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Characterization of nZVI nanoparticles functionalized by EDTA and dipicolinic acid: a comparative study of metal ion removal from aqueous solutions

The simultaneous adsorption of metal ions on bare and functionalized zero-valent iron nanoparticles (nZVI) from aqueous solution was tested using inductively coupled plasma optical emission spectrometry (ICP-OES). The nanomaterials were synthetized using borohydride reduction of iron salt followed by addition of EDTA and pyridine-2, 6-dicarboxylic acid (dipicolinic acid, PDCA) in different molar ratios. Functionalized materials were characterized by FT-IR, XRD and SEM-EDS methods. The ligand attachment on the particles was confirmed by FT-IR spectroscopy. The formation of a magnetite and feroxyhyte shell on the core of functionalized nanoparticles was confirmed by the XRD study. Transformation of chain-like structures into clusters of nanospheres with smaller diameter size was observed from SEM study of EDTA-nVZI particles. The average diameter of bare nZVI particles comprised 115 nm, while EDTA functionalization resulted in an average diameter of 22 and 35 nm. The PDCA-nZVI particles obtained with the molar ratio of Fe[thin space (1/6-em)]:[thin space (1/6-em)]PDCA = 1[thin space (1/6-em)]: [thin space (1/6-em)]1 retain the chain-like structure with enlargement of the average particle diameter to 267 nm. SEM study of PDCA- nZVI particles that were produced using the ratio Fe[thin space (1/6-em)]:[thin space (1/6- em)]PDCA = 2[thin space (1/6-em)]:[thin space (1/6-em)]1 have demonstrated the unique property of elongation into ellipsoidal forms of reduced dimensions (a = 61 nm ; b = 28 nm). The simultaneous metal ion removal from aqueous solution was the most efficient in the case of bare nZVI particles (91–97%). EDTA functionalization was found to be highly selective for Cu and Cr removal (95%), while PDCA functionalization shows selective adsorption of Cu, Cr and V in an aqueous medium (93%). Iron nanoparticles functionalized with PDCA in both of the used ratios showed more efficient metal ion adsorption in the case when smaller ellipsoidal particles were formed.

iron nanoparticles ; dipicolinic acid ; EDTA ; metal ion removal ; SEM-EDS ; ICP-OES

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