Bioleaching of chalcopyrite with different crystal phases by Acidianus manzaensis

Bioleaching of chalcopyrite with different crystal structures (α-phase,β-phase and γ-phase) by Acidianus manzaensis was comparatively studied by synchrotron radiation based X-ray diffraction (SR-XRD) and S K-edge X-ray absorption near edge structure (XANES) spectroscopy. The α-phase,β-phase and γ-phase chalcopyrite was prepared by heating original chalcopyrite at 583, 773 and 848 K, respectively. Bioleaching results showed that [Cu^2+] in the leaching solution of α-phase,β-phase,γ-phase and original chalcopyrite after 10 days of bioleaching was 1.27, 1.86, 1.43 and 1.13 g/L, respectively, suggesting that β-phase had a better leaching kinetics than others. SR-XRD and XANES results indicated that jarosite and chalcopyrite were the main components in the leaching residues in all cases, and elemental sulfur formed in the early stage of bioleaching. While for β-phase and γ-phase chalcopyrite during bioleaching, bornite was produced in the initial stage of leaching, and turned into chalcocite on day 6.

Relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture at 65°C

The relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleachingby mixed thermophilic Archaea culture(Acidianus brierleyi,Metallosphaera sedula,Acidianus manzaensis and Sulfolobusmetallicus)at65°C was studied.Leaching experiments showed that the addition of activated carbon could significantly promote thedissolution of chalcopyrite for both bioleaching and chemical leaching.The results of synchrotron-based X-ray diffraction,ironL-edge and sulfur K-edge X-ray absorption near edge structure spectroscopy indicated that activated carbon could change thetransition path of electrons through galvanic interactions to form more readily dissolved secondary mineral chalcocite at a low redoxpotential(?400mV)and then enhanced the copper dissolution.Jarosite accumulated immediately in the initial stage of bioleachingwith activated carbon but copper dissolution was not hindered.However,much jarosite precipitated on the surface of chalcopyrite inthe late stage of bioleaching,which might account for the decrease of copper dissolution rate.More elemental sulfur(S0)was alsodetected with additional activated carbon but the mixed thermophilic Archaea culture had a great sulfur oxidation activity,thus S0waseliminated and seemed to have no significant influence on the dissolution of chalcopyrite.

Effect of the surface microstructure of arsenopyrite on the attachment of Sulfobacillus thermosulfidooxidans in the presence of dissolved As(Ⅲ)

Understanding bacterial adsorption and the evolution of biofilms on arsenopyrite with different surface structures is of great signific-ance to clarifying the mechanism of microbe-mineral interfacial interactions and the production of acidic mine drainage impacting the environ-ment.In this study,the attachment of Sulfobacillus thermosulfidooxidans cells and subsequent biofilm formation on arsenopyrite with different surface structures in the presence of dissolved As(Ⅲ)was studied.Arsenopyrite slices with a specific surface were obtained by electrochemic-al corrosion at 0.26 V.The scanning electronic microscopy-energy dispersion spectra analyses indicated that the arsenopyrite surface deficient in sulfur and iron obtained by electrochemical treatment was not favorable for the initial adsorption of bacteria,and the addition of As(Ⅲ)in-hibited the adsorption of microbial cells.Epifluorescence microscopy showed that the number of cells attaching to the arsenopyrite surface in-creased with time;however,biofilm formation was delayed significantly when As(Ⅲ)was added.

Fe/S oxidation-coupled arsenic speciation transformation mediated by AMD enrichment culture under different pH conditions

Arsenic(As)speciation transformation in acid mine drainage(AMD)is comprehensively affected by biological and abiotic factors,such as microbially mediated Fe/S redox reactions and changes in environmental conditions(pH and oxidation-reduction potential).However,their combined impacts on arsenic speciation transformation remain poorly studied.Therefore,we explored arsenic transformation and immobilization during pyrite dissolution mediated by AMD enrichment culture under different acidic pH conditions.The results for incubation and mineralogical transformation of solid residues show that in the presence of AMD enrichment culture,pH 2.0,2.5,and 3.0 are more conducive to the formation of jarosites and ferric arsenate,which could immobilize high quantities of dissolved arsenic by adsorption and coprecipitation.The pH conditions significantly affect the initial adsorption of microbial cells to the minerals and the evolution of microbial community structure,further infuencing the biodissolution of pyrite and the release and oxidation process of Fe/S.The results of Fe/S/As speciation transformation of the solid residues show that the transformation of Fe,S,and As in solution is mainly regulated by pH and potential values,which imposed significantly different effects on the formation of secondary minerals and thus arsenic oxidation and immobilization.The above results indicated that arsenic transformation is closely related to the Fe/S oxidation associated with pyrite bio-oxidation,and this correlation is critically regulated by the pH conditions of the system.