Study On The Preparation Of Lanthanum-based Magnetic Nanomaterials And Its Mechanism Of Phosphate Adsorption And Influencing Factors

Water eutrophication is mainly caused by excessive phosphorus in water,so effectively removing phosphorus from water is an urgent problem to be solved.In this paper,the adsorbent with the best dephosphorization effect was determined through the comparison of various preparation methods,the comparison of various lanthanum morphologic magn-etic materials and the comparison of various preparation conditions.Because of its wide range of p H adaptation and small effect of co-existing ions,its application prospect in more complex water environment is improved and the difficulty of treating phosphorus-containing wastewater is reduced.In this paper,two preparation methods were investigated and the result showed that the adsorption effect and magnetic strength of La³⁺@Fe₃O₄,La（OH）₃@Fe₃O₄,La₂（CO₃）₃@Fe₃O₄ and La₂O₃@Fe₃O₄ prepared by"two-step method"is obviously more dominant than those of"one-step method".Then,under the same conditions,four lanthanum morphologic magnetic materials prepared by the"two-step method"were compared in terms of their phosphorus removal effect,and the four adsorbed materials were characterized.La³⁺@Fe₃O₄was screened out as the best lanthanum morphologic material,and the reason for the superior phosphorus removal effect of La³⁺@Fe₃O₄ was deduced.Then,this paper optimized the preparation conditions of La³⁺@Fe₃O₄ materials,investigated the effects of p H and co-existing ions,adsorption isotherms,adsorption kinetics and other adsorption properties under the optimal preparation conditions,and discussed the adsorption mechanism of La³⁺@Fe₃O₄ through the adsorption results and various characterization methods,These characterization methods include BET,SEM,TEM,XRF,VSM of five proportions,XRD before and after adsorption,infrared and Raman spectra before and after adsorption,Zeta potential analysis before and after adsorption,and XPS before and after adsorption.The experimental results show that the best preparation conditions of La³⁺@Fe₃O₄ are n（La:Fe）=4:1,the amount of sodium citrate is 6 g,and the stirring time is 0.5 h.The material is suitable for the environmental water body with a wide range of acidity and alkalinity,and the optimal adsorption effect can be achieved in the neutral water body,and the material is not disturbed by other co-existing ions.The material can be adsorbed and saturated within 3 h,and at the initial concentration of 25 mg/L,the maximum adsorption stable point is 78 mg/g,indicating that La³⁺@Fe₃O₄ has good adsorption stability and efficiency.The adsorption process of La³⁺@Fe₃O₄conforms to the Langmuir model and the quasi-secondary kinetic model,indicated that the material is a surface monolayer chemical adsorption.Various characterization of La³⁺@Fe₃O₄ material indicates that the material is dominated by coordination to adsorb phosphate ions,and the phosphate ions are combined with lanthanum ions to form lanthanum phosphate to complete the adsorption process.Moreover,the material is magnetic and has certain practical value.In the end,the reuse of materials and the ability to treat actual wastewater were investigated by screened desorption agents,determined desorption performance,completed adsorption desorption cycle and treated a variety of actual water bodies.In this study,the desorption agent was a mixture of 2.5 mol/L Na OH and 1.875 mol/L Na Cl.The optimal desorption time was 3 h.And the second order model can better describe the desorption process（R²=0.998）.The results of 20 desorption cycles showed that the adsorption capacity of La³⁺@Fe₃O₄ after 12 times of regeneration was more than 90%of that of the first adsorption capacity,which further enhances the application potential of La³⁺@Fe₃O₄ in actual water treatment.Then the adsorption experiments on four kinds of water bodies with different properties have proved that the material can adapt to the complex water quality environment and has a certain application prospect.