Production and characterization of graphene-based nanocomposites of different natures and their applications in aqueous quinoline adsorption: A comparative study

Abstract

Quinoline (QN) is a basic nitrogenous compound normally present in the wastewater from petroleum industry, being a toxic and harmful contaminant of emerging concern. In contrast, separation methods for QN capture are essential from an economic point of view, since quinoline has a wide range of industrial applications. This work aims to study and compare the application of two graphene oxide (GO) nanocomposites - graphene oxide/agar hydrogel (GO/agar) and magnetic graphene oxide (Mag.GO) – as adsorbents for aqueous quinoline. For Mag.GO, Freundlich isotherm model was best fitted to the equilibrium data, for GO/agar all isotherm models fitted the experimental data. The maximum experimental adsorption capacities in the equilibrium were approximately 25 mg g−1 for GO/agar, and 53 mg g−1 for Mag.GO. The increase in the acetate buffer concentration did not seem to significantly affect the adsorption capacities in both composites, which might indicate the selective adsorption of QN. Adsorption-desorption tests were performed for both nanocomposites with HCl and NaOH, and quinoline was efficiently recovered with NaOH in each case, even after three adsorption-desorption cycles. Although phytotoxicity assays with quinoline solution still indicated toxic effects before and after adsorption, both adsorbents proved to be good for quinoline removal, with Mag.GO showing greater adsorption capacity.