Adsorption behavior of Diatomite-KH560 for iodide in water
An composite adsorbent,Diatomite-KH560 was prepared by loading γ-(2,3-epoxy propoxy)pro-pytrimethoxysilane(KH560)on the surface of cheap and easily obtained diatomite,and its high-efficiency adsorption performance for iodide in aqueous solution was investigated.KH560 Was loaded on diatomite by immersion and hydrolysis,and contact time,temperature,pH,initial concentration and coexisting ions were investigated to evaluate the adsorption performance of Diatomite-KH560 for iodide.The result showed that Diatomite-KH560 with mild preparation conditions has high thermal stability,and the modification amount of KH560 is more than 13.3％.It takes a long time for Diatomite-KH560 to reach adsorption equilibrium for iodide,which may be controlled by several factors such as the diffusion of iodide in aque-ous solution and the adsorption reaction rate on the adsorbent surface.The rate-controlling step is trans-formed into chemical adsorption process with the increase of temperature.In weak acid environment,the epoxy group on Diatomite-KH560 is protonated,forming positively charged adsorption sites,which adsorbs iodide through electrostatic attraction.According to the anion composition characteristics of brine,the effect of high concentration of chloride ion and trace amount of bromide ion and sulfate on the adsorption of iodide was investigated.It was found that the adsorption capacity of Diatomite-KH560 on iodide remained at 0.63 mg/g when the initial Cl/I reached 2 500 times.On the basis of the characterization results of EDS and FTIR,combined with the molecular structure of KH560,Diatomite-KH560 may achieve highly selective adsorption of iodide through the protonation of epoxy groups.
iodideadsorptionprotonationcoexisting ion interference
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