Rapid and efficient recovery of silver with nanoscale zerovalent iron supported on high performance activated carbon derived from straw biomass

Abstract

High performance activated carbon (HPAC) supported nanoscale zerovalent iron (nZVI) was prepared and used for recovery of silver. This composite material was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The removal amount of Ag⁺ increased with pH values and temperature. The removal process achieved equilibrium within 40 min and the maximum removal capacity was 986.5 mg/g at 298 K. The composite material showed fast adsorption rate and high adsorption capacity because the presence of high surface area activated carbon could effectively inhibit aggregation of nanoscale zerovalent iron, thus enhancing its reactivity. The Ag⁺ removal followed pseudo-second-order kinetic model and Langmuir isotherm model. XPS and XRD characterizations were performed to elucidate removal mechanism. It could be concluded that both coordination adsorption and reductive precipitation contributed to removal of Ag⁺ on the nZVI/HPAC.

Keywords: Activated carbon; Coordination adsorption; Nanoscale zerovalent iron (nZVI); Reductive precipitation; Straw biomass.