3:05 PM - SM13.03.09
Late News: The Role of Additional Oxidation of Graphene Oxide on the Removal of Methylene Blue
Cecilia Zito1,Tarcísio Perfecto1,Talita Mazon2,Diogo Volanti1
São Paulo State University1,Center for Information Technology Renato Archer (CTI)2
Graphene oxide (GO) has emerged as an efficient adsorbent for environmental remediation, playing an important role in water treatment. GO-based materials have been developed for the sorption and removal of contaminants from water, including dyes,1 metallic ions,2 radionuclides,3 aromatic organic compounds,4 and so on. In particular, dyes can cause damages to humans and aquatic biota for being toxic and carcinogenic.5 The chemical composition, degree of oxidation, and size strongly affect the adsorption properties of GO. Herein, we report the repeated oxidation of GO using milder conditions of a modified Hummers’ method to obtain the modified graphene oxide (Ox-GO). The impact of the repeated oxidation was evaluated by studying the adsorption performance of the materials towards methylene blue (MB), one of the most used cationic dyes. The materials were characterized by X-ray powder diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, total X-ray scattering, and pair distribution function analysis. Our results show that the additional oxidation step does not lead to an increased content of oxygenated groups but instead, it causes a small change in the amounts of each functionality, reduces the size and introduces holes in the sheets, facilitates the exfoliation. The adsorption experiments reveal that when using an initial MB concentration of 200 mg L-1 at pH 6, Ox-GO shows a dye adsorption capacity of 695.36 mg g-1, nearly 1.32-fold higher than that of GO (527.07 mg g-1). Thus, more than 90% of MB can be removed by Ox-GO, while GO removes only 72.2%. When the pH is decreased to 2 at the same dye concentration, the difference in removal for both materials is more pronounced, where Ox-GO adsorbs 1.45 times more MB than GO, reaching an efficiency of around 79.5%. On the other hand, under alkaline conditions (pH 10), GO can adsorb almost 100% of the dye, but Ox-GO presents a catalytic behavior to converting MB into a different species, violet-colored. Therefore, the additional oxidation step of GO is an efficient method to enhance the MB adsorption performance, enabling the application in water treatment. Moreover, the material also shows catalytic properties that allow more potential applications.
This research was funded by São Paulo Research Foundation (FAPESP; grants 2018/08271-7, 2016/25267-8, 2018/00033-0, 2017/01267-1).
1 G. K. Ramesha, A. Vijaya Kumara, H. B. Muralidhara and S. Sampath, J. Colloid Interface Sci., 2011, 361, 270–277.
2 L. Chaabane, E. Beyou, A. El Ghali and M. H. V. Baouab, J. Hazard. Mater., 2020, 389, 121839.
3 A. S. Kuzenkova, A. Y. Romanchuk, A. L. Trigub, K. I. Maslakov, A. V. Egorov, L. Amidani, C. Kittrell, K. O. Kvashnina, J. M. Tour, A. V. Talyzin and S. N. Kalmykov, Carbon N. Y., 2020, 158, 291–302.
4 H. Yan, H. Wu, K. Li, Y. Wang, X. Tao, H. Yang, A. Li and R. Cheng, ACS Appl. Mater. Interfaces, 2015, 7, 6690–6697.
5 Z. Cheng, J. Liao, B. He, F. Zhang, F. Zhang, X. Huang and L. Zhou, ACS Sustain. Chem. Eng., 2015, 3, 1677–1685.