抄録
Insoluble clay-metal hydroxide conjugates with small swelling in water were synthesized. Iron or cerium hydroxides were immobilized electrostatistically in the innerlayer of the Na-montmorillonite with high dispersion. Clay+Mt(OH)n conjugate (Mt: Fe, Ce) were prepared by intercalating the colloid of metal hydroxide in the innerlayer of the clay. Clay+Mt→OH conjugates were prepared by introducing the metal ions in the clay through ion-exchange followed by hydrolysis of the metal ions in the clay. The intercalation of the metal hydroxides and the chemical state of the metals in the conjugates were evaluated by X-ray diffraction and X-ray absorption fine structure (XAFS) measurements. The conjugates showed mesoporous structure with high specific surface area around 85-150 m2/g. The conjugates adsorbed AsIII and AsV from the aqueous solutions of As2O3 and KH2AsO4. The Langmuir type adsorption isotherms for AsIII and AsV with a large value of Langmuir constant, K, were obtained in the Ce-conjugates (Clay+Ce→OH, Clay+Ce(OH)n), which indicated that the conjugates were effective for the removal of dilute arsenic. The adsorption capacity of the Clay+Ce→OH conjugate was superior to that of the Clay+Ce(OH)2 conjugate for dilute arsenic solution. The co-existing anions such as chloride, carbonate, sulfate and phosphate ions affected little on the removal of arsenic.
