Comparative approach towards the adsorption of Reactive Black 5 and methylene blue by n-layer graphene oxide and its amino-functionalized derivative

• Published in: Adsorption : journal of the International Adsorption Society 2020-02, Vol.26 (2), p.283-301
• Main Authors: Fraga, Tiago José Marques, de Souza, Ziani Santana Bandeira, Marques Fraga, Daysianne Mikaella dos Santos, Carvalho, Marilda Nascimento, de Luna Freire, Eleonora Maria Pereira, Ghislandi, Marcos Gomes, da Motta Sobrinho, Maurício Alves
• Format: Article
• Language: English
• Subjects: Adsorption; Atomic force microscopy; Cations; Chemical oxygen demand; Chemisorption; Chemistry; Chemistry and Materials Science; CI Reactive Black 5; Dyes; Engineering Thermodynamics; Graphene; Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Infrared analysis; Methylene blue; Organic chemistry; Oxidation; Reaction kinetics; Surfaces and Interfaces; Thermogravimetric analysis; Thin Films
• ISSN: 0929-5607; 1572-8757
• DOI: 10.1007/s10450-019-00156-9

N-layer graphene oxide (nGO) was synthetized from graphite oxidation via the modified Hummers method and then functionalized with diethylenetriamine to obtain the novel n-layer amino-functionalized graphene oxide [nGO-(NH)R]. Scanning electron and atomic force microscopies, thermogravimetric analysis, Raman and infrared spectroscopies and X-ray diffraction were employed to characterize nGO and nGO-(NH)R. This nanosorbent was then evaluated through the sorption of anionic Reactive Black 5 (RB5) and cationic methylene blue (MB). pH effect analysis showed that adsorption of anionic RB5 were not influenced by pH changes; on the other hand, cationic MB adsorption was higher at pH 12.0. Langmuir isotherm best fitted the adsorption of both dyes onto nGO-(NH)R and showed maximum monolayer adsorption capacity of 3036.43 and 335.86 mg g −1 for MB and RB5, respectively. Adsorption kinetics indicated that the system reached the equilibrium state within 5 min for MB, and after 90 min for RB5, with adsorption capacity at equilibrium (q e ) of 977.06 and 177.85 mg g −1 and kinetic constant (k S ) of 3.17 × 10 −2 and 2.40 × 10 −3 g mg −1  min −1 , for MB and RB5 respectively. Additionally, pseudo-second-order model was better fitted to the experimental data for the adsorption of both dyes in nGO and nGO-(NH)R. Thermodynamic parameters exhibited the following values: ΔHº, − 150.01 kJ mol −1 , 92.83 kJ mol −1 and ΔGº (at 298 K), − 37.94 and − 22.86 kJ mol −1 , for MB and RB5 removal onto nGO-(NH)R respectively, which evidenced the spontaneous adsorption of both dyes and chemisorption behavior of RB5. Recycling experiments showed that the nGO-(NH)R maintained the MB and RB5 removal rate above 95% and 58%, respectively, after ten cycles. Experiments with raw textile effluent showed a decrease of 55% in chemical oxygen demand (in mg O 2  L −1 ) and 90% of its concentration after adsorption by nGO-(NH)R.