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Int. J. Mol. Sci. 2013, 14(5), 9834-9847; doi:10.3390/ijms14059834
Article

Effective and Selective Recovery of Precious Metals by Thiourea Modified Magnetic Nanoparticles

 and
*
Department of Civil and Environmental Engineering, National University of Kaohsiung, Kaohsiung City 811, Taiwan
* Author to whom correspondence should be addressed.
Received: 1 April 2013 / Revised: 26 April 2013 / Accepted: 3 May 2013 / Published: 8 May 2013
(This article belongs to the Special Issue Magnetic Nanoparticles 2013)
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Abstract

Adsorption of precious metals in acidic aqueous solutions using thiourea modified magnetic magnetite nanoparticle (MNP-Tu) was examined. The MNP-Tu was synthesized, characterized and examined as a reusable adsorbent for the recovery of precious metals. The adsorption kinetics were well fitted with pseudo second-order equation while the adsorption isotherms were fitted with both Langmuir and Freundlich equations. The maximum adsorption capacity of precious metals for MNP-Tu determined by Langmuir model was 43.34, 118.46 and 111.58 mg/g for Pt(IV), Au(III) and Pd(II), respectively at pH 2 and 25 °C. MNP-Tu has high adsorption selectivity towards precious metals even in the presence of competing ions (Cu(II)) at high concentrations. In addition, the MNP-Tu can be regenerated using an aqueous solution containing 0.7 M thiourea and 2% HCl where precious metals can be recovered in a concentrated form. It was found that the MNP-Tu undergoing seven consecutive adsorption-desorption cycles still retained the original adsorption capacity of precious metals. A reductive adsorption resulting in the formation of elemental gold and palladium at the surface of MNP-Tu was observed.
Keywords: magnetic nanoparticle; thiourea; precious metals; reuse; recycle; green material; adsorption; nanotechnology magnetic nanoparticle; thiourea; precious metals; reuse; recycle; green material; adsorption; nanotechnology
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Lin, T.-L.; Lien, H.-L. Effective and Selective Recovery of Precious Metals by Thiourea Modified Magnetic Nanoparticles. Int. J. Mol. Sci. 2013, 14, 9834-9847.

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