Preparation And Phosphorus Removal Performance Of Lanthanum-functionalized Silica Aerogel Microspheres

Phosphorus is one of the important reasons for the eutrophication of water.Among the existing phosphorus removal methods,adsorption method has been widely used and studied because of its advantages such as large adsorption capacity,low energy consumption,fast rate and low pollution.However,in practical application,most of the adsorption materials used are in the form of powder,which is difficult to aggregate and recover.Therefore,it is necessary to develop a functional composite material to remove phosphate in water more efficiently.However,in practical application,most of the adsorption materials used are in the form of powder,which is difficult to aggregate and recover.Therefore,it is necessary to develop a functional composite material to remove phosphate in water more efficiently.SiO₂ aerogel microsphere is a kind of nanoporous material with high specific surface area.Sodium alginate(SA)has been widely used in the study of phosphorus removal due to its non-toxic,biodegradable and easy modification.Because of its good chemical stability,polyvinyl alcohol(PVA)has been widely used in many fields such as environment.Lanthanum(La)is an environmentally friendly and relatively cheap rare earth element,which has a strong affinity for phosphate.Therefore,two kinds of lanthanum functionalized silica aerogel microspheres composites were prepared in this paper by using SA and PVA as cross-linking carriers,coating SiO₂ aerogel microspheres and cross-linking with La ions.Firstly,lanthanum functionalized silica aerogel microspheres/sodium alginate composite(LA-SiO₂/SA)was prepared.The effects of the ratio of SiO₂ aerogel microspheres to SA and PVA,the concentration of crosslinking agent and the crosslinking time on the adsorption performance were investigated.When the optimal ratio of SA and SiO₂ aerogel microspheres was 1:3,the optimal cross-linking agent concentration was 7%,and the optimal cross-linking time was 12 h,the maximum removal efficiency and adsorption capacity were 95.26%,31.75 mg/g.The structure of the composites was characterized by SEM,EDS,FT-IR,XRD,XPS and BET.At the same time,the adsorption process was explored.The adsorption process was combined with a quasi-second-order kinetic model,which belongs to chemical adsorption.According to Langmuir isothermal adsorption model,the adsorption process belongs to monolayer adsorption.It is proved that it can adsorb phosphate successfully and has a good effect of phosphorus removal.Finally,the effects of the dosage of La-SiO₂/SA,p H value of the solution and coexisting ions on the phosphorus removal rate were discussed.It was concluded that when the dosage was1.5 g/L,the removal rate was the highest.The removal efficiency of La-SiO₂/SA is better under neutral conditions.In the solution of the reaction system,the presence of NO₃^-and Cl^-ions has a weak influence on the removal efficiency,while HCO₃^-and SO₄^2-ions have a greater influence on the removal efficiency.In order to further improve the phosphorus removal ability of the composites,the lanthanum functionalized silica aerogel microspheres sodium alginate/polyvinyl alcohol composite(LA-SiO₂/SA/PVA)was prepared by introducing PVA into the above system.When the optimal ratio of SA/PVA to SiO₂ aerogel microspheres was 1:3,the optimal cross-linking agent concentration was 7%,and the optimal cross-linking time was 12 h,the maximum removal efficiency and adsorption capacity were 98.94%and 32.98mg/g.La-SiO₂/SA/PVA was characterized by SEM,EDS,FT-IR,XRD,XPS,BET,etc.It was found that after adding PVA,the composite material had a good network structure,and the specific surface area increased to 135.1878 m²/g.The adsorption process was combined with a pseudo-second-order kinetic model,which belongs to chemical adsorption.According to Langmuir isothermal adsorption model,the adsorption process belongs to monolayer adsorption.The adsorption-desorption cycle test shows that the composite has excellent stability and resistance.In conclusion,the two lanthanum-functionalized silica aerogel microsphere composites prepared in this study provide a valuable solution for phosphorus removal in wastewater due to their simple preparation,environmentally friendly and efficient and stable phosphorus removal properties,and have broad application prospects.