A Primilinary Study on Bio-oxidation of Galena by Acidithiobacillus ferrooxidans

A strain of Acidithiobacillus ferrooxidans(A.f.) isolated from the acid mine drainage(AMD) of the Dabaoshan mine and a mineral galena was used to study its bio-oxidation of galena.Experiments were designed to compare the differences between abiotic oxidation and bio-oxidation of galena at pH2.00 and 3.00 with or without Fe2+.The concentrations of cations such as Pb2+,As5+ and Cd2+,anion SO2-4 and pH values during the experiments were measured,the solid experimental results were analyzed with XRD,and changes in galena surface were investigated on a scanning electron microscope(SEM).The results showed that galena is easier to oxidize at pH2.00 than at pH3.00.The iron ions promoted the bio-oxidation of the galena for about 10 to 25 times.The pH values of the final solutions of the bio-oxidation and of the existence of iron ions are much lower than those of abiotic oxidation.The results also indicated that the precipitation of lead sulphates in the bio-oxidation preventet the direct bio-oxidation of galena,so that the bio-oxidation of galena may occur mainly in the "indirect" manner.Adding some alkaline substances in the acid mine drainage(AMD) can enhance its pH value and reduce its iron ion concentrations,so as to decrease the bio-oxidation rate of galena and reduce the production of heavy metallic ions.