title: Ciprofloxacin adsorption on graphene and granular activated carbon: kinetics, isotherms, and effects of solution chemistry.
abstract: Ciprofloxacin (CIP) is a commonly used antibiotic and widely detected in wastewaters and farmlands nowadays. This study evaluated the efficacy of next-generation adsorbent (graphene) and conventional adsorbent (granular activated carbon, GAC) for CIP removal. Batch experiments and characterization tests were conducted to investigate the adsorption kinetics, equilibrium isotherms, thermodynamic properties, and the influences of solution chemistry (pH, ionic strength, natural organic matter (NOM), and water sources). Compared to GAC, graphene showed significantly faster adsorption and reached equilibrium within 3 min, confirming the rapid access of CIP into the macroporous network of high surface area of graphene as revealed by the Brunner-Emmet-Teller measurements analysis. The kinetics was better described by a pseudo-second-order model, suggesting the importance of the initial CIP concentration related to surface site availability of graphene. The adsorption isotherm on graphene followed Langmuir model with a maximum adsorption capacity of 323 mg/g, which was higher than other reported carbonaceous adsorbents. The CIP adsorption was thermodynamically favourable on graphene and primarily occurred through π - π interaction, according to the FTIR spectroscopy. While the adsorption capacity of graphene decreased with increasing solution pH due to the speciation change of CIP, the adverse effects of ionic strength (0.01-0.5 mol L(-1)), presence of NOM (5 mg L⁻¹), and different water sources (river water or drinking water) were less significant on graphene than GAC. These results indicated that graphene can serve as an alternative adsorbent for CIP removal in commonly encountered field conditions, if proper separation and recovery is available in place.
authors.affiliation: a SYSU-HKUST Research Center for Innovative Environmental Technology , School of Environmental Science and Engineering, Sun Yat-sen University , Guangzhou 510275 , People's Republic of China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhu
authors.affiliation: b Department of Civil and Environmental Engineering , Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong , People's Republic of China.
authors.forename: Daniel C W
authors.initials: DC
authors.lastname: Tsang
authors.affiliation: c Foshan Water Group , Foshan 52800 , People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.affiliation: a SYSU-HKUST Research Center for Innovative Environmental Technology , School of Environmental Science and Engineering, Sun Yat-sen University , Guangzhou 510275 , People's Republic of China.
authors.forename: Shiyu
authors.initials: S
authors.lastname: Li
authors.affiliation: a SYSU-HKUST Research Center for Innovative Environmental Technology , School of Environmental Science and Engineering, Sun Yat-sen University , Guangzhou 510275 , People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002606:Charcoal / Q000737:chemistry*; D002939:Ciprofloxacin / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D007700:Kinetics; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D002606:Charcoal; D002939:Ciprofloxacin; D006108:Graphite
keywords: adsorption; antibiotics; graphene; nanomaterials; water treatment