect on the ability of four kinds of zirconium phosphate materials to adsorb rare earth La³⁺.The FTIR and XPS analysis of the materials after adsorbing La³⁺confirmed that all the four materials were involved in the adsorption of hydroxyl groups.The difference is that the functional groups added by amino and sulfonic acid modified Zr P simultaneously participate in the adsorption.The adsorption kinetics of La³⁺on four adsorbents was studied by pseudo-first-order and pseudo-second-order kinetic models.The results show that the adsorption of La³⁺by amorphous Zr P conforms to the pseudo-second-order kinetic model,which is controlled by the chemical adsorption mechanism,and the adsorption of La³⁺by the other three materials conforms to the pseudo-first-order kinetic model.Two adsorption isotherms,Langmuir and Freundlich,were used to characterize the adsorption process of La³⁺on four materials.The results show that adsorption of La³⁺by the four materials is consistent with the Langmuir adsorption isotherm model,and all are the monolayer adsorption of La³⁺on the surface of material.From the adsorption thermodynamic parameters,it can be seen that the adsorption of La³⁺by the four materials is a spontaneous reaction of endothermic entropy increase.The desorption regeneration study using HCl as desorbent showed that when the concentration was 0.3 mol/L,amorphous Zr P maintained more than 60%adsorption capacity after 5 cycles.At the concentration of 0.5 mol/L,amino-modified Zr P completely lost its adsorption capacity,whileα-Zr P and sulfonic acid-modified Zr P maintained 76%and 89.5%of the adsorption capacity,respectively.Based on the above research results,zirconium phosphate materials have the potential to be developed into rare earth element adsorbents.Among them,the sulfonic acid-modified Zr P has more advantages than other researched zirconium phosphate-based materials in terms of adsorption capacity,adsorption selectivity,acid resistance and desorption regeneration.