Effects of the Coagulation Bath and Reduction Process on SO2 Adsorption Capacity of Graphene Oxide Fiber
Sulfur dioxide (SO2) is a very toxic air pollutant gas and it causes the greenhouse effect, photochemical smog, and acid rain, which threaten human health severely. Thus, the capture of SO2 gas is very important for the environment. Graphene which is two-dimensional material has excellent mechanical, chemical, thermal properties, and many application areas such as energy storage devices, gas adsorption, sensing devices, and optical electronics. Further, graphene oxide (GO) is examined as a good adsorbent because of its important features such as functional groups (epoxy, carboxyl and hydroxyl) on the surface and layered structure. The SO2 adsorption properties of the fibers are usually investigated on carbon fibers. In this study, potential adsorption capacity of GO fibers was researched. GO dispersion was first obtained with Hummers’ method from graphite, and then GO fibers were obtained via wet spinning process. These fibers were converted into a disc shape, dried, and then subjected to SO2 gas adsorption test. The SO2 gas adsorption capacity of GO fiber discs was investigated in the fields of utilization of different coagulation baths and reduction by hydrazine hydrate. As coagulation baths, single and triple baths were used. In single bath, only ethanol and CaCl2 (calcium chloride) salt were added. In triple bath, each bath has a different concentration of water/ethanol and CaCl2 salt, and the disc obtained from triple bath has been called as reference disk. The fibers which were produced with single bath were flexible and rough, and the analyses show that they had higher SO2 adsorption capacity than triple bath fibers (reference disk). However, the reduction process did not increase the adsorption capacity, because the SEM images showed that the layers and uniform structure in the fiber form were damaged, and reduction decreased the functional groups which SO2 will be attached. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) analyzes were performed on the fibers and discs, and the effects on the results were interpreted. In the future applications of the study, it is aimed that subjects such as pH and additives will be examined.
 Y. İlhan, “Baca gazı kükürt gidermede doğal soda külü üretim süreci atığının kullanımının araştırılması (Master’s Thesis)”, Ankara University, Ankara, 2012, pp. 8-10.
 C. Chen, K. Xu, X. Ji, L. Miao, and J. Jiang, “Enhanced adsorption of acidic gases (CO2, NO2 and SO2) on light metal decorated graphene oxide”, Phys.Chem.Chem.Phys., vol. 16, pp. 11031-11036, 2014.
 C. L. Manguna, J. A. DeBarrb, J. Economya, “Adsorption of sulfur dioxide on ammonia-treated activated carbon fibers”, Carbon, vol. 39, pp. 1689–1696, 2001.
 Y. W. Lee, J. W. Park, J. H. Choung, D. K. Choi, “Adsorption characteristics of SO2 on activated carbon prepared from coconut shell with potassium hydroxide activation”, Environ. Sci. Technol., vol. 36, no. 5, pp. 1086-1092, 2002.
 N. Uçar, Z. Cavdar, N. Karatepe, P. Altayı, N. Kızıldağ, “SO2 adsorption capability of activated carbon nanofibers produced by different activation process parameters”, Tekstil ve Konfeksiyon, vol. 26, no. 4, pp.407-413, 2016.
 P. Zhang, H. Wanko, J. Ulrich, “Adsorption of SO2 on activated carbon for low gas concentrations”, Chemical Engineering Technology, vol. 30, no. 5, pp. 635-641, 2007.
 H. Tseng, M. Wey, “Study of SO2 adsorption and thermal regeneration over activated carbon-supported copper oxide catalysts”, Carbon, vol. 42, no. 11, pp. 2269-2278, 2004.
 D. J. Babu, F. G. Kühl, S. Yadav, D. Markert, M. Bruns, M. J. Hampeb and J. J. Schneider, “Adsorption of pure SO2 on nanoscaled graphene oxide”, Royal Society of Chemistry Adv., vol. 6, pp. 36834-36839, 2016.
 S. Hummers, S. William.R. E. Offeman, “Preparation of graphitic oxide”. Journal of the American Chemical Society. vol. 80, no. 6, pp. 1339, 1958.
 R. Kumar, D. K Avasthi., A. Kaur, “Fabrication of chemiresistive gas sensors based on multistep reduced graphene oxide for low parts per million monitoring of sulfur dioxide at room temperature”, Sensors and Actuators B: Chemical, vol. 242, pp. 461–468, 2017.
 V. Loryuenyong., K. Totepvimarn, P. Eimburanapravat, W. Boonchompoo, and A. Buasri, “Preparation and characterization of reduced graphene oxide sheets via water-based exfoliation and reduction methods,” Advances in Materials Science and Engineering, vol. 2013, Article ID 923403, 5 pages, 2013. doi:10.1155/2013/923403.
 M. J. Fernández-Merino, L. Guardia, J. I. Paredes, S. Villar-Rodil, P. Solís-Fernández, A. Martínez-Alonso and J. M. D. Tascón, “Vitamin C is an ideal substitute for hydrazine in the reduction of graphene oxide suspensions”, J. Phys. Chem. C, vol. 114, no. 14, pp. 6426–6432, 2010.