Controllable Preparation Of Zero-valent Iron Nanoparticles For Experimental Study On Removal Of Cr(?) Contaminants From Water

Zero-valent iron nanoparticles have many novel physicochemical properties different from the bulk counterparts,and the application of its preparation under specific conditions is beneficial to theory research and practical application in this field.This work attempted to synthesized zero-valent iron nanoparticles controllably in borohydride reduction systems with montmorillonite from different location and montmorillonite modified by different protonation extent of polyethyleneimine?PEI?as hosts.Batch tests were carried out to investigate the adsorption of Cr???by zero-valent iron nanoparticles loaded upon montmorillonite from Sanding which has minimum size.These results would be important for use of zero-valent iron nanoparticles in remediation of Cr???-contaminated water.The main research results of this paper are as follows:?1?The cation exchange capacity of montmorillonite and N₂-BET specific surface area have significant influences on the size of zero-valent iron nanoparticles loaded upon montmorillonite.The larger the cation exchange capacity and the N₂-BET specific surface area were,the easier obtaining the smaller size of zero-valent iron nanoparticles were.Based on the montmorillonite from Sanding with carriers presenting the largest cation exchange capacity and large specific surface area,the minimum size?The average particle size is about 55.3 nm,which is much smaller than zero-valent iron particle size with 71.5 nm by the uniform nucleation.?near-spherical nanoscale zero-valent particles were prepared,wherein the shell?iron oxide?preserved the core?metallic iron?from complete oxidation in air atmosphere.?2?The protonation extent of polyethyleneimine had vital but complex influence on the size,dispersion,morphology,and even phase identity of the resultant iron particles.At the 90%protonation extent,optimized iron particles were obtained as nearly spherical smallest-sized core-shell entities?63 nm mean diameter?well dispersed on the external clay mineral surface,wherein the shell?amorphous iron oxide?preserved the core?polycrystalline metallic iron?from complete oxidation in essential.This regulation largely depended upon three factors:?a?the polymer interfacial conformation at clay mineral surface and?b?the relevant card-house-type pore feature as well as?c?the complexation of the unprotonated polymer amino groups with the precursor ferric ions.The formation of the clay mineral card-house-type pore structure?in dry state?would be caused by washing and drying the electrostatic-steric stabilized polymer/clay mineral composite particles from the final dispersion under suitable conditions?with ethanol and acetone diluents and by vacuum-drying at 25oC?.?3?At the optimized solution p H of 1.0,the Cr???uptake was mainly governed by the reduction of Cr???to Cr?III?at the interface of metallic iron,which could be accessed by Cr???owing to the dissolved oxide shell in acdic medium.The kinetics of the adsorption followed the pseudo-second-order model,the adsorption data fitted well with the Langmuir equation,and the adsorption was spontaneous and exothermic in nature.