Sorption of Palladium(II) from Nitric Acid Solutions by Silica Modified with Amino Groups

Abstract—The sorption of Pd(II), Ag(I), and Cu(II) from nitric acid solutions with silicas chemically modified with γ-(aminopropyl)trietoxysiloxane is investigated. It is assumed based on the investigation of solid phases by IR and X-ray photoelectron spectroscopy and thermogravimetry that the following processes occur during the sorption of palladium from nitric acid solutions: coordination of palladium atoms to nitrogen atoms of the functional group, interaction of palladium ions with the silica matrix, and the formation of polynuclear complexes. It is proposed to use a 5% solution of thiourea in 0.1 M HCl. It is determined that the establishment time of constant values of sorption in static conditions is as follows, min: 10 for Ag(I), 20 for Cu(II), and 30 for Pd(II). A sorbability series of ions from 2 M HNO₃ in identical conditions is as follows: A_Ag(I) > A_Pd(II) ⪢ A_Cu(II). Silver ions are not sorbed from solutions with the concentration of HNO₃ < 1 M, which will create prerequisites for the separation of ions.