Development of the Technique for Recovery and Purification of Lead and Arsenic in Water on Biomass Wastes.

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Alginic acid and pectinic acid are used as adsorbents for recovery of lead and arsenic. These were crosslinked not to dissolve in an alkaline solution. The crosslinking was carried out by two kinds of methods : one is the crosslinking by chloromethyl oxirane in an alkaline solution, and the other is the crosslinking by formaldehyde in hydrochloric acid. These resins were found to have a high selectivity for lead and ferric iron. Especially, ferric iron was adsorbed even at below pH 1, indicating that the crosslinked Fe/alginic acid and Fe/pectinic acid can be used as the adsorbents for arsenic. On the other hand, we synthesized a chitosan derivative introducing thiocarbamoyl groups to recover arsenic(III) being classified as "soft acid". Scince the thiocarbamoyl group is classified as "soft base", this chitosan derivative was expected as a selective adsorbent for arsenic(III). However, this chitosan derivative was not able to adsorbed arsenic(III) though this can selectively adsorbed mercury(II) over base metals such as ferric iron, nickel, cobalt, and zinc. Therefore, we determined to use the Fe/alginic acid and Fe/pectinic acid as adsorbents for arsenic. These metal-complex resins found to be a selective and effective adsorbent for arsenic(III, IV).