Sorption-desorption properties of graphene oxide/polyhydroquinone nanocomposite in the extraction of rare earth elements Sm (III) ions from acetic-acetate buffer systems

Abstract

The paper describes the extraction of the rare earth element Sm3+ from aqueous buffer systems by a graphene-based nanostructured composite, modified using an organic polymer – polyhydroquinone. The authors determined the important parameters of the sorption-desorption of Sm3+ ions on a new nanocomposite “graphene oxide/polyhydroquinone” during a batch test, such as: initial concentration, the sorbent weight, pH of the solution, sorption rate constants, maximum sorption capacity of the nanocomposite, percentage sorption and desorption, entropy and enthalpy of the Sm3+ extraction process. The kinetic, isothermal and thermodynamic dependences allowed to propose of the Sm3+ ions adsorption mechanisms. The kinetic data were processed by pseudo-first- and second-order, Elovich and intraparticle diffusion models, and adsorption isotherms — using the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich equations. As a result of kinetic studies, the contact time of the samarium adsorption was determined — 15 min, while the sorption capacity was 100 mg·g–1. It was found that the absorption of Sm3+ ions proceeds by a mixed diffusion mechanism and limited by the interaction “samarium ions : sorbent functional groups”. According to the Langmuir model, the maximum sorbent sorption capacity was 333.3 mg·g–1. Thus, the high efficiency of the developed graphene oxide/polyhydroquinone nanocomposite for purification of aqueous media from rare earth elements was confirmed.