PRODUCTION OF HYDROLYZABLE INSOLUBLE TANNIN AND TREATMENT OF WASTE FLUID WITH THE INSOLUBLE TANNIN

摘要

PURPOSE:To obtain insoluble tannin capable of adsorbing heavy metals using many kinds of hydrolyzable tannins naturally present in much quantity as a raw material and to recover heavy metals by efficiently adsorbing heavy metals in a waste fluid using the soluble tannin. CONSTITUTION:A hydrolyzable tannin powder is dissolved in aqueous ammonia and the resulting solution is mixed with an aqueous aldehyde solution to form a precipitate which is, in turn, heated to be mixed with mineral acid. The obtained reaction mixture is filtered to produce insoluble tannin as a heavy metal element adsorbent insoluble in both of water and an acid or alkali. Since the polyphenolic hydroxyl group of tannin becomes a functional group to form a chelate compound along with heavy metal elements, the insoluble tannin shows high adsorbing capacity to heavy metal elements.