Selectivity of modified pomegranate peel for gold, platinum, and palladium: Adsorption behavior, mechanism, and recovery

Abstract

Recovery of precious metals from smelting, refining, and other industrial process effluents has received increasing attention from both industry and the scientific community. A novel bioadsorbent capable of selectively adsorbing gold, platinum, and palladium was synthesized in this study by simple modification of crushed pomegranate peel (PP). The mechanisms of adsorption and reduction of the adsorbents were mainly analyzed and characterized by Fourier transform infrared spectrometer (FTIR), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The determination and modeling of the adsorption isotherms and kinetics data were also undertaken in this study. The maximum adsorption capacity for Au(III), Pt(IV), and Pd(II) in 0.1 M HCl media at room temperature was 34 mg/g, 1.16 mg/g, and 1.05 mg/g, respectively. More than 95.4 % gold ions, 85.2 % platinum ions, and 97.5 % palladium ions would be reduced to be their elemental metal after selective adsorption by the rich hydroxyl groups in the polyphenolic aromatics. In addition, the effect of pH and coexisting base metal impurity ions on the adsorption efficiency of Au(III), Pt(IV), and Pd(II) were evaluated. The Langmuir isotherm model was found to be consistent with the adsorption isotherm, and the pseudo-second-order model was more appropriate to describe the adsorption. The effectiveness of practical recovery of Au(III), Pt(IV), and Pd(II) from real industrial effluent was examined using PP gel. The present study provided a quite promising novel material, pomegranate peel adsorbent, which exhibited great potential for the recovery of precious metals from various industrial effluents.