Study On In-situ Remediation Of Cr(Ⅵ) Contaminated Groundwater By Modified FeS Nanoparticles

In this study,nano-FeS(Nano-FeS),sodium carboxymethylcellulose(CMC-FeS),guar-modified FeS(GG-FeS),and rhamnolipid-modified FeS were prepared by homogeneous precipitation method.(Rh-FeS)and hydroxy aluminum pillared bentonite modified FeS(Alb-FeS).The influences of the dosages of the four modifiers on the dispersibility and sedimentation were investigated through experiments;the initial Cr(Ⅵ)concentration,initial pH value,low salinity ion intensity and high salinity ion intensity for Nano-were investigated.The effect of FeS and 4 kinds of modified FeS on the removal of Cr(Ⅵ)in water;The sedimentation performance of five kinds of ferrous sulfides(Nano-FeS,CMC-FeS,GG-FeS,Rh-FeS,Alb-FeS)was investigated through experiments.The migration performance in the medium and the colloidal filtration theory were used to calculate the deposition rate and the maximum migration distance of Nano-FeS and 4 kinds of modified FeS in the three media and different injection concentrations.The results showed that:(1)Nano-FeS was filamentous,aggregated into agglomerates and had poor stability.The main components of Nano-FeS and 4 kinds of modified FeS are FeS.The optimum dosage of CMC-FeS,GG-FeS,Rh-FeS and Alb-FeS was 0.050%,0.075%,0.075% and 0.100%,respectively.The modified FeS was with strong anti-settling properties and good stability.The FeS particle sizes were Nano-FeS>Alb-FeS>RhFeS>CMC-FeS>GG-FeS.(2)With the increase of chromium concentration,the Cr(Ⅵ)removals decreased with Nano-FeS and 4 kinds of modified FeS,and the removal capacity was NanoFeS>Alb-FeS>CMC-FeS>GG-FeS>Rh-FeS.The initial pH was the main factor affecting Cr(Ⅵ)removal.When the pH was 3,5,7,it was beneficial to the reduction of Cr(Ⅵ)by Nano-FeS and modified FeS.When the pH was 9,12,it was not conducive to the removal of Cr(Ⅵ).The impact resistance was Nano-FeS>Alb-FeS>GG-FeS>RhFeS>CMC-FeS.With the increase of ion concentration,the Cr(Ⅵ)removals decreased with Nano-FeS and modified FeS.Low salinity ions had a greater effect than high salinity ions.At high ions concentration,the impact resistance was Alb-FeS>GGFeS>Nano-FeS>CMC-FeS>Rh-FeS.(3)In the coarse,medium and fine sand,the migration properties of Nano-FeS and 4 kinds of modified FeS decreased with the decrease of the particle size of the medium and the increase of the injection concentrations.In the same medium,the migration property was Rh-FeS>CMC-FeS>GG-FeS>Alb-FeS>Nano-FeS,but the migration of CMC-FeS and GG-FeS was similar in fine sand.The increase of Fe S injection concentration would lead to more FeS deposition in the medium,but the modification rate could ignificantly reduce the deposition rate k and the deposition amount SS.The modified FeS deposition rate was Nano-FeS>Alb-FeS>GG-FeS>CMC-FeS>Rh-FeS.The maximum migration distance(Lmax)of modified CMC-FeS and Rh-FeS in medium sand was 6.4 times higher than that of Nano-FeS.