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

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

Photodegradation of Reactive Black 5 and raw textile wastewater by heterogeneous photo-Fenton reaction using amino-Fe3O4-functionalized graphene oxide as nanocatalyst

Amino-Fe3O4-functionalized graphene oxide (AmGO) was synthesized and had its photocatalytic properties investigated in the degradation of Reactive Black 5 (RB5) dye and raw textile wastewater (RTW). Graphene oxide was synthesized via modified Hummers method and functionalized with diethylenetriamine and FeCl3 to obtain the AmGO. A 23 factorial design was carried out to optimize the best working conditions; the most statistically significant effect was the AmGO dosage, followed by the initial pH. Kinetics studies were performed and Chan & Chu model the most representative of the experimental data with R2 ≥ 0.95. Experiments of adsorption kinetics were carried out and evidenced that the adsorption of RB5 by AmGO was slower than photodegradation, in which the equilibrium state was reached after 300 min. Moreover, pseudo-second-order model showed the best fit with adsorptive capacity at equilibrium of 53.06 mg∙g−1. AmGO employment in the photodegradation of RB5 exhibited 75 % removal efficiency in less than 2h for the initial dye concentration of 100 mg∙L−1. AmGO also showed satisfactory recycling capacity, since it maintained RB5 removal up to 97 % after 6 cycles. RTW photodegradation experiments exhibited removal efficiencies of 53.25 % for apparent color, and 64.55 % for turbidity. Phytotoxicity assays using cucumber seeds showed low toxicity of the samples after photodegradation, which indicated that toxic compounds were fully mineralized