Preparation Of Chitosan Modified Nano FeS And Its Application In Antimony Pollution Treatment

In recent years,due to the large-scale mining of antimony ore and the widespread use and improper discharge of industrial antimony,the concentration of antimony in groundwater has increased remarkably,which has seriously threatened the ecological environment and social security,and has attracted great attention at home and abroad.Remediation and treatment of plutonium pollution has become an important issue of global concern.The adsorption method has become the main method in the treatment of antimony pollution due to its advantages of economy and high efficiency.Since nano-FeS can release two kinds of affinity electron donors Fe（II）and S（-II）,andit has the characteristics of large specific surface area and high density of reactive sites,it has become a kind of new materials that widely applied as an in-situ treating technique in pracitical design of groundwater remediation.However,the intrinsic van der Waals force of the nano-FeS makes it extremely easy to agglomerate,resulting in a decrease in its adsorption retention capacity for pollutants.Therefore,how to modify the nano FeS to provide steric hindrance and increase the electrostatic repulsion,reducing particle aggregation has become the current research focus.In this study,nano-FeS was synthesized by chemical co-precipitation method using FeCl₂·4H₂O and Na₂S·9H₂O as raw materials.Based on this,this study proposes the use of chitosan modified nano-FeS to improve the dispersion and adsorption of nano-FeS.The effects of different chitosan dosages on the particle size,zeta potential and sedimentation performance of nano-FeS were characterized by Zeta potential,UV-VIS,SEM and FT-IR.The results showd thatthe unmodified nano-FeS was easy to settle,oxidize and agglomerate,besides it had poor stability.While the modified nano-FeS-CTS hadbetter dispersibility.The optimal dosage of chitosan was 30%,and the particle size was about 200nm.The nano-FeS-30%CTS had good migration ability in the column migration experiment.Further more,the modified nano-FeS-30%CTS was more suitable for the removal of Sb（V）in groundwater,which meets the migration requirements of nano-adsorbed materials for in-situ treatment of groundwater.Antimony exists in the environmenttpollutantion in a pentavalent form.By investigating the effect of pH,reaction time,dosage,and anion on the static adsorption reaction of two kinds of iron-sulfur compounds,nano-FeS and nano-FeS-30%CTS,the results confirmed that the modified nano-FeS-30%CTS had better absorbability than nano-FeS.This finding opens up new approaches for the application of nano-FeS in the treatment of Sb（V）.The adsorption process of Sb by nano-FeS-30%CTS and nano-FeS were both consistent with the quasi-secondary dynamic adsorption model（R²≥0.9892）,indicating that the adsorption effects of Sb on nano-FeS-30%CTS and nano-FeS depended on the chemical reactions,rather than the substance transfer in solution.The adsorption process of nano-FeS-30%CTS could be more accurately fit by the Freundlich model,and its adsorption type belongs to multi-molecular layer adsorption.The environmental tolerance of nano-FeS-30%CTS is weak,and the environmental factors such as Cl^-,NO^3-,CO₃^2-,SO₄^2-,and PO₄^3-have different removal efficiency on Sb（V）of nano-FeS-30%CTS,where PO₄^3-has the greatest impact.The antimonial tailings used in this experiment consist ofvarious crystalline substance,which mainly contain a large amount of crystalline minerals such as dolomite and calcium silicate.Its particle size distribution is not uniform,and the particle size range is-0.85mm-+0.425mm.The effects of dosage,pH value on the migration properties of nano-FeS-30%CTS composites on the tailings were investigated by dynamic column experiments.The results showed that when the aqueous solution pH was 6.5,the leaching concentrations of Sb and As were higher,1.51 mg/g and 51.43 mg/grespectively.Nano-FeS-30%CTS has strong adsorption capacity for Sb and As in tailings in column solidification experiments.With the increase of adsorbent,the adsorption capacity of nano-FeS-30%CTS to the filling medium increased,and the free diffusion weakened,eventually causing Sb and As to adsorb on the nano-FeS-30%CTS and agglomerated on the surface of the tailings.When the tailings had a particle size of 20 mesh,the migration effect of Sb and As was stronger than that of 40 mesh.The migration ability increased remarkably with the increase of the flow velocity,and the shear force increasedtoo.The migration ability of nano-FeS-30%CTS to Sb and As was obviously affected by pH environment.Both the acidic environment and the alkaline environment were not conducive to the migration of Sb,while the neutral environment was conducive to the migration of Sb.The addition of anions had a great influence on the Sb and As in the nano-FeS-30%CTS migration tailings.The greater the concentration of the added anions,the worse the migration ability.