A novel nanocomposite based silica gel/graphene oxide for the selective separation and recovery of palladium from a spent industrial catalyst

Abstract

A novel nanocomposite-based silica gel/graphene oxide (SG@GO-IIP) was prepared and applied to the recovery of palladium from a spent industrial catalyst. The nanocomposite material was characterized using Fourier-transform infrared (FT-IR), N2 adsorption-desorption, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG) techniques and a possible adsorption mechanism between Pd(II) ions and SG@GO-IIP was put forward. In addition, adsorption properties of SG@GO-IIP towards Pd(II) were investigated in detail via batch and fixed-bed experiments. The results showed that the adsorption process was well described by the pseudo-second-order kinetic and Langmuir models and that the maximum adsorption capacity achieved was 154.3 mg g−1, while adsorption equilibrium was reached within ~90 min. In the fixed-bed experiments, the effects of initial pH value, flow rate and fixed-bed height on breakthrough curves were investigated and the Thomas and Yoon-Nelson models were found to be more appropriate for describing the entire adsorption process compared to the Adams-Bohart model. The adsorption capacity of Pd(II) ions onto SG@GO-IIP reaches the maximum of 147.7 mg g−1 when pH of the solutions was 3.0, the flow rate was 0.6 mL/min and the fixed-bed height was 40 mm. The SG@GO-IIP material exhibited excellent affinity towards Pd(II) even in the presence of K(I), Na(I), Ca(II), Mg(II) and Al(III) ions, as well as possessing good regeneration and reusability properties, with its maximum adsorption capacity declining by only 8.9% after five adsorption/desorption cycles. The adsorption mechanism of Pd(II) onto SG@GO-IIP is considered to be via the formation of coordination bonds between the Pd(II) and iodine in the adsorbent. The study proposed a new method to recover palladium from a spent industrial catalyst via solid-phase extraction using SG@GO-IIP as a sorbent, sulfuric acid was chosen as the leaching liquor in the process and the technology may facilitate graphene oxide based nanocomposite materials begin to be applied by industrial applications to some extent.