Evolvement Of Surface Property Of Extracellular Polymeric Substances Of A.ferrooxidans With Culture And Time

Acidithiobacillus ferrooxidans is a main strain of bacterium in the field of bioleaching in the current research, it has important industrial application value in biological metallurgy, treatment of industrial wastewater containing heavy metal materials, pretreatment of sulfide ore containing arsenic and coal desulfurization. Researches and leaching mechanism between microbial and mineral interaction is the frontier fields of biological metallurgy, EPS is closely related with mineral surface chemistry, mineral electrochemical mechanism and microbial chemistry. EPS plays an important role in the process of Acidithiobacillus ferrooxidans absorbed to the mineral surface. Therefore, the study of Acidithiobacillus ferrooxidans's EPS surface properties and its evolution has very important significance of clarifying the process of bioleaching and its absorption mechanism.In this paper, through cultivation A.f were cultured in three different mediums:(A) 9K medium, (B) 9K medium containing different concentrations of Cu2+ ions, (C) 9K media without Fe but containing 1% chalcopyrite, and collected bacteria samples in different growth stages, with the method of ultrasonic-centrifugal to extract EPS of bacteria, and used the method of phenol hydrate-sulfuric to testing the concentration of polysaccharide in EPS as a representation of the concentration of EPS, then respectively using spectrophotometer, FT-IR and atomic absorption spectrometry to testing and research the concentration of EPS, surface properties and the concentration of copper and iron ion absorbed in EPS, to reflect A.f EPS's surface properties' evolution through different mediums and times.The results of the research indicate that:(1) The function groups of EPS components almost do not essential change under the conditions of different growth periods and culture media, but its constituents contents will appear corresponding change, bacteria produce more EPS rather than changing the essential ingredients of EPS to resist the influence of disadvantageous factors and to adapt the growing environment. (2) The concentration of EPS produced by bacteria rapid growth firstly, and then slowly decreases, finally tend to be a higher steady value. Generally speaking, total EPS amount by bacteria is (B)>(C)>(A), with the increases of initial Cu2+concentration, the concentration of EPS increases correspondingly, Cu2+can promote bacteria to produce more EPS, particularly, EPS amount increases rapidly when the concentration of Cu2+ions is more than the tolerable concentration of bacteria. (3) In the three different cultivate medium, the adsorption amount of TFe in EPS is (C)>(B)>(A) and amount of Cu2+in EPS also is (C)>(B)>(A), at the same time, amount of TFe in EPS always is much more than that of Cu2+ (4) With the increase of the concentration of Cu2+during bioleaching chalcopyrite, a number of EPS is produced and can adsorb jarosites to form weak ion diffuse barrier layer on chalcopyrite, inevitably inhibited the effect of the leaching of chalcopyrite, which is responsible for ultimate passivation of chalcopyrite.