Behavior and mechanism of graphene oxide-tris(4-aminophenyl)amine composites in adsorption of rare earth elements

Abstract

Three-dimensional (3D) graphene oxide-tris(4-aminophenyl)amine (GO-TAPAx:y) composites with different GO-to-TAPA mass ratios (x:y) were prepared by a facile one-step ultrasonic treatment. GO-TAPAx:y composites were characterized by scanning electron microscopy (SEM), nitrogen (N2) adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). Behavior and mechanism of GO-TAPAx:y composites for the adsorption of rare earth elements (REEs) were investigated. The adsorption capacities of GO-TAPA1:2 composite for Yb3+, Er3+, Nd3+, La3+ and Y3+ are 30.88, 26.52, 20.60, 11.24 and 10.52 mg/g, respectively. Effects of some important parameters including GO-to-TAPA mass ratios, contact time, reaction temperature and initial Yb3+ concentration on the adsorption were evaluated in detail. FTIR spectral and XPS analyses show that the metal complexations and ion exchanges between nitrogen/oxygen-containing species of the adsorbents and REEs are involved in the adsorption procedure besides the conventional adsorption based on specific surface area, indicating the introduction of specific molecules onto GO is beneficial to its adsorption ability. The convenient reusability and applicability of GO-TAPAx:y composites toward real samples also demonstrate their feasibility in the enrichment of REE ions.