Influences Of Organic Chemicals From Copper Solvent Extraction On Adsorption Of Microorganisms To The Sulfide Minerals

During copper solvent extraction process,the organic phase is entrained and dissolved in the raffinateand contaminates the site of bioleaching with the raffinate recycling,resulting in leaching efficiency reduced.In this thises,the membrane permeability and potentialof cells of A.ferrooxidans,A.thiooxidans and L.ferrooxidans were analyzed by measur:ing the fluorescence intensity to characterize the inhibition mechanism of cells metabolism under the stress of the organic chemicals.The influenceof the extraction organic chemicals on the chemical composition of cells surface was studiedby Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS),also,the influence on the cells ?-potentialand contact angle was studied.More attentions were paid to the attachment of bioleaching microorganisms to the sulfide minerals.With the increase of LIX984N concentration,the growth of cells was inhibited increasingly.Both cells of A.ferrooxidans and A.thiooxidans delayed 24h to reach their stable growing,and L.ferrooxidans delayed 100h when LIX984N volume concentration was 5%(v/v).L.ferrooxidans was more sensitive to organic phase than A.ferrooxidans and A.thiooxidans.The membrane permeability for A.ferrooxidans,A.thiooxidans and L.ferrooxidans increased by 63%,49.6%,77.4%,respectively,when the cells were in contact with 1ml LIX984N for 60min.The influence of organic chemicals on the membrane potential presented almost the same pattern with the membrane permeability.Increasing of membrane permeability and decreasing of membrane potential explained the inhibition of cells growth to some extent.FT-IR spectra showed that many kinds of group,like CH,CH,CH3,NH,NH2?NH3,COOH and CONH,presented at thebacterial surfaces.The strength of absorption peaks of some groups have changed under the impact of 5.0%(v/v)LIX984N-containingorganic chemicals,especially the peak of 886cm-1,which was attributable to polysaccharide,significantly enhanced for A.ferrooxidans and A.thiooxidans.XPS uncovered that C,O,N elements at the bacterial surface accounted for imore than 99%,but P,S,Fe only about 1%.For A.ferrooxidans and L.ferrooxidans the relative proportions of polysaccharide and protein increased while lipiddecreased.However,for A.thiooxidansthe relative proportions of protein and lipid increased but polysaccharide decreased.The cell surface ?-potential of A.ferrooxidans,A.thiooxidans and L.ferrooxidans reduced with increasing of solution pH.The organic chemicals reducedthe electronegativity of cell surface.The ?-potential and isoelectric point increased with increasing of LIX984N concentration.With increasing of LIX984N concentration to 5.0%(v/v),the isoelectric point for A.ferrooxidans,A.thiooxidans and Lferrooxidans increased to about pH1.5,pH4,pH3.75,respectively.The organic chemicals enhanced the hydrophobicity of cells.Comparing with the control,the contact angles increased from 21.17° to 25.4° for A.ferrooxidans,22.3° to 27.8° for A.thiooxidansand 38.9° to 87.03° for L.ferrooxidans under the impact of 5.0%(v/v)LIX985N-containing organic chemicals.The cells attachment to the chalcopyrite ores was studied.The results showed the adsorption rate rosesharply at the initial stage then reached equilibrium rapidly.The adsorption equilibrium time for A.ferrooxidans and A.thiooxidans was 8 min and for L.Ferrooxidansonly 2 min.Pseudo second-order kinetics fitted the adsorption well.The attachment process was in agreement with the chemisorption mechanism.The rate constantfor bacterial sorption increased as Lferrooxidans>A.ferrooxidans>A.thiooxidans.