The in situ relevance of micro- structure and electrochemical properties of chalcopyrite to adsorption of thermoacidophilic bioleaching Archaea Acidianus manzaensis was studied. In this study, the electrochemical behavior of chalcopyrite was first investigated by cyclic voltammetry (CV) to get suitable initial reduction and oxidation potentials, at which electrochemical corrosions of chalcopyrite for several time were performed, respectively, to get specific surface micro-structures. The specific adsorption of A. manzaensis on the electrochemically corroded chalcopyrite surface was then comparatively studied. The changes of microstructure and chemical composition/speciation on the surface of chalcopyrite before and after electrochemical treatment and bio-adsorption was characterized by scanning electron microscopy/electron dispersive spectroscopy (SEM/EDS), and synchrotron radiation-based X-ray diffraction (SR-XRD) and Fe, Cu K-edge X-ray absorption near edge structure (XANES) spectroscopy. The results showed that the suitable initial oxidation and reduction of chalcopyrite electrode were at 0.67 V for 1h and -0.54 V for 10 min, respectively. After treated at 0.67V the surface of chalcopyrite became Cu-deficient with a composition of CuFe1.02S2.15, and bornite (Cu5FeS4) was detected. While after treated at -0.54V, the surface became Fe/S-deficient, with a composition of CuFe0.33S0.81, and a mass of chalcocite and some covellite were detected. Comparing to the original chalcopyrite, the adsorption capacity of A. manzaensis was increased on the surface of oxidation-treatment at 0.67 V, and decreased on the surface of reduction-treatment at -0.54 V. It clearly demonstrates the bornite-containing copper deficient chalcopyrite surface was more preferably adsorbed, whereas the chalcocite-containing Fe/S deficient chalcopyrite surface was less adsorbed by A. manzaensis, indicating the dependence of the specific adsorption of A. manzaensis upon the secondary minerals as well as Fe/S availability in the microstructure of chalcopyrite.

The bioleaching experiments of chalcopyrite were conducted with single and mixed mesophiles (30 °C) and moderate thermophiles (45 °C) and extreme thermophile (65 °C), respectively, and analyzed by synchrotron radiation (SR) based X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) spectroscopy. The results showed that the copper extraction of chalcopyrite could be significantly promoted by bioleaching microorganisms, and the promotion effects for both the mixed cultures grown at different temperature and the different cells grown at the same temperature were significantly different. The surface of chalcopyrite after bioleached by the mixed or sole cultures are serious corroded and became complicated. More S0 was found to form in the sole cultures of specific iron-oxidizing microorganism L. ferrooxidans and L. ferriphilum and sulfur-oxidizing microorganisms A. thiooxidans and A. caldus cultures. Jarosite and secondary minerals (chalcocite and covellite) were detected for the mixed cultures and sole cultures of iron/sulfur-oxidizing microorganisms. The evolution of chalcocite and covellite were just relevant to the potential of leaching solution, no matter which cultures were used, where chalcocite could be formed at Eh value less than 500 mV and then converted to covellite at Eh value ~550 mV.

This article presents the progress on characterization of the interfacial interaction between sulfur oxidizing microbes and sulfide minerals by using of synchrotron radiation-based techniques including S/Fe/Cu X-ray absorption near-edge structure spectroscopy (XANES), X-ray Diffraction (XRD), micro-X-ray fluorescence (μ-XRF) mapping and micro-scanning transmission X-ray microscopy (μ-STXM) imaging, together with other accessory approaches such as SEM/EDS, Raman spectroscopy, FT-IR spectroscopy, and electrochemical methods as well as comparative proteomics methodology.

The surface properties and iron distribution of Acidianus manzaensis YN25 grown on four different energy substrates (chalcopyrite, pyrite, S0, and Fe2+) were comparatively studied. The results showed different growth and absorption features of A. manzaensis grown on different energy substrates. Results also showed that Zeta potentials, adsorption forces and cell surface acid-base properties were significantly influenced by the growth condition. Studies based on FT-IR and UV-vis spectroscopy indicated that the differences in cell surface properties may result from the different amounts of proteins and iron distribution on the cell surface of A. manzaensis grown on different growth conditions. The SR-μ-STXM images showed that the cell surface densities of iron spread on the cells grown on chalcopyrite, pyrite, S0 or Fe2+ were 4.31×10-5 - 23.25×10-5 g/cm2, 4.43×10-5 - 20.24×10-5 g/cm2, 0.10×10-5 - 0.29×10-5 g/cm2, and 6.45×10-5 - 24.06×10-5 g/cm2, respectively, further indicating that the surface of A. manzaensis cells grown on chalcopyrite, pyrite and Fe2+ had an iron-contained compounds, which might be the reason why the surface of A. manzaensis cells grown on chalcopyrite, pyrite and Fe2+ carried weak positive charges at pH 2 while negative for the cells grown on S0.

This article presents as follows the most recent progresses of our group on in-situ characterization and evaluation of the molecular mechanisms of interfacial interaction of minerals and bioleaching microorganisms. (1) By studying the speciation transformation of iron/copper/sulfur on the mineral surface, the evolution of cell surface properties and EPS composition, the evolution of microbial community structure, and the evolution of expression of key oxidase genes during bioleaching, to characterize the adaptation process and therein the effects of it on the specific sulfur oxidation efficiency of bioleaching; (2) by in-situ characterization of the evolution of chalcopyrite surface microstructure, chemical speciation and the biofilm formation, to illustrate the specific adsorption and the relationship between cell growth/biofilm formation and the structure and speciation on the defect mineral surface; (3) by studying the utilization, transformation and activation of S0, which is one of the major intermediates during bioleaching, and the distribution of extracellular thiol groups and iron speciation, to evaluate in situ the sulfur activation mechanism; and (4) by comparative proteomics study of the extracellular and outmembrane proteins and looking up the genome sequence, to screen sulfur activation/transportation relevant proteins and genes.