title: Impact of concentration and species of sulfamethoxazole and ofloxacin on their adsorption kinetics on sediments.
abstract: Antibiotics are used widely in human and veterinary medicine and are ubiquitous in environmental matrices worldwide. The influence of the concentration of antibiotics on adsorption kinetics is still unclear. This study used sulfamethoxazole (SMX) and ofloxacin (OFL) as adsorbates to investigate the adsorption kinetics on sediment affected by varying concentrations of antibiotics adsorbable species. At the experimental pH values, the major adsorbed species of SMX and OFL on sediment were SMX0and OFL+by hydrophobic interaction and electrostatic attraction, respectively. The apparent adsorption rate of SMX was not affected by the initial concentration and the pH values because the hydrophobic interactions were concentration-independent and charge-independent. However, the apparent adsorption rate of OFL significantly slowed down as the initial concentration increased. The adsorbed OFL+effectively neutralized the negative charges of the sediment, leading to a reduced adsorption rate of subsequent OFL+. The neutralization effect was greatly enhanced due to the increased OFL+with the increasing OFL concentration. Additionally, the apparent adsorption rate of OFL significantly increased at higher pH due to the reduced neutralization effect that resulted from the decreased OFL+and increased negative charges of the sediment surface. This study implied that the adsorption kinetics of antibiotics was greatly dominated by the concentration of adsorbable species rather than apparent overall concentration.
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China. Electronic address: zhangdi2002113@sina.com.
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Yunnan Institute of Food Safety, Kunming University of Science & Technology, Kunming, 650500, China.
authors.forename: Huang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
authors.forename: Saikat
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Pan
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D015242:Ofloxacin / Q000737:chemistry*; D013420:Sulfamethoxazole / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D015242:Ofloxacin; D013420:Sulfamethoxazole
keywords: Adsorbable species; Charge neutralization; Fast adsorption; Hydrophobic interaction; Slow adsorption