Study On The Effect Of Acidithiobacillus Ferrooxidans And Its Extracellular Polymeric Substances On The Leaching Of Antimony Pollutants From Antimony Containing Tailings

The interfacial interaction between bacteria and minerals involves processes such as electrochemistry,biochemistry and surface chemistry.Therefore,the formation of Extracellular Polymeric Substances（EPS）plays an important role in the interfacial interaction of bacteria-mineral surfaces.The"contact leaching mechanism"is now generally accepted.At present,the research on the contact leaching mechanism of leaching microorganisms basically focuses on pyrite,and the research content is only limited to the initial adsorption stage of leaching bacteria and minerals,while the specific details of leaching bacteria EPS in the process of mineral leaching are limited.The role of antimony tailings is still uncertain,and the research on antimony tailings is still in the optimization stage of the leaching process,but the research on the role and impact of EPS in the leaching of antimony tailings is rarely reported in the literature.Based on the existing research results of leaching antimony tailings with Acidithiobacillus ferrooxidans（At.f）,this paper first stabilized the bacterial leaching ability through domestication experiments;and Sb（V）toxicity and determination of the added concentration of EPS for extraction;different treatment groups were used to leaching tailings,and the mechanism of At.f in the leaching process of antimony tailings was further studied by means of SEM and XRD.For EPS produced by At.f,the changes of functional groups,humic substances and protein substances in EPS before and after leaching were studied.Finally,the effect of EPS was verified by simulation experiments,and the following conclusions were drawn:（1）Through the continuous acclimation experiment,the inhibition zone experiment and the effect of simulated extracellular polymer on the leaching of tailings,the effect of the continuous acclimation experiment on the leaching ability of bacteria,the toxicity of Sb（III）and Sb（V）,and the simulated cell leaching ability were explored.The effect of exopolymer on tailings leaching,the results show that the continuous domestication experiment can effectively promote At.f to adapt to the highly toxic leaching solution,so that the leaching results are more stable;at the same time,the logarithmic phase of At.f after domestication is advanced.The Oxford cup inhibition zone test proved that Sb（III）was more toxic than Sb（V）,and 10 mg/L Sb（III）was more toxic than 5 mg/L Sb（III）.The simulated extracellular polymer has a certain promotion effect on the leaching of Sb in tailings,and the addition of 1 g/L simulated extracellular polymer has the best effect.（2）The shake flask leaching methods of acid leaching group,Fe³⁺experimental group,At.f group and At.f+Fe³⁺group were used to compare and analyze the leaching of Sb in tailings under various leaching methods.The order of leaching capacity was:At.f group>At.f+Fe³⁺experimental mixed group>Fe³⁺experimental group>acid leaching group,the bacteria mainly leached Sb in tailings by direct action.Combined with SEM and XRD,the dissolution process of Sb in tailings,the mechanism of action of At.f,and the morphology of tri-pentavalent Sb in the leaching solution were analyzed.The results showed that in the presence of bacteria,part of Sb（V）in the solution would be gradually reduced to Sb（III）.During the leaching process,At.f will adsorb on the mineral surface and produce EPS,and EPS will adsorb Sb.（3）The changes of physical and chemical properties of EPS before and after leaching were investigated from the aspects of composition,EEM,molecular weight,UV-Vis and FTIR.The results showed that the functional groups of EPS did not change before and after leaching,but the content changed accordingly.After leaching,the-OH content ratio in EPS decreased while the-C=O content ratio increased,indicating that EPS may reduce the adsorbed Sb（V）to Sb（III）during the leaching process.The EPS in each period after leaching were distributed in the whole five regions,and most EPS appeared in region IV（tryptophan-containing protein-like substances）and region V（humin-like substances）.At the same time,through the simulated addition experiment,it is proved that EPS has the ability to reduce Sb（V）.Although the reduction efficiency of EPS to Sb（V）is low,the mobility and universality of EPS make it suitable for the transformation of Sb in natural environment.significance cannot be ignored.