title: Effective and selective recovery of precious metals by thiourea modified magnetic nanoparticles.
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.
authors.affiliation: Department of Civil and Environmental Engineering, National University of Kaohsiung, Kaohsiung City 811, Taiwan. lien.sam@nuk.edu.tw.
authors.forename: Tai-Lin
authors.initials: TL
authors.lastname: Lin
authors.forename: Hsing-Lung
authors.initials: HL
authors.lastname: Lien
mesh_terms: D000327:Adsorption; D006046:Gold / Q000302:isolation & purification*; D055772:Green Chemistry Technology; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010165:Palladium / Q000302:isolation & purification*; D010984:Platinum / Q000302:isolation & purification*; D013890:Thiourea / Q000737:chemistry*
chemical_list: D058185:Magnetite Nanoparticles; D010984:Platinum; D010165:Palladium; D006046:Gold; D013890:Thiourea