| With the continuous exploitation and utilization of molybdenum resources,the utilization of various types of refractory molybdenum ores has gradually become one of the main research topics in the field of mineral processing.It has been paid more and more attention to develop an economic,rational and environmentally friendly processing method.Meanwhile,due to low production cost and environmental pollution,resources microbial processing technology has achieved a huge economic benefit in the processing of lean ore,abandoned ore and ore below cutoff grade,and it also has obvious technical superiority in the treatment of refractory ores.The refractory gold-molybdenum ore,come from Henan Luoyang,has the characteristics of fine disseminated particle size of the useful mineral,high cost of single gold extraction technology,and the associated molybdenum mineral is jordisite which is very difficult to separate.According to these,the process of separation-bioleaching of Mo-cyanide leaching of Au is put forward to study on bioleaching of the refractory gold-molybdenum in depth.The results of systematic mineralogy study on the refractory gold-molybdenum showed Mo and Au were the main recyclable elements.Jordisite was the main molybdenum-containing mineral,and a small amount of molybdite and wulfenite were also contained.Jordisite aggregate was colloid and had a symbiosis with limonite.And there was a large number of micro fine jordisite,which lead to great difficulty in separating molybdenum.It was also confirmed by the results of seperation tests.In view of the difficulty in separating gold-molybdenum ore,bioleaching of molybdenum in this ore was investigated.Firstly,A strain of bacteria was extracted from the acid mine drainage of Jiama mine area(named XZ).XZ strain,together with JL strain which was an At.f preserved in the lab,were screened and characterized systematically from the aspects of oxidation activity,energy substances,morphology,culture conditions,growth curve and 16S rDNA gene sequence analysis.Finally XZ strain was identified to be a kind of Acidithiobacillus ferrooxidans.Na2MoO4-pulp medium were used to domesticate XZ strain and JL strain,which significantly improved the tolerance of the two strains of bacteria to Mo ions.The domestication performance of JL strain was better than that of XZ strain,and JL strain could resist higher concentration of Mo ions after domesticated.Original and domesticated strains were used in the bioleaching of gold-molybdenum mixed rough concentrate.The results showed that the Mo leaching rate of domesticated strain was significantly higher than that of the original strain.Compared with XZ strain,leaching by JL strain could achieved higher Mo leaching rate.JL strain domesticated was used to bioleach molybdenite concentrate by shake flask leaching test.The leaching by bacterial and aseptic conditions were studied as well as by Fe3+;furthermore,the solution chemistry properties of the molybdenite bioleaching system under the condition of different iron ions concentration was investigated.On the basis of above,the changing regularity of iron ions concentration,pH,Eh,and the mineral surface morphology in different leaching system were analyzed.The results showed that Fe3+ could oxidize molybdenite,but the oxidation effect was worse than JL strain leaching system.Iron ions concentration were closely related to the solution pH,Eh and the generation of jarosite precipitation,which had a significant influence on the bioleaching of Mo.As for the leaching rate of Mo,4.5K system was optimal,OK system was in the second place and 9K system was minimum.The bioleaching conditions of gold-molybdenum rough concentrate were optimized by shaking flask leaching test from the aspects of culture medium,bacteria solution,inoculum quantity,pulp density,pH,leaching temperature and shaking intensity.Stirring leaching test was carried out under the optimal leaching conditions,and the stirring leaching residue was tested by cyanide leaching.The technical indicators of Mo recovery rate of 53.31%and Au recovery rate of more than 80%were obtained,which showed that Au in the ore was easy to recycle and the linchpin of comprehensive utilization was the recovery of Mo.Promotion measures to the bioleaching of molybdenite were explored by adding different kinds and concentrations of metal ions and metal sulfide mineral.The results show that,the addition of Co2+,Bi3+ and low concentration of Ag+ could not interact with the surface of molybdenite,and cannot effect the leaching of Mo obviously.However,the addition of high concentration of Ag+ could inhibit the bioleaching of Mo.Otherwise,pyrite and chalcopyrite,added to the leaching system,could contact to molybdenite and constitute the original battery,which could promote the electrochemical dissolution of molybdenite.According to the principle of chemical thermodynamics,the Eh-pH diagram in Mo-S-H2O system was drawed and the oxidation leaching process of MoS2 was analyzed.The results showed that,with the increasing of Eh,on the conditions of 1.0<pH<3.5 and 200 mV<Eh<800 mV and aerobic condition,Mo4+in the MoS2 was oxidized eventually to MoO42-and S2-was oxidized eventually to SO42-in the order of S2-?S0?S6+.The adsorption characteristics of JL strain on the surface of molybdenite was studied by taking 4.5K medium and distilled water as the dispersion medium.The results showed that,JL strain could adsorb onto the surface of molybdenite.With the existence of Fe2+,it would be preferentially oxidized,which decreased the adsorption rate of bacteria on the surface of Molybdenite.Combining with the mineral crystal structure,bioleaching test,XRD and SEM results to analyze,it could be concluded that the bioleaching of molybdenum sulfide minerals by bacteria was achieved through indirect mechanism and indirect contact mechanism. |
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