Bacterial Pre-oxidation Of Refractory Gold Concentrate In An Air-lift Reactor

As the exploitation of severl large gold mine in China,China has been the biggest country in gold yield instead of South Africa.Since the rich gold mine has been incessant decreased,the refractory gold ore become the main materials for gold-produce.Bacterial pre-oxidation refractory gold ore has showed many advantages,such as low operation cost and environment friendly.Recently,it is difficult to improve the bio-oxidation ablity of bioleaching microorganisms,so we need seek some new ways to increase the biomass and optimize the growth condition of bacterials.However bio-oxidation in tank reactor is a well approach to improve the growth of bacterials,bioleaching in tank reactor barge up against the high shear rates facilitate,suspending solids and the loss of sterility.So that it is imminency to search for some techniques to solve such problems,and made the bioleaching had predominance to other hydrometallurgy ways.The airlift bio-reactor can well solve these problems,the homogeneity of the stress forces is the main advantage offered by it.It's hydrodynamic environment to developed is more suitable for cells that are susceptible to physical damage by mechanical agitation or fluid turbulence,it has the advantages of increased heat and mass transfer capacity,and a reduction in the energy consumption for mixing.However, it is a fat lot of reactor's reports about bioleaching reactors in the paper published about bioleaching of the world,it is even much less in China.Thestructural model of gas-liquid-solid threephase internal circulating fluid bed was adopted to design a laboratory scale airlift bio-reactor used for the bacterial pre-oxidation of refractory gold concentrate.A moderately thermophilic mixed culture was collected from acid mine drainage,it was adapted to have capability to oxidation of refractory gold concentrate at 45℃,pH 1.2,15g/L As(As³⁺and As⁵⁺).The adapted culture was used to pre-oxidation of refractory gold concentrate, and an orthogonal experiment was performed to investigate the effect of particle size,pulp density,aeration rate and initial pH.The results showed that -37μm particle size,5%pulp density,4L/min aeration rate and 1.2 initial pH was the optimal parameter,the arsenic leaching rate achieved to 93.5%.On the base of said airlift bio-reactor,a continuous equipment for bioleaching sulfured minerals was designed.Pre-oxidation of refractory gold concentrate by a mixed moderately thermophilic bacterias was investigated,the resoult was showed that,ounder the conditions of 8% pulp density and stay time 60h,it can deal with 0.256 kg refractory gold concentrate per day,and achieved 95.25%arsenic leaching rate.At last, the ecosystem had been researched.Employed by PCR-RFLP approach, the sequences of 16s had been analyzed,the result showed that Leptospirillum ferriphilum and Acidithiobacillus caldus are the main bioorganisms in this community,both of them are moderate thermphilic bacterium,and have a relative strong ability to resist arsenic ion. Acidithiobacillus cadus can oxidize S⁰,and that Leptospirillum ferriphilum oxidize Fe²⁺,the result of their cooperation is a well bioleaching to refractory gold concentrate.