Biomineralization of Precious Metals

Abstract

In model tests, the kinetics and the possibility of concoction and biogenesis of ultradisperse forms of Au, Pd, and Pt in different physical and chemical conditions were examined. Studied biosorbents included peat, humic acids, nonhydrolyzed residue, and microscopic fungi in whole extract gold at 86–99 %, palladium at 89–95 % from chloride solutions, and platinum at 73–87 %. The maximum rate of extraction of Pd and Pt from solution by Penicillium canescens Sopp. biomass at different pH values was observed in sour solutions (pH 1–2) to be 16 and 47 mg/g of an element, respectively. The maximum rate of extraction of Au (to 24 mg/g) by fungic biomass was observed in subacidic solutions (pH 4–5). Palladium and platinum from chloride solutions were extracted from microfungi at rate of 87–95 % at optimum acidity of solution, with gold to 99 %. Using scanning electronic microscopy, the Pd and Pt distribution over the entire mycelium surface was established. The sorption process of precious metals by a fungic cell wall proceeded differently: the interaction process of ionic Au with an organic matrix continues up to the formation of metal nanoparticles, on which gold units are further formed, whereas the interaction of Pd and Pt stops at the sorption stage. It is thought that the biomineralization mechanisms of precious metals are caused by several reactions, including ion exchange, complex formation, and oxidation–reduction.