Leaching Of Sulfide With Biological-chemical Process By Acidithiobacillus Ferrooxidans

With the development of technology and because of the long leaching period and low leaching rate,the traditional bioleaching process needs to be reformed.Based on the cooperative leaching mechanism,a new bioleaching process comprising biooxidation and chemical leaching is proposed.The principle of this whole process can be summarized as follows:firstly the leaching solution in the chemical reactor would react with sulfide to produce Fe²⁺,then the Fe²⁺passed to bioreactor would be biologically oxidized to ferric ions which subsequently be recycled to chemical reactor by a HL-2S peristaltic pump reacting with the sulphide minerals again.The process features the continuous production of ferric and the respective improvement of chemical and biological process.The ferric leaching of pentlandite was favored by the rise of temperature,the increase of Fe³⁺which is in constant with the indirect mechanism,and the partial replacement of SO₄^2-with Cl^-.In view of the cost,T=50℃,[Fe³⁺]=9 g/L,Cl^-=3.8 g/L were selected as the optimal parameters for the biological-chemical leaching process.Because immobilized At.f could increase the number of microorganism,accelerate the formation rate of Fe³⁺.But immobilized cell would lead to the formation of a lot of jarosite,which decrease the quantity of Fe³⁺.Thus the leaching rate of Ni by immobilized At.f is lower than the leaching rate of Ni by free At.f.In order to utilize the high Fe²⁺oxidation rate by immobilized At.f,the decrease of pH value and the concentration of(NH₄)₂ SO₄ was tried to decline the formation rate of jarosite.And the results showed that the formation rate of jarosite by immobilized At.f is still higher than the free At.f even though the formation rat of jarosite by immobilized At.f is lowed at certain extent.When the chemical reactor was not stirred,with a pulp density of 5%and temperature of 50℃in chemical reactor,a leaching rate of 60%was achieved at 9 days by this biological-chemical process.So in order to further enhance the leaching efficiency,stirring the leaching rate by air was also tried.Under the same conditions,the leaching rate of this alternative was 83.8%at 5 days.However,the leaching rate of chalcopyrite by the biological-chemical process was not satisfactory,which can be attributed to the formation of an inert film which is different from sulfur film which is produced for the leaching of pentlandite.This inert film was not stable until with a temperature above 80℃.