Biooxidation Pretreatment Of Arsenric-bearing Refractory Gold Ores By Using Moderate Thermophiles

The acidithermophiles had been extensively studied in the last decade because they can endure the high temperature occur in the process of sulfide mineral bioleaching and has stronger leaching ability to leach sulfide mineral.The biooxidation pretreatment of arsenric-bearing refractory gold ores can release the Au contained in sulfide minerals that will result in increase of the Au recovery ratio at the flowing CN treatment.In this study,biooxidation pretreatment of arsenric-bearing refractory gold ores was researched by using moderate thermophiles. Firstly,the sample collected from Shandong,China were enriched and domesticated by arsenic refractory gold,then,biologic diversity of this sample was analyzed by using PCR-RFLP analysis.Secondly,impacts of different bacterial activating methods on the dearsenification were researched.In addition,the optimum bioleaching conditions of the bacteria including pulp density,arsenic-containing,inoculations,pH and temperature were measured by using orthogonal design test.At last,in order to enhance the bacteria's resistance ability against pulp density and increase the dearsenification ratio,a Cyanidium caldarium strain was isolated and added into the biooxidation pretreatment system,and the results indicated that make sense for increasing the dearsenification ratio.A mix culture of moderate thermophiles was enriched in the medium contained arsenric-bearing refractory gold ores as the exclusive energy sources.Community analysis of the mix culture was done.Analysis of restriction enzyme-digested 16S rRNA genes has revealed there was limited biodiversity in the mix culture in which the microflora appeared to consist of Leptospirillum ferriphilum and Acidithiobacillu caldus.Since bacterial activities play an important role in biooxidation pretreatment.It is known that bacterial activities were influenced by the bacterial activating method.This study used moderate thermophiles to research the impacts of different bacterial activating methods on bacteria activity.Arsenic refractory gold and FeSO₄ were used as the energy sources,and the results including the Eh and dearsenification rate of 5 different proportions of these tow kinds of energy sources were measured. The results indicated that the optimum activating condition is using pulp density 5%and 10g/L FeSO₄ as energy source.This study also researched the second activation of the bacteria by using low pulp density as energy source,and the results indicated that after second activation the dearsenification ratio goes up to 89%that 15%higher than first time activation.The optimum bioleaching conditions of the bacteria including pulp density,arsenic-containing,inoculations,pH and temperature were measured by using orthogonal design test.This article analyzed the results of orthogonal design test and indicated that pulp density 5%,air inflation 0.5L/min,inoculations 40%,pill.6,45℃was the optimum condition,and the pulp density was the most distinct factor.In order to increase the dearsenification ratio,Cyanidium caldarium strain YSK-1 was isolated from acid mine drainage from Dexing,Jiangxi province,China.YSK-1 is able to use yeast extract as carbon source and the optimum growth condition is 45℃,pH 1.5.The monoculture of YSK-1 is not able to bioleach gold ores,but the mix-culture of YSK-1, Leptospirillum ferriphilum and Acidithiobacillu caldus can obtain remarkable increase of dearsenification ratio up to 86%that is 10% higher than only mix-culture Leptospirillum ferriphilum and Acidithiobacillu caldus together when the pulp density is 8%.This result indicated that some organisms that have no bioleaching capacity themselves might play an important role in increasing bioleaching ratio, since they might have unique impacts on the bioleaching system to promote the growth of bioleaching bacteria.