title: Adsorption isotherm, kinetic and mechanism of expanded graphite for sulfadiazine antibiotics removal from aqueous solutions.
abstract: The adsorption of sulfadiazine from water by expanded graphite (EG), a low cost and environmental-friendly adsorbent, was investigated. Several adsorption parameters (including the initial sulfadiazine concentration, contact time, pH of solution, ionic strength and temperature) were studied. Results of equilibrium experiments indicated that adsorption of sulfadiazine onto EG were better described by the Langmuir and Tempkin models than by the Freundlich model. The maximum adsorption capacity is calculated to be 16.586 mg/g at 298 K. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle models. The results indicated that the adsorption process followed pseudo-second-order kinetics and may be controlled by two steps. Moreover, the pH significantly influenced the adsorption process, with the relatively high adsorption capacity at pH 2-10. The electrostatic and hydrophobic interactions are manifested to be two main mechanisms for sulfadiazine adsorption of EG. Meanwhile, the ionic concentration of Cl-slightly impacted the removal of sulfadiazine. Results of thermodynamics analysis showed spontaneous and exothermic nature of sulfadiazine adsorption on EG. In addition, regeneration experiments imply that the saturated EG could be reused for sulfadiazine removal by immersing sodium hydroxide.
authors.affiliation: a School of Environmental and Chemical Engineering , Shanghai University , Shanghai , People's Republic of China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: a School of Environmental and Chemical Engineering , Shanghai University , Shanghai , People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: a School of Environmental and Chemical Engineering , Shanghai University , Shanghai , People's Republic of China.
authors.forename: SuWan
authors.initials: S
authors.lastname: Jin
authors.affiliation: a School of Environmental and Chemical Engineering , Shanghai University , Shanghai , People's Republic of China.
authors.forename: QunZan
authors.initials: Q
authors.lastname: Lu
authors.affiliation: b XiaMen JiangTian Membrane Biotechnology Ltd , Xiamen , People's Republic of China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Ji
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D006108:Graphite; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012996:Solutions; D013411:Sulfadiazine / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D000900:Anti-Bacterial Agents; D012996:Solutions; D014874:Water Pollutants, Chemical; D013411:Sulfadiazine; D006108:Graphite
keywords: Expanded graphite (EG); adsorption; mechanism; regeneration; sulfadiazine