Effective and selective recovery of precious metals by thiourea modified magnetic nanoparticles

Int J Mol Sci. 2013 May 8;14(5):9834-47. doi: 10.3390/ijms14059834.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Gold / isolation & purification*
  • Green Chemistry Technology
  • Magnetite Nanoparticles / chemistry*
  • Palladium / isolation & purification*
  • Platinum / isolation & purification*
  • Thiourea / chemistry*

Substances

  • Magnetite Nanoparticles
  • Platinum
  • Palladium
  • Gold
  • Thiourea