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Removal of perchlorate ion in tap water with montmorillonite which modified with hexadecylpyridinium chloride (CPC-montmorillonite) was investigated by column chromatography. Almost all anions except Cl ion in a tap water containing 0.518 and 0.540 mg dm on average of perchlorate ion (ClO4) and bromate ion (BrO3), respectively, through the CPC-montmorillonite bed, are adsorbed at the beginning of the column experiment, whereas the Cl concentration in effluent immediately increases steeply. The anions exhibit breakthrough in the order of F, SO4, BrO3, NO3, Br and ClO4. These results suggest that the anion uptake on CPC-montmorillonite proceeds through anion-exchange process, and the anion affinity of CPC-montmorillonite becomes F < SO4 < BrO3 < NO3 < Br < ClO4. The ClO4 concentration in effluent solution passing through the CPC-montmorillonite bed falls below detection limits of ion chromatography up to 4,500 bed volumes (BV) at the feed solution rate of space velocity (SV) 15 h, thus the ClO4 ion in the tap water can be reduced to less than 0.025 mg dm of the target value under consideration as a standard of water-purity for tap water at Ministry of Health, Labour and Welfare of Japan. The ClO4 concentration increases gradually between 5,000 and 10,000 of BV and becomes nearly constant at above near 10,000 of BV. The ClO4 uptake amount on the column experiment can be estimated as 0.04 mmol g from the adsorption breakthrough curve of ClO4 ion. During 37 consecutive days of column experiment, 86 % of hexadecylpyridinium chloride molecules were eluted from an interlayer of CPC-montmorillonite and the basal spacing, (001) plane, of CPCmontmorillonite decreased from 4.05 nm to 2.11 nm.

Removal of Perchlorate Ion in Tap Water with Montmorillonite Modified with Hexadecylpyridinium Chloride