Recovery of Precious Metals Using Microalgae Waste

Abstract

Katsutoshi Inoue, Kanjana Khunathai, Hidetaka Kawakita, Keisuke Ohto, Minoru Kurata, Hiroaki Fukuda and Kinya Atsumi

From waste residue of microalgae after extracting biofuel, some novel adsorption gels were prepared for the recovery of precious metals such as gold, palladium and platinum. The adsorption gel for gold was prepared in a simple manner by treating in boiling concentrated sulfuric acid. Although the feed material, the microalgae waste itself, was found to selectively adsorb gold(III), palladium(II) and platinum(IV) from hydrochloric acid solution over base metals such as copper(II), nickel(II) and so on, the adsorption of gold(III) was dramatically enhanced by the treatment using boiling concentrated sulfuric acid; it was recovered as metallic gold particles. In order to improve the adsorption behavior for palladium (II) and platinum (IV), some chemically modified microalgae gels were also prepared by immobilizing some functional groups such as dithiooxamide, polyethyleneimine and trimethylamine. On the basis of the basic investigation about the adsorption behaviors of these biosorbents, recovery of precious metals was investigated also from actual leach liquor of waste printed circuit boards of electronic devices using these adsorbents in order to verify their effectiveness for practical application.

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