The surface modification of kaolinite to introduce the adsorption sites for anionic species was reported. The introduction of an anion exchange site was as follows; intercalation of 2-aminoethanol into kaolinite by using dimethyl sulfoxide-kaolinite intercalation compound as a precursor and subsequent hydrochlorination of 2-aminoethanol-kaolinite in 1,4-dioxane. The hydrochlorination of 2-aminoethanol-kaolinite was confirmed by the increase in the basal spacing (0.2 nm, corresponding to the diameter of chlorine) and the appearance of the infrared absorption bands due to ammonium groups. The modified kaolinite adsorbed an anionic dye, tetrakis(p-sulfonatophenyl)porphyrin, from a N,N-dimethylformamide solution. Initial slope of the adsorption isotherm of tetrakis(p-sulfonatophenyl)porphyrin on the hydrochlorinated 2-aminoethanol-kaolinite was steep, showing strong adsorbate-adsorbent interactions. The gallery height after the adsorption of tetrakis(p- sulfonatophenyl)porphyrin was close to the thickness of the porphyrin ring, suggesting that tetrakis(p-sulfonatophenyl)porphyrin was intercalated as a monomolecular layer and that chlorine simultaneously deintercalated.
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