Abstract
The effect of the surface microstructure and chemical speciation of chalcopyrite on the attachment behaviors of thermoacidophilic archaeon Sulfolobus metallicus was evaluated for the first time by using integrated techniques including epifluorescence microscopy (EFM) and sulfur K-edge X-ray absorption near edge structure (S K-edge XANES) spectroscopy, as well as scanning electron microscopy with energy dispersive spectrometry (SEM/EDS) and Fourier transform infrared (FT-IR) spectroscopy. In order to obtain the specific surface, the chalcopyrite slices were electrochemically oxidized at 0.87 V and reduced at −0.54 V, respectively. The EFM analysis showed that the quantity of cells attaching on the mineral surface increased with time, and the biofilm formed faster on the electrochemically treated slices than on the untreated ones. The SEM-EDS analysis indicated that the deficiency in energy substrate elemental sulfur (S0) in the specific microsize of local defect sites was disadvantageous to the initial attachment of cells. The XANES and FT-IR data suggested that the elemental sulfur (S0) could be in favor of initial attachment, and surface jarosites inhibited the adsorption and growth of S. metallicus. These results demonstrated that not only the surface microstructure but also the chemical speciation defined the initial attachment behaviors and biofilm growth of the extreme thermophilic archaeon S. metallicus.
Highlights
Bioleaching is as an eco-friendly and cost-effective way to extract the precious metals from low-grade ores, and was recognized as one of ten top world challenge technologies by Scientific American in 2011 [1]
A1 represented the beginning of the oxidizing reaction on the surface of chalcopyrite and non-stoichiometric amorphous products that lacked Fe/S according to Price et al [6] (see Equation (1))
The results of EDS showed that the initial attachment of cells observed the following order for both the creviced and flat areas: chalcopyrite treated at 0.87 V > original chalcopyrite > chalcopyrite treated at −0.54 V, indicating that the bacteria cells preferred S species on the mineral surface
Summary
Bioleaching is as an eco-friendly and cost-effective way to extract the precious metals from low-grade ores, and was recognized as one of ten top world challenge technologies by Scientific American in 2011 [1]. In this method, bioleaching microbes oxidize ferrous ion (Fe2+ ). S0 into ferric iron and sulfuric acid that attack and dissolve the rocky materials and release the metals This process could be detrimental to the environment due to the formation of acid mine drainages (AMDs) in the sites of abandoned ores or tailings if it is not constrained and prevented. There have been few studies on this topic [3,4,5,6,7,8], and the microbe-mineral interfacial interaction is still unclear, especially for the case of iron- and sulfur-oxidizing archaea, whose cellular structure and physiological temperature are quite different from the mesophilic or moderate thermophilic bioleaching bacteria
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