Preparation Of Sulfidated Iron-based Nano-composites And Study On The Performance Of Removing Chlorinated Organic Compounds From Water

In recent years,environmental remediation technology based on nanoscale zero-valent iron(nZVI)has become an important means to solve environmental pollution problems.Because of its high reactivity,strong reducing ability,and low preparation cost,nZVI has broad application prospects in the treatment of various organic pollutants in the environment.However,nZVI has a problem of passivation during use,which brings great challenges to the practical application of nZVI.Therefore,the use of sulfidation treatment(S-nZVI)can be used to suppress the passivation of nZVI and improve its removal efficiency and electron selectivity of pollutants,thus improving the reactivity of nZVI and broadening the application in removing organic pollutants.In addition,in view of the practical problems such as agglomeration that easily occur during the preparation and application of the S-nZVI,the S-nZVI complex was formed through different synthesis methods based on the sulfidation treatment in this study to improve the dispersibility and reactivity of S-nZVI and enhance its ability to remove pollutants.This study is of great significance to improve the practical application of S-nZVI in complex natural conditions.The main research contents and research results of this study are as follows:1.Given its high activity and nontoxicity,nZVI has been intensively used to remediate the groundwater contaminated by trichloroethylene(TCE).However,the long-term stability of nZVI could be impaired by aging and natural organic matter.Herein,a montmorillonite-supported sulfurated nZVI(S-nZVI/MMT)was successfully synthesized by liquid-phase reduction method.The nZVI was intercalated between the MMT layers by the restricted effect of MMT.Nanoscale zero-valent iron with extremely small particle size exhibited robust activity and stability under environmental conditions.In this study,trichloroethylene(TCE),a typical environmental chlorinated aliphatic hydrocarbon compound,was selected as model pollutant.Experiments show that the removal efficiency of TCE by S-nZVI/MMT reached 78.7%,which was higher than that by S-nZVI and nZVI/MMT.Importantly,by studying the reactivity of S-nZVI/MMT at different application scenarios such as under different pH values,aging in water and at the presence of humic acid,it was found that S-nZVI/MMT has high stability.The presence of high concentration of humic acid(up to 50 mg/L)caused unobvious effect on the performance of S-nZVI/MMT toward TCE removal,and more than 68.1%of removal efficiency of TCE could be maintained when the particle was aged in water for 30 days.The high activity and stability of S-nZVI/MMT may be attributed to the formation of nano-sized S-nZVI clusters in the MMT interlayer,protecting the active sites from passivation of humic acid.This work may promote the application of nZVI under complex natural conditions.2.Aggregation of sulfide-modified nZVI(S-nZVI)can lower its reactivity with contaminants in water.To overcome this limitation,S-nZVI nanoparticles stabilized on biochar(S-nZVI/BC)were synthesized by the one-pot fast pyrolysis synthesis of a FeSO4-loaded lignocellulosic biomass to uniformly distribute the S-nZVI both on the exterior and interior of the biochar pores.The distribution and structure features of S-nZVI/BC were confirmed by HRTEM,XRD,and XPS.In this study,diclofenac(DCF),a typical environmental chlorinated aromatic hydrocarbon compound,was selected as model pollutant.The effectiveness of adsorption and reduction as a fast and stable process was demonstrated for the removal of DCF by removal kinetics.The removal efficiency of DCF by S-nZVI/BC-800(S-nZVI/BC obtained at the pyrolysis temperature of 800?)reached 80.1%,where the exact portion of adsorption and reduction efficiency reached 43.2%and 36.9%,respectively,within 4 h with iron loading ratio of 1 mmol/g and particle dosage of 0.5 g/L.The cycle,regeneration and long-term performance experiments of S-nZVI/BC for DCF removal demonstrate the superior reactivity and stability of S-nZVI/BC.This work provides a simple and effective method for incorporating S-nZVI into biochar supports,which has promising application potential in remediating chlorinated organic pollutants contaminated water.