A resin with high adsorption selectivity for Au (III): Preparation, characterization and adsorption properties

Abstract

In this paper, a novel chelating resin with high adsorption selectivity for Au (III), polystyrene-supported 3-amino-1,2-propanediol (PS-APD), was prepared simply by the reaction of chloromethylated polystyrene with 3-amino-1,2-propanediol. Its structure was characterized by infrared spectroscopy (IR), scanning electron microscope (SEM) and porous structure analysis. The adsorption capabilities of PS-APD for Pb(II), Hg(II), Cu(II), Ni(II) and Au(III) ions were investigated. The results suggested that PS-APD resin possessed much better adsorption capability for Au(III) than for other metal ions. A comparison of the kinetic models on the overall adsorption rate showed that adsorption system was best described by the pseudo second-order kinetics. The adsorption equilibrium data fitted best with the Langmuir isotherm and thermodynamic parameters including ΔG, ΔH and ΔS were calculated. The adsorption mechanism of PS-APD for Au(III) was confirmed by SEM, IR and X-ray photoelectron spectroscopy (XPS), which showed that redox reaction occurred between 3-amino-1,2-propanediol group and Au(III) ions. Adsorption selectivity experiments indicated that PS-APD resin possessed excellent adsorption property to Au(III) ions, offering potential applications in recovery of Au(III) from multi-ionic aqueous systems.

Introduction

Because of its specific physical and chemical properties, gold is widely used in many fields such as catalysts in various chemical processes, electrical and electronic industries, corrosion resistant materials and jewellery [1], [2]. Economically, gold has been historically important as currency, and remain important as investment commodity. Considering its value and scarcity, it is necessary to treat the waste aqueous solutions and try to recover gold economically. Nevertheless, the separate and recovery of gold is not actually simple, which is due to the low concentration of gold in environmental, geological and metallurgical materials and insufficient sensitivity. At present, many methods such as co-precipitation [3], ion exchange [4], [5] and solvent extraction [6] and adsorption [7], [8] have been used to separate and enrich gold. Comparatively, the adsorption of a solute on a solid support has the advantage over liquid–liquid extraction in that no mixing and settling requirements have to be fulfilled and organic phase loss through entrainment is eliminated. And the chelating adsorption seems to be the most suitable method for the recovery of precious metals in the case of low concentration due to low cost and high efficiency [9].

Resins functionalized with groups containing nitrogen or sulfur can be efficient in the adsorption of metal ions [10], [11], [12], [13], [14], [15]. Recently, we functionalized polystyrene resin with 3-amino-1,2-propanediol (APD) group, which is an important medical intermediate with very low toxicity. Originally, we designed this resin in order to selective adsorption for copper ions because the structure of APD was similar to that of glycerol, which can form stable complex compound with copper ions. However, with the proceeding of adsorption experiments, we found that the resin exhibited much better selective adsorption capability for gold ions than for copper ions, which was different from what we expected before. Therefore, the adsorption properties of polystyrene supported 3-amino-1,2-propanediol (PS-APD) resin for Au(III) including adsorption selectivity, adsorption kinetics and adsorption isotherm were investigated in detail in this paper.