Study On Performance Of Nano-feS For Molybdenum Pollution Removal From Water And Soil

Molybdenum（Mo）is an essential trace element for human beings,animals and plants,and a heavy metal widely used in industrial production.However,extensive mining of Mo mines in some areas has caused serious molybdenum pollution to the surrounding water and soil environment.Ferrous sulfide（FeS）is a kind of reductant that exists widely in nature,mainly in river and lake sediments.Studies have shown that FeS has the potential activity of reducing heavy metals and has an important influence on the migration and transformation of heavy metals in the anaerobic environment.However,the removal of Mo（VI）in water and the remediation of soil Mo（VI）pollution by nano-FeS has never been reported.The nano-FeS in this study was artificially synthesized and a series of characterization methods（TEM,XRD,XPS）revealed the surface characteristics before and after the reaction and the removal mechanism.The kinetic process and influencing factors of FeS on the removal of Mo（VI）in water body were emphatically studied,as well as the stabilizing effect of FeS on Mo（VI）in the soil and the changes of Mo（VI）morphology before and after the repair process.The results show that:1、The removal rate of Mo（VI）gradually increased with the decrease of the initial p H,which was mainly related to the surface morphology of FeS and the morphological changes of Mo（VI）at different p H.Under the influence of initial p H,Mo（VI）concentration and FeS dosage,Mo（VI）removal process by FeS were all fitted well with the pseudo first-order reaction model,and the equilibrium reached in less than 4h.Spectroscopic analyses demonstrated that Mo（VI）had been successfully reduced to Mo（IV-V）by FeS at p H 4.0.2、PO₄^3-significantly inhibited the removal of Mo（VI）by FeS.Dissolved oxygen（DO）significantly affected the removal effect of Mo（VI）by FeS,and the removal rate of Mo（VI）in air environment is reduced by 10%compared with anaerobic environment.The activity of FeS decreased with the aging time,and the removal rate of Mo（VI）by FeS at 120 days of aging decreased by 20%.The desorption experiments showed that the desorption rate of FeS after Mo（VI）reaction was lower than 1.5%,indicating that FeS had high degree stability in Mo（VI）removal and was not easy to cause secondary pollution to the environment.3、FeS can significantly reduce the amount of molybdenum leached from the soil.The concentration of Mo（VI）in aqueous phase was only 2.20 mg/L（the leaching amount was 117.60 mg/L without FeS）at the molar ratio of FeS/Mo（VI）was 50:1,which indicated that FeS increased the proportion of which indicated that FeS increased the proportion of Mo（VI）insoluble state in soil.insoluble state in soil.The addition of organic acids and inorganic anions affected the stabilizing effect of which indicated that FeS increased the proportion of Mo（VI）insoluble state in soil.in soil by FeS.Before the treatment of FeS,humic acid and salicylic acid increased the content of soluble Mo（VI）in the soil,while SO₄^2-and H₂PO₄^-promoted the transformation of soluble Mo（VI）into insoluble Mo（VI）in the soil.After the treatment of FeS,humic acid,salicylic acid and H₂PO₄^-promoted the decrease of the insoluble Mo（VI）content in the soil;while the effect of SO₄^2-on FeS stable Mo（VI）in soil was related to its concentration.When the molar ratio of SO₄^2-to Mo（VI）was0:1～0.5:1,it was the promoting effect,and when the molar ratio of SO₄^2-to Mo（VI）was 5:1～10:1,it became the inhibiting effect.This study shows that FeS can be used as an environmentally friendly material for removing Mo（VI）from water and repairing molybdenum pollution in soil.This not only contributes to a comprehensive understanding of Mo O₄^2-migration and transformation process in reductive environment,but also provides an important reference basis for the risk assessment,treatment and remediation of Mo（VI）pollution in water,soil,and sediment environment containing FeS.