Influences Of Light And Galvanic Reactions On Microbial Oxidation Of Sphalerite

In recent years,the interaction between microorganisms and sulfide minerals which produced Acid Mine Drainage?AMD?and Acid Rock Drainage?ARD?has attracted wide attention.Among the sulfides,sphalerite,as a common zinc sulfide mineral,provides almost all the metal zinc in the world.At present,the techniques of zinc extraction mainly include Roast-Leach-Electrowinning Process?RLE?,Pressure leaching,Ferric leaching and Bioleaching.The dissolution kinetics and the changes of Fe,S and other elements in the process of microbial leaching have been further studied.However,the ore composition is generally complex and often a mixture of various minerals in the real life.And the galvanic reaction caused by differences of resting potential between different minerals cannot be ignored.The changes of morphology and secondary precipitation under galvanic reaction should be further studied.At the same time,sphalerite is a kind of typical semiconductor mineral.Photo-electrons will occur when stimulated by light.And this phenomenon have an influence to the sphalerite-Acidithiobacillus ferrooxidans system which needs to pay attention.Based on this background,two experiments were designed:?1?Influences of galvanic reaction on the interaction of Acidithiobacillus ferrooxidans and sphalerite;?2?Influences of light on oxidation of sphalerite by Acidithiobacillus ferrooxidans.A variety of modern technologies were used to explore the chemical oxidation and microbial oxidation of sphalerite in the different conditions.This paper observed the amounts of bacteria,solution chemistry indexes,surface morphology,secondary precipitations and surface chemistry changes in the reaction process.The first experiment results showed that the galvanic cell reaction would promote the oxidation of mineral with lower electrostatic potential,and produce secondary precipitation such as elemental sulfur,jarosite and iron phosphate when bacteria were present.The second experiment results showed that Acidithiobacillus ferrooxidans promoted the leaching of sphalerite obviously.It iwas also found that oxidation of Fe²⁺mainly occurred on the surface of bacteria,while Zn²⁺were passively released.And light could promote the growth and reproduction of microorganisms and slow down the corrosion of sphalerite to some extent.XPS analysis of the sphalerite surface revealed the transformation pathway of sulfur as S^2-/S₂^2-?S_n^2-/S⁰?SO₃^2-?SO₄^2-in chemical and microbial leaching systems.In the chemically leaching process,the contents of S_2-and S₂^2-on chemically leached surface in the light condition were much lower than that in the dark.However,light restrained the microbial oxidation of sulfur in the microbial leaching of sphalerite.Elemental sulfur was observed as intermediate phase,and jarosite was the end phase during the oxidation process of sphalerite.This work may deepen understanding of the mechanism of sphalerite microbial oxidation and assist on hydrometallurgical applications of sulfide ores or mine environmental remediation.Based on the analyses,the mechanism of chemical oxidation and microbial oxidation of sphalerite was improved in this paper.The mechanism could provide a reference for the improvement of hydrometallurgy and biological metallurgy processes,supplement the geochemical process of Fe and S elements,and offer a basis for the treatment and prevention of acid mine wastewater.