| The electrode potential of zero valent iron(ZVI)is E0(Fe2+/Fe0)=-0.44 V,which has strong reducibility and is widely used in the treatment of heavy metal wastewater.Nano zero valent iron(n ZVI)has the characteristics of small particle size,large surface area and strong surface activity,but it is easy to reunite.The nano zero valent iron can be loaded with suitable carrier to improve its dispersibility.Attapulgite has the advantages of unique rod like crystal structure,high specific surface area and low price.It is often used as the carrier of nanomaterials.In this paper,the attapulgite soil was provided by Qi Rui Mining Company in Xuyi.It was modified by sixteen alkyl three methyl ammonium bromide(CTMAB)after dispersing and purifying,and the organic modified attapulgite was prepared and used as the carrier of nano zero valent iron.The influence of ferric salt concentration,droplet acceleration of reductant,kinds of organic attapulgite and addition of ethanol on iron loading rate were investigated by orthogonal test.The modification of organic modified attapulgite,the load and dispersion of nano zero valent iron on the surface of organic attapulgite were measured by means of TEM,SEM and FTIR.The Cr(VI)in simulated wastewater was treated with nanomaterials,and the removal effect of Cr(VI)on the dosage,solution p H,reaction time and initial concentration of solution was investigated.The removal mechanism was analyzed by kinetic simulation and product analysis.The results showed that:(1)After modification of the attapulgite by CTMAB,some coarse crystal bundles and dense aggregates in the crystal are dispersed into disordered single fiber or smaller fiber bundles.CTMAB is grafted onto the surface of attapulgite by physical adsorption and does not change the original structure of the attapulgite.Under low shear rate,organic modification makes attapulgite change from non Newton fluid mode to Newton fluid mode in solution.(2)The concentration of iron salt is the main factor affecting the iron loading rate,the greater the concentration of iron salt,the higher the load rate of iron.The morphology analysis shows that the agglomeration of nano zero valent iron is serious when the carrier is not introduced,the particle size is 150-200 nm,and the dispersion of nano zero valent iron is greatly improved after the introduction of organic attapulgite carrier.The analysis shows that the nano zero valent iron load does not change the crystal structure of the original attapulgite,and the rheological analysis shows that with the increase of the shear rate,the viscosity of the three kinds of ferric soil decreases with the increase of the shear rate,and the lower the iron content on the surface of the composite under the same shear rate,the material is divided.The better the dispersivity is.(3)The removal efficiency of the Cr(VI)was much higher than that of the original soil and the organic modified soil.When the load was unloaded,the maximum removal rate was only 11.03%.After loading nanoscale iron,the removal rate of Cr(VI)was close to 100%.The higher the iron content in the composites,the higher the iron content in the composites,the more the removal rate of Cr(VI)was.Fast.Compared with the dosage,initial concentration of solution,and reaction time,the solution p H has the greatest effect on the removal efficiency of Cr(VI)in the solution.When p H increases from 5 to 11,the removal rate of Cr(VI)to the aqueous solution is reduced from 99.5% to 28.1%,and the nano iron particles are suitable for treating Cr(VI)under acidic conditions.(4)The kinetic study shows that the adsorption behavior of Cr(VI)in the solution of the attapulgite is physical adsorption,and the adsorption of Cr(VI)in the solution is chemisorption adsorption by the organic modified soil and the loaded soil.In addition,Cr(VI)was reduced to Cr(III)in the solution through the redox reaction of the nano-valent iron,and the iron on the surface of the product mainly existed in the form of Fe(III). |
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