バイオマス廃棄物の有効利用による有害金属の除去および有価金属の回収 [in Japanese] Development of the Technology for Removing Toxic Metals and Recovering Valuable Metals by the Effective Use of Biomass Wastes [in Japanese]
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The technology for removing toxic metals such as lead, cadmium, arsenic and radioactive elements from environment as well as recovering valuable metals such as precious metals from various wastes was developed by effectively using various natural products and biomass wastes.<BR>The natural products employed in the present work are pectic and alginic acids contained in fruits like orange and apple and in brown seaweeds, respectively. These acidic polysaccharides behave as natural chelating polymers for cationic metal ions such as lead(II), copper(II) and iron(III). On the other hand, those loaded with high-valence metal ions such as iron(III) selectively adsorb anionic species of arsenic(III and V) according to ligand exchange reactions. On the basis of these adsorption behaviors of pectic acid, adsorption gel was directly prepared from orange waste at cheap cost to prove the effective removal of arsenic from actual acid drainage.<BR>Another adsorption gel was prepared from persimmon waste, which exhibited selective adsorption to thorium and uranium over rare earth elements. It is expected to be used for the removal of these radio active elements from environment including tailings of rare earth ores.<BR>Lignin contained in wood wastes in large amount was extracted as lignophenol according to the phase separation method developed by Funaoka and new adsorption gel was prepared by crosslinking. The gel exhibited interesting behavior for gold. Elemental gold was directly recovered from gold containing hydrochloric acid solution, which was attributed to the reductive function by phenol groups rich in this gel.<BR>Novel adsorption gel was also prepared from waste newspaper paper by immobilizing primary amino groups. This gel exhibited high selectivity to copper(II) and chromium(VI) in pH region and to precious metals, gold(III), palladium(II) and platinum(IV), in the adsorption from hydrochloric acid.<BR>All of the adsorption gels developed in the present work exhibited more excellent adsorption behaviors than conventional adsorbents like commercially available ion exchange resins and activated carbon.
Shigen-to-Sozai 123(2), 59-67, 2007-02-25
The Mining and Materials Processing Institute of Japan