The Synthetic Of Porous Silicon Base Cerium Oxide Microspheres And Its Application In Removal Of Fluoride

In this paper,a new fluoride removal agent was prepared by using vacuum perfusion method and co-precipitation technology,and the hydrated cerium oxide was loaded onto porous silicon base microspheres.The removal of fluoride of adsorbents is improved,which can be used to treat wastewater containing fluorine in depth.The cerium salt is abundant,cheap and widely used in GuangXi.At the same time,it is easy to solid-liquid separation compared with cerium oxide powder.This preparation process does not require high temperature calcination,which can further reduce the cost of the preparation process.The prepared adsorbent was characterized by SEM,EDS,XRD,XPS,Zeta,BET,TG,FT-IR and verified that the hydrated cerium oxide was effectively loaded onto porous silicon base microspheres.The preparation conditions,adsorption property,adsorption mechanism,desorption and circulation of the adsorbent were systematically studied.The main results are as follows:（1）It can be seen from the adsorption experiment of fluorine ions:ceriumchloride heptahydrate was used as the source of cerium,silicon dioxide microspheres/cerium oxide mass ration 1:1,the hydrated cerium oxide was loaded onto porous silicon base microspheres by using vacuum perfusion method and co-precipitation technology.The optimum preparation condition for porous silicon base cerium oxide adsorbent is pH 9-10,the synthesis temperature 75℃,maintenance time 15h,drying temperature 60℃ and the specific surface area is 93.90 m2/g.（2）Optimum conditions for adsorption of porous silicon base microspheres adsorbent:pH=3,liquid-solid ratio is 0.15g/100mL and the adsorption time is 120min.The adsorption process was found to fit well the pseudo-second-order kinetic model,intra-particle diffusion model and Langmuir isothermal model,with a maximum adsorption capacity of 273.97mg/g.According to thermodynamic analysis,the adsorption process is a spontaneous process of endothermic entropy increase.（3）The competitive adsorption capabilities are as follows Cl-<NO3-<SO42-<PO43-by studying the influence of coexisting ions on adsorption process,which Po43-and SO42-have great influence and the adsorption capacity decreases 10.59mg/g and 5.77 mg/g,respectively.In addition,there are still 84.16%and 84.51%fluorine removal percentage in real seawater and tap water.The desorption and regeneration experiment showed that the desorption efficiency reached 97.73%when the concentration of NaOH was 0.5 mol/L.The adsorbent still has an adsorption capacity of 19mg/g for fluorine ions after four cycles,which shown that CeO₂/SiO₂ adsorbent could be reused.（4）This experiment used column test to investigate the dynamic breakthrough curves of CeO₂/SiO₂ adsorbent on fluorine ions.The filling column height was 0.5cm,1cm and the dynamic adsorption capacity was 47.87mg/g,56.32mg/g.Thomas model was used to fit the experimental data.Adsorption mechanism was analyzed by IR,Zeta potential,XPS,etc.The adsorption process of fluorine ions by CeO₂/SiO₂ adsorbent is not only adsorption but also ion exchange.