Preparation Of Nano As₂S₃ From The Arsenic Residue Using A Two-step Reaction Of Bioleaching And Bioreduction

The development of high and new technology of industrial waste harmless and resourceful has become the focus of research at home and abroad,with the shortage of resources,Arsenic-containing waste is mainly derived from the extraction of arsenic-containing metal ores,arsenic-containing waste gas and wastewater which formed by the"solid arsenic"process.After entering the environment,it will cause serious pollution of the atmosphere,water and soil,and endanger human health.At the same time,arsenic waste residue can be used as the second resource for recycling,and various kinds of arsenic products can be extracted from it.The traditional recovery technology of arsenic containing waste including thermal treatment,wet extraction processes by using chelating agents Unfortunately,these techniques suffer from the main disadvantage of high-energy requirement,as well as the liability of hazardous chemical usage during the treatment.In this study,the bioleaching of arsenic residue for detoxifying As has also been considered more economical and environmentally friendly,as compared to traditional metals extraction methods with high energy cost and increase in pollution load of environment.The optimum conditions for the bioleaching process were explored.At the same time,the biosynthesis was used to synthesize arsenic sulfide of nanomaterials,and the synthesis conditions were studied.The studies showed that the system of Acidithiobacillus thiooxidans is superior to the mixed culture with Acidithiobacillus thiooxidans,Leptospirillum ferriphilum and Acidithiobacillus ferrooxidans in the dissolution efficiency of arsenic.Reduction mechanism and acid-soluble oxidation mechanism are coexist through the whole bioleaching progress.The iron content in arsenic waste residue is 15.93%,As achieved poor efficiency with high concentration of iron ion,confirming the formation of FeAsO₄,Ca₂As₂O₇,Mn₂As₂O₇ caused lower extraction through the XRD.The dissolution rate of arsenic was optimized by changing the solid-liquid ratio and initial pH value.The optimum solid-liquid ratio was 4%and at pH 1.0.Under the optimum leaching conditions,the leaching rate of arsenic is up to 37%.The acid soluble arsenic is completely dissolved,and arsenic in oxide bound arsenic is dissolved 80%.The remaining form of arsenic in the form of residual state,to achieve the harmless arsenic residue.Study on preparation of nanometer material arsenic sulfide by simulated biological leaching liquid.At the concentration of 0.8 mol·L^-11 lactic acid,the synthesized arsenic sulfide nanomaterials are uniformly distributed and show smooth As₂S₃ nanospheres,and the particle size is mainly around 5nm.Under the optimum concentration of lactic acid,nano material As₂S₃ was successfully prepared by bioleaching.The peaks appeared in the analysis of XRD,the main reason is that the biological filtrate contains a large amount of Fe,Mn,Ca and other elements,making the synthesis of nanomaterials containing As₂S₃mixture.