Studies On The Isolation And Identification Of A. Ferrooxidans And Its Interaction With Sulfide Ores

The attachment at the interface between microbe and mineral, beinghighlighted by the researchers in the world, is both the primary step oftheir interanction and the key procedure in bioleachiong.Acidithiobacillus ferrooxidans (A. ferrooxidans) is one of the mostimportant and lucubrated bacteria in bioleaching. This paper presents theisolation and characterization of two A. ferrooxidans, preparation andphysiological-biochemical characterization analysis of jarosite during A.ferrooxidans growth and evaluation of adsorption phenomena of thesetwo strains on sulfide minerals, and analysis of enthalpy variation duringadsorption processes and extracellular polymers (EPS) on the surface ofsulfide minerals.Two stains were isolated from the mining tailing in Tong Shankou,Hubei province, China. They were both identified as strains of A.ferrooxidans and named as A. ferrooxidans TSK-1 and A. ferrooxidansTSK-2, respectively. Comparative study on growth of these two strains inbetween ferrous sulfate-containing and sulfur-containing cultures showsthat ferrous sulfate effects faster but for shorter time and provides lessenergy than sulfur.Jarosite prepared by bacterial and chemical methods have beenanalyzed. More bacteria and less precipitation can be collected after40-46h A. ferrooxidans is inoculated. Both the increase of ferrous ironsand the rise of pH can promote the product of jarosite. No precipitation isobserved when pH is lower than 1.60. Because of the smaller andaequaliser particle and smoother outer surface, the jarosite prepared bybacterial method is more suitable in material field than that prepared bychemical method.The attachment of A.ferrooxidans on pyrite appears as a fastprocedure. The maximum adsorption occurs at 30 min after inoculation ofA. ferrooxidans into pyrite suspension, at 90 min. While in chalcopyritesuspension, the maximum adsorption appears at 45 min and theadsorption equilibrium at 90 min and adsorption begins to decrease at 120min. Due to the difference of crystal construction and surface characteristics among pyrite, chalcopyrite and sphalerite, display amaximum adsorption amount on pyrite and a minimum value onsphalerite. Augmenting the mineral and bacterial concentration andvibrating appropriately can enhance the adsorption amount of A.ferrooxidans on pyrite. 30℃and pH 1.8-3.0 is the most suitable conditionfor the growth and metabolism of A. ferrooxidans, and so as itsattachment on pyrite. Compared with other particle sizes, 200 mesh ismost fit for bacterial attachment. SEM pictures show that A. ferrooxidanscan attach on pyrite surface firmly, and the bacteria attached on pyritegrains is much more than on slices.The influences of condition factors to reaction heat duringattachment process agree well with that in attachment amountexperiments. A. ferrooxidans cultured in different mediums with differentcontents of Extracellular Polymers (EPS) creates different heat ofreaction attaching on the surface of mineral. Bacteria cultured with pyritehaving the most EPS creates the biggest heat of reaction, which provesthe important role of EPS in the process of attachment.A saturation of heat of reaction in the process of L-cysteineattachment on pyrite occurs with the increace of the concentration ofL-cysteine, which is Langmuir monomolecular layer attachment. Theattachment of glucose on pyrite is similar to mannose: heat release andthe max heat peak appear quickly, and the heat of reaction increasesconstantly with the increace of the glucose and mannose, which is notLangmuir monomolecular layer but multilayer attachment. FTIR analysisconfirms that the attachment of L-cysteine on pyrite is chemicalattachment while glucose and mannose belong to physical attachmen.