RESEARCH ARTICLE Removal of fluoroquinolone from aqueous solution using graphene oxide: experimental and computational elucidation Sarita Yadav 1 & Neetu Goel 1 & Vinod Kumar 2 & Kulbhushan Tikoo 2 & Sonal Singhal 1 Received: 31 July 2017 /Accepted: 24 October 2017 # Springer-Verlag GmbH Germany 2017 Abstract The environmental risks of antibiotics have attracted increasing research attention due to their prevalence and per- sistence in the aquatic environment. In this study, oxygen func- tionalized graphene, namely, graphene oxide (GO), was syn- thesized by modified Hummer’ s and Offeman’ s method and used as potential effective absorbent for the removal of fluoroquinolones (FQs), i.e., ciprofloxacin (CIP), norfloxacin (NOR), and ofloxacin (OFL), from aqueous solution. The as- synthesized GO was characterized by Fourier transform infra- red (FTIR) spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and high-resolution trans- mission electron microscopy (HRTEM). Out of various factors that were taken to consideration while studying the adsorption process, it was found that pH of antibiotic solution is more crucial than the other experimental parameters such as initial antibiotic concentration, contact time, and adsorbent dosage and has significant impact on FQ adsorption via the GO adsor- bent. The maximum removal of FQ was observed at pH 7 for CIP and NOR, while adsorption was maximum at pH 4 for OFL. Experimental data best fitted to the pseudo-second-order model as compared to the pseudo-first-order kinetic adsorption model. Best fitting of the equilibrium experimental data to Langmuir isotherm compared to Freundlich isotherm models established that FQ adsorbs over the GO in monolayer manner. Density functional theory (DFT) calculations performed at B3LYP/6-31G(d) level of theory in order to elucidate the ther- modynamic feasibility of adsorption process and nature of in- teractions of antibiotic molecules with the GO adsorbent. Keywords GO adsorbent . Antibiotics . Adsorption . Isotherm . Kinetic models . Density functional theory Introduction Fluoroquinolones (FQs) such as ciprofloxacin (CIP), norfloxacin (NOR), and ofloxacin (OFL) are the antibacterial synthetic drugs, commonly used in humans and animals as these drugs are safe with good tolerance limit and have high potency and broad antibacterial spectra (Park et al. 2007; Samuelsen 2006). However, FQs are poorly metabolized and are largely excreted from humans or animals in their pharma- cologically active forms (Ji et al. 2013; Schlüsener and Bester 2006; Sukul and Spiteller 2006; Sukul et al. 2009). According to previous reports, most frequently detected antibiotics all over the world are FQs, followed by sulfonamides, tetracy- clines, and macrolides (Lindberg et al. 2005; Verlicchi et al. 2010) in surface waters, domestic wastewater, municipal wastewaters, wastewater treatment plant (WWTP) effluents, and effluents from drug manufacturers (Joakim et al. 2007; Renew and Huang 2004; Watkinson et al. 2009; Xu et al. 2009). The high exploitation of FQs across the world has Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-017-0596-8) contains supplementary material, which is available to authorized users. * Neetu Goel neetugoel@pu.ac.in * Sonal Singhal sonal1174@gmail.com; sonal@pu.ac.in 1 Department of Chemistry, Panjab University, Chandigarh 160014, India 2 HR-TEM Facility Laboratory, National Institute of Pharmaceutical Education and Research (NIPER), SAS, Nagar, Punjab 160062, India Environ Sci Pollut Res https://doi.org/10.1007/s11356-017-0596-8