Preparation And Adsorption Degradation Performance Of Nano Zero-valent Iron Composites

Nano zero-valent iron refers to zero-valent iron nanoparticles with a particle size of 1-100 nm.It has the advantages of large specific surface area,strong reducibility,low price and high reactivity,so it is widely used to treat various pollutions in water.However,it is easy to agglomerate and oxidize,which makes it to be greatly limited in practical applications.Based on the structural characteristics of natural clay mineral attapulgite and conductive polymer,a method based on surface modification of nano zero-iron was proposed.Nano zero-valent iron/attapulgite(nZVI/APT)and nano zero-valent iron/attapulgite/polyaniline(nZVI/APT/PANI)composites were prepared by introducing rod-like structure of attapulgite with high specific surface area and conductive polymer polyaniline containing functional groups as carriers into the modification of nZVI.Based on the characteristics of nano zero-valent iron can slow release Fe2+ in aqueous solution.Combining the reduction of nano-zero-valent iron with the Fenton oxidation of persulfate,the adsorption and degradation properties of organic pollutants and heavy metal ions were investigated.The main research contents are as follows:(1)The attapulgite supported nano zero-valent iron(nZVI/APT)composite was prepared by chemical liquid phase reduction using attapulgite as the carrier.The decolorization effect and degradation mechanism of the composite materials on crystal violet(CV)and malachite green(MG)were studied respectively.The effects of different materials,pH and dosage on the removal performance of the two dyes were investigated.The degradation process of the two types of dyes was analyzed by kinetic model and thermodynamic model.The results show that the nZVI/APT composite has high removal performance for crystal violet and malachite green,and the removal rates are 99.5%and 97.3%,respectively.The adsorption process of crystal violet and malachite green conforms to the pseudo-second order kinetic model.The thermodynamics accords with the Langmuir isotherm regression equation and the adsorption process is spontaneous and endothermic.The theoretical maximum adsorption capacity can reach 370.4mg/g and 333.3mg/g,respectively.After 7 times of composite regeneration,the removal rates of CV and MG were still as high as 70.8%and 68%.(2)The supported nano zero-valent iron was synthesized by chemical liquid phase reduction using attapulgite as the carrier.The removal performance of APT supported nZVI on Cr(?)and phenol in the presence of persulfate(Ps)was studied.The effects of different materials,different mass ratios of APT and nZVI,pH,Persulfate concentration and Cr(?)to phenol concentration ratios on the removal of Cr(?)and phenol removal were investigated.The removal mechanism was discussed by using different free radical scavengers.The results show that nZVI/APT can effectively remove Cr(?)and phenol in the presence of persulfate.The removal rate of Cr(?)can reached 99.20%,and the removal rate of phenol was 82.2%.Among them,APT as a carrier can effectively reduce the agglomeration of nZVI and increase its reactivity.The removal of Cr(?)is mainly reduced by nZVI to low-valent Cr(?).The removal of phenol is due to the oxidative degradation of sulfate radical anions generated by the reaction of persulfate and Fe2+.(3)The attapulgite/polyaniline composite supported nano zero-valent iron(nZVI/APT/PANI)composites were prepared by one-step oxidation using Fe3+ as oxidant and iron source,and aniline as raw material.In the presence of persulfate,the removal performance and mechanism of nZVI/APT/PANI composite on Cr(?)and orange yellow G6(OG6)was studied.The main factors affecting the removal performance of Cr(?)and OG6 were investigated(different composite materials,pH value,Ps concentration,etc.).The results showed that the removal efficiency of Cr(VI)and OG6 by nZVI/APT/PANI composite could reach 99.70%and 99.4%when the mixture solution pH=3,the dosage of the composite was lg/L,the oxidant potassium persulfate concentration was 2mM,the initial concentration of Cr(?)and OG6 was 30mg/L,respectively.The nZVI/APT/PANI and Ps composite system combines the reduction of nZVI with the Fenton oxidation of sulfate radical,and can be used for organic dye OG6 and heavy metal Cr(?)achieve high efficiency simultaneous removal.