Preparation Of Supported Zero-valent Iron Composite Nanomaterials And Study On Cr(?) Removal

Nano-zero-valent iron materials are environmentally-friendly nano-materials with high-efficiency decontamination capabilities and low prices.Because they are prone to oxidation and agglomeration problems,this article uses halloysite of different qualities,montmorillonite and halloysite in different mixing ratios.as carrier and dispersant.In the liquid system,sodium borohydride is used to reduce ferric ions to successfully prepare composite supported zero-valent iron nanoparticles.The dispersion effect and dispersion effect of the carrier material are analyzed through electron microscopy and various spectroscopy techniques.Then,through batch experiments,we explored the removal efficiency,process and mechanism of various composite zero-valent iron nanomaterials to Cr(?)in water.The main contents of this study are summarized as follows:(1)The halloysite-supported zero-valent iron nanoparticles with ?-Fe core-iron oxide shell structure were successfully prepared by the liquid-phase reduction method.The acidic liquid system activates halloysite to obtain more active sites and improves the adsorption capacity of halloysite.The zero-valent iron nanoparticles are uniformly attached to the halloysite nanotube surface through electrostatic interaction,surface tension and hydroxyl interaction,showing a good dispersion effect;the spontaneous iron oxide shell protects the internal zero-valent iron core from being oxidized and improves the antioxidant capacity of iron particles.Through comparative analysis,it is found that when the addition amount of halloysite is 1.0 g,the dispersing effect of zero-valent iron particles is better,and the iron content is relatively high.(2)After mixing montmorillonite and halloysite as a carrier,zero-valent iron nanoparticles with a core-shell structure and better dispersion effect were prepared by a liquid-phase reduction method.The zero-valent iron particles maintain a spherical shape and are uniformly attached to the surface of montmorillonite and halloysite through electrostatic interaction.The dispersion is mainly derived from the conformation between halloysite and montmorillonite and the good application of the card room structure.With the progress of the reduction reaction,the force between the surface of montmorillonite and halloysite is changed from electrostatic attraction to electrostatic repulsion,which is conducive to the development of the card room structure.The interaction between montmorillonite,halloysite and NZ? achieves dispersibility and better stability.Comparative analysis shows that when the mixing ratio of montmorillonite and halloysite is 5:5,the iron particles show the best dispersion effect,and the iron content is relatively high.(3)Various zero-valent iron nanomaterials are used for the removal of Cr(?).The result show that the removal efficiency is expressively affected by p H and solid-to-liquid ratio.And the kinetics process accord with the quasi-secondary model?the adsorption isotherm is more similar to the Langmuir equation.In the decontamination process,Cr(?)is first adsorbed to the surface of the positively charged iron particles,and then reduced to Cr(III)by heterogeneous effect;the material reuse effect is not ideal,removed by Cr(?)mainly caused by chemical action.