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

Abstract 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.