Effect Of Gangue Minerals On Bioleaching Behavior Of Marmatite And Mechanism

Microbial hydrometallurgy has become a research hotspot in the treatment of low-grade sulfide ore due to its advantages of low pollution,but the gangue mineral content in low-grade sulfide ore is high,and the effect of gangue mineral on the microbial leaching behavior of sulfide mineral is less studied.In this paper,marmatite and common gangue minerals calcite,quartz and apatite as the research object,the influence of different particle size and mass concentration of gangue minerals on the leaching process of marmatite by Acidithiobacillus ferrooxidans（A.ferrooxidans）was investigated.The main conclusions are as follows.The effect of particle size of calcite,quartz and apatite on the bioleaching process of marmatite is different.When gangue mineral concentration is 10 g/L,compared with the system without gangue mineral addition,-0.038 mm calcite promotes the bioleaching of marmatite.However,with the increase of particle size,the effect of calcite on marmatite bioleach becomes inhibition,and the marmatite bioleach is completely inhibited when the particle size reaches-0.15～+0.075 mm.The-0.038 mm quartz and-0.05～+0.038 mm quartz has no effect on the bioleaching process of marmatite.The addition of-0.075～+0.05 mm quartz and-0.15～+0.075 mm quartz completely inhibited the marmatite leaching.When the concentration of apatite was 10g/L,the bioleaching of marmatite was completely inhibited by apatite of all grades.Different gangue minerals promote or inhibit marmatite bioleaching at different critical mass concentrations.Compared with the system without gangue mineral,the critical mass concentration of calcite and quartz is 10 g/L and apatite is 3 g/L under the condition of gangue mineral grain size of-0.038 mm.When the added mass concentration is higher than the critical mass concentration,calcite,quartz and apatite can inhibit the bioleaching process of marmatite.When the added concentration is lower than the critical concentration,calcite and apatite can promote the bioleaching process of marmatite,but quartz has no effect on the bioleaching process of marmatite.Studies on the influencing mechanism show that the concentration of ions released by gangue mineral dissolution has an effect on bacterial activity in the mixed system of marmatite/calcite and marmatite/apatite.When the mass concentration of calcite is 10g/L（-0.038 mm）,the Ca²⁺of 130 mg/L in the leaching solution contributes to the growth of A.ferrooxidans bacteria and improves the bacterial concentration,thus promoting the leaching of marmatite.When the mass concentration of apatite is 3 g/L（-0.038 mm）,the mass concentration of Ca²⁺and PO₄^3-in the leaching solution is 87.21 mg/L and50.69 mg/L,respectively.The increase of bacterial concentration is conducive to marmatite leaching.In the marmatite/quartz mixed system,quartz is insoluble in the leaching solution,and the low mass concentration and small size of quartz have almost no effect on the leaching process.When gangue minerals promote marmatite bioleach,there are obvious traces of A.ferrooxidans bacteria erosion on the marmatite surface in leach residue,and jarosite precipitation is generated.When gangue minerals inhibit marmatite bioleaching,in the system containing calcite and apatite,marmatite surface in leach residue is mostly covered by sulfur layer or calcium sulfate precipitation,which hinders the interaction between A.ferrooxidans bacteria and marmatite.In the system containing quartz,the shear force generated by quartz on A.ferrooxidans bacteria increases with the increase of mass concentration and particle size,affecting bacterial activity,thus inhibiting marmatite leaching.