Study On The Bioleaching And Mechanism Of Metals From Nickel-molybdenum Ore Tailings With Acidthiobacillus Ferrooxidans

Nickel-molybdenum ore tailings cannot be ignored for environmental problems and as a special resource,to study on the bioleaching and mechanism of metals from Nickel-molybdenum Ore tailings with microorganism.This paper is using Acidthiobacillus ferrooxidans?At.f strain?,which isolated from Nickel-molybdenum mine,Stone town,Zunyi,Guizhou,and bioleching the mine tailings with this strain.Through the study of metal's effect on At.f bacteria oxidation ability,experiments of different influencing factors on bioleaching were investigated in shake flask,and leaching tailings experiment and microbial leaching mechanism were also explored,lately reaction volume and self-made microbial reactor of 4 L leaching were tested.A series of experimental results are analyzed and summarized:?1?In order to determine the influence of metal ions for oxidation activity of At.f strain,the oxidation activity of the domestication At.f bacteria were measured under different concentrations of Ni²⁺,Cu²⁺,Zn²⁺ and this three metal ions coexisting effects on the strain oxidation activity.The result showed that At.f bacteria when T=32±0.5 ?,r=150±5 r/min,the initial p H was 1.8,the At.f bacterial tolerance concentration of Ni²⁺ and Zn²⁺ was above 20 g/L,while the strain was more sensitive to Cu²⁺,At.f bacteria oxidation activity had severely inhibited in 80 h when the Cu²⁺concentration was 10 g/L;when Ni²⁺,Cu²⁺,Zn²⁺ the three kinds of metal ion concentration was2.5 g/L correspondingly,which seriously inhibited the strain growth activity within 48 h,when metal ions concentration was 5 g/L correspondingly,and the oxidation of Fe²⁺ was only 4.61% in80 h,indicating that Ni²⁺,Cu²⁺,Zn²⁺ coexisting influence on bacteria oxidation activity was greater than the effect of single metal ion.The results of the study were important reference value for the treatment of complex multi metal minerals with At.f bacteria.?2?The influence of single factor of different Nickel-molybdenum ore tailings mass concentrations,and initial p H and initial Fe²⁺ mass concentrations of At.f strain leaching valuable metals of nickel molybdenum tailings was carried out in shake flasks.The result showed: Lowpulp density was helpful for bioleaching,when Nickel-molybdenum tailings concentration was 10g/L,with a higher rate of metal tailings leaching,Ni:50.97%?Mo:4.35%?Cu:77.36%?Zn:59.81%?As:23.31%?Cr:18.73%.While p H ranged from 1.4 to 2.6,the bioleaching rate was small difference,and the leaching rate of Ni?Mo?Zn?Cu?Cr was about 50%?5%?60%?78%and 18%.The effect of p H on the bioleaching of tailings was small,because the stain gradually adapted to the high or low pH environment in the 16 d leaching test.In the leaching system,adding Fe²⁺ could promote the leaching of nickel molybdenum metal tailings.In general,Fe²⁺concentration was 9 12 g/L,which was beneficial to the bioleaching of tailings.In addition,when added the concentration of Fe³⁺ was increased to 1 g/L,which could enhance the bioleaching.?3?There was a great difference in the leaching rate of metals under different leaching conditions.As in tailings increased with the leaching of ore,and the leaching rate of metals in 2days was fast when the Fe³⁺ was immersed,and then not changed.The leaching residue was characterized by SEM,indicating that At.f bacterium was attached in the tailings during bioleaching,and the surface of bioleaching residue was clear water chestnut,but on the surface of Fe³⁺ leaching residue had precipitated substance was formed,which was confirmed that jarosite by XRD.Compared to the control and bacterial leaching residue in XRD showed that At.f bacteria under the action of mineral tailings dissolved Nickel-molybdenum.At.f bacteria to indirect mechanisms of nickel molybdenum tailings leaching of Mo and Cu,and As in direct oxidation of the strain from the tailings dissolved out,but the leaching of Cr was no obvious effect on Ni and Zn,mainly in the early indirect mode of action in late stage leaching,direct oxidation of At.f bacteria later.The strain will strengthen the electrochemical reaction of bacteria leaching tailings Mo.In the process of leaching,At.f bacteria continuously oxidized Fe²⁺ in order to ensure the system has a high redox potential,which enhanced the oxidation properties of the leaching system,and constantly produce Fe³⁺,and strengthen the leaching of tailings.?4?The self-made microbial reactor leaching of Nickel-molybdenum tailings showed that the leaching rate of Cu and Zn were 61.90% and 58.33% at 32 ?,while Ni,As,Cr and Cd leaching rate and test temperature?27 to 37 ??were positively correlated.The tailings particle size is smaller,more conducive to the bioleaching of tailings in the reactor?except Cr?.The metal leaching rate decreased with the increase of the concentration of tailings in the reactor,when thetailings concentration was 10 g/L and 20 g/L,the rate of metals rate of difference was small.Compared to the tailings concentration increased 20 g/L and 50 g/L,Ni,Cu,Zn leaching rate was2.97 times,2.92 times,3.49 times,respectively.