Preparation Of A Porous Silica-Based CeO₂/SiO₂ Adsorbent And Its Adsorption Behavior For Fluoride And Iodate

The composition of radioactive waste water produced by nuclear industry is complex,and the presence of fluoride and iodate poses a potential threat to human health and environmental safety.Therefore,it is necessary to take appropriate measures to remove fluoride and iodate from radioactive waste water.In this study,cerium oxide was loaded into silica channel by vacuum impregnation to synthesize CeO₂/SiO₂adsorbent,and the synthesized adsorbent was characterized by SEM,XRD and FT-IR.The results showed that cerium oxide was successfully immobilized onto the silica support,and the synthesized adsorbent was porous particles with a large specific surface and good stability.By infrared spectrum and Zeta potential analysis,the adsorption mechanism of CeO₂/SiO₂ adsorbent included the anion exchange and electrostatic interaction.The experimental results of the static adsorption showed that the calcination temperature and calcination time of CeO₂/SiO₂ could affect the adsorption of fluoride and iodate,and the adsorption capacity of fluoride and iodate decreased with the increase of the calcination temperature and calcination time.The optimum pH value of the fluoride adsorption was about 2.5.However,the solution pH had less effect on the adsorption of iodate.The adsorption of fluoride and iodate on CeO₂/SiO₂could reach equilibrium within 15 min and 1 h,respectively,and the saturated adsorption capacity could reach 2.44 mmol/g and 0.26 mmol/g,respectively.The adsorption processes presented a good fit to the pseudo-second-order kinetic mode and Langmuir model,which indicated that the adsorption of fluoride and iodate on CeO₂/SiO₂ was the chemisorption type and monolayer adsorption on a homogeneous surface.Due to competitive adsorption,coexisting anions such as SO₄^2-,H₂PO^4-,and PO₄^3-,etc.had different effects on the adsorption of fluoride and iodate.CeO₂/SiO₂ adsorbent had the excellent desorption property and reusability.The desorption efficiency of fluoride-loaded CeO₂/SiO₂ and iodate-loaded CeO₂/SiO₂ could reach about 95%and 83%,respectively,by using NaOH solution as desorption agent.The dynamic adsorption experiment of iodate showed that the column efficiency could reach90.96%,and the breakthrough curve was fitted well by Thomas model.From the above results,it can be seen that the CeO₂/SiO₂ adsorbent is expected to be applied to the efficient removal of fluride and iodate in radioactive wastewater.