Study On The Synergic Leaching Of Fine Lead-zinc Sulfide Ore By Moderately Thermophilic Consortia

Fine metal sulfide ore(raw ore or tailings)is difficult to sort and separate due to its small quality,large specific surface area,and high activation energy,resulting in the loss of a large amount of valuable metal and environmental pollution.At present,the main treatment of fine sulfide ores were placing in the tailings dumps,which not only occupied a large amount of place,but also the metals were easy to transformation and migration,which was great potential harm to the surrounding environment.Bioleaching has been a research spotlight in recent due to its environmental friendliness,simple operation,mild reaction,and low cost.It has been widely used in the treatment of various sulfide ores.However,less treatment of fine sulfide ores were reported.Therefore,realizing the comprehensive utilization of fine sulfide ores can effectively protect the environment,rationally use resources,and promote economic development.This study used Leptospirillum ferriphilum and Acidithiobacillus caldus to constructed a moderately thermophilic consortia to leach fine lead-zinc sulfide ore,and explored the leaching mechanism by the three phases of the leaching solution,minerals,and microorganisms during the leaching process.Furthermore,the results investigated the influence of leaching performance of L.ferriphilum+A.caldus with introduced a strain of iron/sulfur oxidizer Sulfobacillus benefaciens during the leaching process.Finally,aiming at the problem of difficult settlement of ultrafine lead-zinc sulfide raw ore,the influence of moderately thermophilic consortia on mineral settlement property was studied.Firstly,the effect and mechanism of leaching fine lead-zinc sulfide tailings by moderately thermophilic consortia were studied.The results showed that moderately thermophilic consortia could efficiently leach lead-zinc sulfide tailings,and the Zn leaching rate could reach 90%within 7 days.Introduced S.benefaciens into the moderately thermophilic consortia,the leaching environment maintained the higher redox potential,microbial activity,[Fe³⁺]and[TFe],which strengthened the leaching efficiency of the moderately thermophilic consortia.The Zn leaching rate reached 90%in 5 days and 99.55%in the 12 days.During the process,there were statistically significant and positive correlations among polysaccharides,proteins,and dissolved organic carbon(DOC)and the solution medium parameters.Secondly,the improved moderately thermophilic consortia(L.ferriphilum+A.caldus+S.benefaciens)was used to leach ultrafine lead-zinc sulfide raw ore,and compared with the leaching of fine lead-zinc sulfide tailing.The results showed that the decline rate of p H value,the rising rate of ORP value and the growth rate of microorganisms of the ultrafine lead-zinc sulfide ore were faster than tailings during the leaching process.The change of particle size and heavy metal content had an impact on the early stage of leaching,but the final leaching results were similar,which the leaching rate reached 96.44%in 8 days.The leaching rate of fine tailing changed rapidly and then slowly.The leaching rate of Zn increased rapidly to 82.46%for tailings in 2 days,and then increased slowly.While the various of Zn leaching rate of ultrafine raw ore changed slowly and then became quickly,mainly because of high Zn level.The raw ore leaching system promoted the production of polysaccharides,but inhibited the secretion of proteins,which the concentration of polysaccharides,humic acid and DOC were strongly correlated with bioleaching process.The two minerals were similar in composition but different in content,and there was no significant difference in mineral phase change during leaching process.Sphalerite,pyrite,galena and calcite in the minerals were gradually oxidized,accompanied by the surface of the mineral changed from smooth to being full of voids or grooves,meanwhile a large amount of secondary minerals(anglesite and gypsum)were formed.Finally,the influence of moderately thermophilic consortia on the settling property of ultrafine lead-zinc sulfide raw ore was studied.The results showed that the addition of microorganism could effectively improve the settling property of raw ore,the best settling effect was achieved within 12 days under the action of microorganisms,the highest settling rate increased by 60.24%within 30 min.With the passage of biological action time,microorganisms gradually attached to the surface of minerals,up to 4.9×10⁷cells/m L,which is conducive to the formation of biofilm.At the same time,microorganisms adjusted the secreted polysaccharides and proteins to change the zeta potential of minerals from negative(-10.96 m V)to positive(10.28 m V),promoted the agglomeration of minerals,increased the DV(10)and DV(50)of minerals,thereby accelerated the sedimentation rate.The use of moderately thermophilic consortia to leaching fine lead-zinc sulfide ore not only improves the utilization rate of metal resources,but also improves the settlement properties of the fine ores,which is beneficial to comprehensive reuse of sulfide ore.