Adsorption Characteristics of Cetirizine on Graphene Oxide

Water pollution caused by emerging contaminants such as pharmaceutical compounds is a growing problem worldwide. In this reported work, graphene oxide (GO) was directly used to remove an antihistamine drug, cetirizine. GO was prepared from graphite using a modified Hummer's method and was characterized by UV-vis spectroscopy, Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), field scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), etc. GO was demonstrated to be a highly efficient adsorbent for removing cetirizine from an aqueous solution. The adsorption of cetirizine on GO at various pH levels showed that in acidic pH with the adsorption shows faster kinetics and complete removal of cetirizine within 10 min, followed by neutral pH, which showed relatively slower kinetics but complete removal of cetirizine. However, at basic pH, GO could not completely remove cetirizine after 24 h. At a neutral pH, GO showed maximum adsorption of 81.30 mg g-1 of cetirizine. The adsorption isotherm results showed good agreement with the Langmuir isotherm. The BET surface area analysis showed the presence of mesoporosity in GO. In addition, the BET analysis further revealed a type IV isotherm curve being followed. A plausible mechanism is also discussed in the paper. The recyclability experiment demonstrates an adsorption efficiency of 85% after four cycles. The thermodynamic study reveals that adsorption is thermodynamically less favorable at higher temperatures. Hence, the current study successfully demonstrates the use of GO as an efficient adsorbent in removing cetirizine. It also studies the various factors and interactions affecting adsorption. Thus, this study sheds light on the adsorption characteristics of cetirizine on graphene oxide.