Magnetic Titanium Dioxide Fe₃O₄@TiO₂ Study On The Surface Modification And Adsorption Of Rare Earth La³⁺

With industrial development and technological innovation,the resource demand for ionic rare earth ores is increasing.Ionic rare-earth ores generate a large amount of low-concentration rare-earth wastewater after the in situ leaching process,which not only leads to the loss of natural resources but also causes environmental pollution.Compared with other methods,adsorption is of great interest for enriching rare earth elements in wastewater because it is fast,convenient,green and low cost.TiO₂has good stability,low cost and biocompatibility,but due to its fine particles,it is difficult to achieve solid-liquid separation,which easily leads to secondary pollution.To solve this problem,the combination of magnetic nanoparticles Fe₃O₄and TiO₂can effectively improve its performance.In this paper,Fe₃O₄@TiO₂with core-shell structure was synthesized by a combination of hydrothermal and sol-gel methods,and the surface modification was carried out by Na OH and phosphate treatment to prepare Fe₃O₄@f TiO₂with fibrous structure and Fe₃O₄@Ti P contained phosphate groups,respectively.The adsorption behavior,adsorption mechanism and desorption regenerability.The main contents and conclusions are as follows:（1）The results of static adsorption experiments showed that the adsorption equilibrium times for La³⁺were 15 min and 240 min for Fe₃O₄@f TiO₂and Fe₃O₄@Ti P,respectively,and the maximum adsorption capacities for La³⁺at room temperature were 142.88 mg·g^-1and164.4 mg·g^-1,respectively.the best adsorption p H ranges were both in the range of 4-5,with good acid resistance.The fitting results of the adsorption models showed that the adsorption behavior of Fe₃O₄@f TiO₂on La³⁺was more in accordance with the pseudo primary kinetic model,while the adsorption process of Fe₃O₄@Ti P on La³⁺was in accordance with the pseudo secondary kinetic model.The adsorption behaviors of both materials are consistent with the Langmuir isothermal adsorption model and the thermodynamic parameters indicate that the adsorption of La³⁺by both materials is a thermodynamic process with spontaneous heat absorption.In addition,impurity ions other than Al³⁺have less influence on the adsorption of La³⁺by Fe₃O₄@f TiO₂,while Fe₃O₄@Ti P is not only seriously affected by Al³⁺,but the presence of Mg²⁺and Ca²⁺also inhibits the adsorption of La³⁺by Fe₃O₄@Ti P.（2）The analysis of Fe₃O₄@f TiO₂and Fe₃O₄@Ti P using TEM,BET,VSM,and XPS characterization techniques showed that both materials have core-shell structure and TiO₂wrapped uniformly.The specific surface areas of the two modified materials are as high as86.81 m²·g^-1and 93.21 m²·g^-1,respectively,and they have good superparamagnetic properties(saturation magnetization strengths of 30.82 emu·g^-1and 12.75 emu·g^-1,respectively).XPS,FT-IR and XRD of Fe₃O₄@f TiO₂and Fe₃O₄@Ti P before and after adsorption of La³⁺analysis showed that the external shell layers of both adsorbents were amorphous structures,and the adsorbents had good acid resistance and stability under acidic conditions.（3）The influence law of the desorption regeneration of Fe₃O₄@f TiO₂and Fe₃O₄@Ti P was studied in four aspects of desorbent type,concentration,dosage and desorption time to screen the best desorption process parameters.The experimental results showed that 10 mg Fe₃O₄@f TiO₂was best desorbed by 20 m L of 0.05 mol·L^-1HCl solution for 60 min with the desorption amount of 133 mg·g^-1.10 mg Fe₃O₄@Ti P was best desorbed by 20 m L of 0.1mol·L^-1HCl solution for 60 min with the desorption amount of In addition,both adsorbents were able to maintain more than 65%of the initial adsorption capacity after 5 cycles.