Study On The Repair Of Two Kinds Of Arsenic-containing Tailings By Nano-sized FeS

In the exploitation of mineral resources,arsenic-containing waste rock?tailings and smelting wastes exposed to the surface from arsenic-containing tailings.The arsenic-containing tailings deposited on the surface are under oxidation?weathering and eluviation,the arsenic in tailings is activated and diffuses into the surrounding environment in various forms,causing serious arsenic pollution of soil?water and the atmosphere.In this paper,two kinds of geo-microbiological?Acidiphilium cryputum JF-5 and Sulfate reducing bacteria?were used to synthesize Nano-sized FeS,which to clean As and U in tailing of gold mine,and explore the cleaning effect.In addition,investigated the mechanisms and products of arsenopyrite?FeAsS??realgar?As₄S₄?-containing tailing and mixture by Thiobacillus ferroxidans with and without iron slag.The infrared spectra,scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize secondary minerals.The main consequence of this study include:?1?The biologically synthetic FeS particles are black,the morphology is flake shaped and needle,and the particles have certain developed crystal panel,which is mainly composed of FeS_0.9.?2?In the process of cleaning high arsenic and high uranium samples by Nano-sized FeS,the dissolved concentration of As is higher than U.Considering the potential cleaning effect,a total of nine cycles were cleaned.The removel rate of As and U by Nano-sized FeS were 60%and 16%,respectively.The results show that the cleaning effect of As is better than U,and the increase of cleaning cycle also contributes to the improvement of cleaning effect.?3?The comparison of the samples before and after Nano-sized FeS cleaning by sequential extraction method shows that in the high arsenic sample?T002?,the removal of Nano-sized FeS is mainly residual state and bound to Fe/Al oxides state;and in the high uranium sample?T007?,the Nano-sized FeS mainly removes U which is bound to Fe/Al oxides state and easily oxidized state.?4?Acidic and alkaline minerals dissolution by Thiobacillus ferroxidans results in decreases in solution pH and increases in Eh.The lower pH and the higher Eh were beneficial to the formation of ferric arsenate.?5?In three cycles,the release concentration of arsenic in acidic mineral is higher than that of alkaline mineral.In the first and second cycles,high amounts of iron slag addition?4.0g in this experiment?resulted in a decrease in the release of arsenic,indicating that an increase in iron slag would inhibit the release of arsenic.However,in the third cycle,the more iron slag,the higher the concentration of arsenic released,which is completely opposite to the fist and second cycles.Arsenic release may be attributed to the formation of As-Fe secondary minerals and the influence of sulfate,or by passivation of the Thiobacillus ferroxidans.?6?In the process of extracting arsenic and iron by oxalate,oxalate reduction promotes the dissolution of iron oxide compound,and the As combines with iron oxide compound and is released from secondary minerals.Therefore,oxalate is effective for the extraction of As in arsenic-containing tailings.