A new insight on the core–shell structure of zerovalent iron nanoparticles and its application for Pb(II) sequestration

• Published in: Journal of hazardous materials Vol. 263; pp. 685 - 693
• Main Authors: Zhang, Yalei, Su, Yiming, Zhou, Xuefei, Dai, Chaomeng, Keller, Arturo A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-12-2013; Elsevier
• Subjects: Adsorption; Applied sciences; Chemical engineering; Coprecipitation; Core–shell structure; Dissolution; Exact sciences and technology; Fe(OH)3 shell; Ferric Compounds - chemistry; General treatment and storage processes; Hydrogen-Ion Concentration; Iron; Iron - chemistry; Lead (metal); Lead - analysis; Lead sequestration; Metal Nanoparticles - chemistry; Metals, Heavy; Microscopy, Electron, Transmission; Nanoscale zerovalent iron (nZVI); Nanostructure; Photoelectron Spectroscopy; Pollution; Remedies; Shells; Temperature; Thermodynamics; Wastes; Water Pollutants, Chemical - analysis; Water Purification - methods; X-Ray Diffraction; Fe(OH)3 shell; Lead sequestration; Nanoscale zerovalent iron (nZVI); Core–shell structure; High resolution; Shell structure; Nanoparticle; Waste treatment; Zerovalent metal; Ultrafine particle; Dehydration; Dissolution; Contamination; Heavy metal; Fe(OH); Depletion; Transmission electron microscopy; Core―shell structure; Adsorption; Loading; shell; Aerosols; Lead; pH; Air pollution; Fe(OH) shell
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.10.031

•The shell of nZVI is composed of 45.5% Fe(OH)3 and 54.5% FeOOH.•Fe(OH)3 shell suppresses the reduction of Pb(II).•Fe(OH)3 shell greatly promotes the co-precipitation and adsorption of Pb(II).•pH<4.5 favors Fe dissolution, while pH>4.5 promotes Pb(II) adsorption.•A reaction between Fe0 core, Fe(OH)3 and Pb(II) is proposed.
Nanoscale zerovalent iron (nZVI) has shown a high efficacy for removing heavy metals from liquid solution. However, its removal capacity has not been fully explored due to its common shell composition (FeOOH). In this study, a much higher removal capacity of Pb(II) is observed (1667mgPb(II)/gFe), which is over 100% higher than the highest removal capacity of nZVI reported before. High-resolution X-ray photoelectron spectroscopy (HR-XPS) reveals that through restricting the dehydration process of Fe(OH)3, nZVI can acquire a unique shell, which is composed of 45.5% Fe(OH)3 and 54.5% FeOOH. The presence of Fe(OH)3 suppresses the reduction of Pb(II), but greatly promotes the co-precipitation and adsorption of Pb(II). Combining the ratio of Fe-released to Pb-immobilized and the result of HR-XPS, a reaction between Fe0 core, Fe(OH)3, and Pb(II) is proposed. The Fe released from the Fe0 core leads to the core depletion, observed by transmission electron microscopy (TEM) under high Pb(II) loading. While temperature has little influence on the removal capacity, pH affects the removal capacity greatly. pH<4.5 favors Fe dissolution, while pH>4.5 promotes Pb(II) adsorption. Given the high Pb removal capacity via the Fe(OH)3 shell, nZVI can be used to remedy Pb(II) contamination.