CHARACTERIZATION OF ARGENTOJAROSITE FORMED FROM BIOLOGICALLY OXIDIZED Fe3+ IONS

KEIKO SASAKI, MASAMI TSUNEKAWA & HIDETAKA KONNO
Faculty of Engineering, Hokkaido University, Sapporo 060, Japan

Abstract

Argentojarosite [AgFe3(SO4)2(OH)6] was synthesized without by-products at ambient temperatures from Fe3+ ions formed from Fe2+ ions by the iron-oxidizing bacteria Thiobacillus ferrooxidans. The product was characterized using X-ray- fluorescence (XRF) analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse- reflectance infrared Fourier-transform spectrometry (DRIFTS), inductively coupled plasma - atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). We found, using XRD, DRIFTS, and chemical analysis, that argentojarosite was formed from Fe3+ ions oxidized both biologically by T. ferrooxidans and chemically by H2O2. Differences were noted in the morphologies and intensities at two 3 (SO42-) bands of DRIFTS between biological and chemical products, but there is no major difference in chemical compositions, chemical species and XRD patterns. It is likely that the extracellular substances (secretions) from bacteria take part in the aggregation of the argentojarosite formed.

Keywords: argentojarosite, Thiobacillus ferrooxidans, inorganic synthesis, morphology, biological oxidation, biomineralization.