Lin Tai-Lin, Lien Hsing-Lung
Department of Civil and Environmental Engineering, National University of Kaohsiung, Kaohsiung City 811, Taiwan.
Int J Mol Sci. 2013 May 8;14(5):9834-47. doi: 10.3390/ijms14059834.
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.
研究了用硫脲改性的磁性磁铁矿纳米颗粒（MNP-Tu）在酸性水溶液中对贵金属的吸附。合成并表征了MNP-Tu，并将其作为一种可重复使用的吸附剂用于回收贵金属。吸附动力学符合准二级方程，而吸附等温线符合朗缪尔方程和弗伦德里希方程。在pH值为2和25°C时，通过朗缪尔模型测定的MNP-Tu对Pt(IV)、Au(III)和Pd(II)的最大吸附容量分别为43.34、118.46和111.58 mg/g。即使在存在高浓度竞争离子（Cu(II)）的情况下，MNP-Tu对贵金属仍具有高吸附选择性。此外，MNP-Tu可以用含有0.7 M硫脲和2% HCl的水溶液再生，其中贵金属可以以浓缩形式回收。发现MNP-Tu经过七个连续的吸附-解吸循环后仍保留了对贵金属的原始吸附容量。观察到在MNP-Tu表面发生还原吸附，导致形成元素金和钯。
