Microbial recovery of palladium by baker's yeast through bioreductive deposition and biosorption

Abstract

A microbial method using baker's yeast (Saccharomyces cerevisiae) was developed to collect aqueous Pd(II) ions through bioreductive deposition and biosorption at room temperature. Resting cells of S. cerevisiae reduced 1.0 mol/m3 aqueous Pd(II) ions in a Na2PdCl4 solution to metallic Pd(0) at pH 7.0 within 60 min when formate was provided as the electron donor under anaerobic conditions. Palladium nanoparticles were deposited on the surface of S. cerevisiae cells. The yeast cells also exhibited an excellent ability to collect Pd(II) ions from a 1.0 mol/m3 aqueous solution at pH 1.0 within 30 min under air. The baker's yeast was also applied to the effective recovery of aqueous Pd(II) ions in 1000–2000 mol/m3 HNO3 solutions (pH −0.3 to 0.0). When processing electroplating solutions, the yeast cells were able to selectively collect soluble Pd(II) at pH 0.0–0.8 within 60 min. Our proposal of using commercially available baker's yeast as a biosorbent enables rapid and efficient recovery of soluble palladium over the pH range − 0.30 to 7.0.