ADSORPTION BEHAVIOR OF METAL-IONS ON SOME CARBOXYMETHYLATED CHITOSANS

Monocarboxymethylated chitosan and N,N-dicarboxymethylated chitosans ( IDA-type chitosan) as well as diethylenetriaminepentaacetic acid-type chitosan (DTPA-type chitosan) were synthesized in order to investigate their adsorption behavior for metal ions. The adsorption of copper(II ) from 1 mol/dm(3) aqueous ammonium nitrate solution takes place in th e sequence of pH as follows: DTPA-type chitosan much less than IDA-typ e chitosan much less than monocarboxymethylated chitosan < chitosan. T he maximum adsorption of copper(Il) (mol/kg) on each adsorbent was IDA -type chitosan, 2.4; DTPA-type chitosan and original chitosan, 2.0; an d monocarboxymethylated chitosan, 1.7. The values for IDA- and DTPA-ty pe chitosan and the original chitosan were greater than that for comme rcial IDA-type chelating resin. Although the commercial IDA-type chela ting resin showed only poor selectivity for nickel, zinc and cobalt, D TPA- and IDA-type chitosans showed higher selectivity for these metals ; especially, the separation factor for Ni/Co by DTPA-type chitosan wa s as high as 10. Although the original chitosan and IDA-type chitosan exhibited poor selectivity for trivalent rare earths, DTPA-type chitos an showed excellent selectivity for light rare earths; the separation factors for Ce/La and Nd/Pr were 5.76 and 2.27, respectively.