Adsorption of Fluoroquinolone Antibiotics at the Gas–Liquid Interface Using Ionic Surfactants

Abstract

The overuse of antibiotics in today's society has resulted in high concentrations of pharmaceutical contaminants in the natural environment. In this work, we investigated the surfactant-mediated adsorption of fluoroquinolone (FQ) antibiotics at the gas−liquid interface and their separation using a semi-batch foam fractionation process. FQs being a zwitterionic compound have an affinity to bind with both cationic and anionic surfactants. The adsorption of FQs to the gas−liquid interface was investigated using a cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) surfactant. Ciprofloxacin (CF) was chosen as a model FQ antibiotic. The adsorption properties of the surfactant systems and CF were characterized using pendant-drop tensiometry and surface excess analysis. It was found that CF partitions to the gas−liquid interface more readily in the presence of SDS compared to CTAB. This was also corroborated in the foam fractionation experiments. At optimum operating conditions, CF showed a higher removal efficiency with SDS (96.3%) compared to CTAB (52%). In spite of strong molecular interactions between CTAB and CF, the preferential adsorption of DS − −CF complexes was far greater than CTA + −CF complexes. At optimized operating conditions, using SDS as the surfactant, other FQs such as norfloxacin, levofloxacin, and ofloxacin were recovered up to 97.9, 91.7, and 96.7%, respectively, with effluent concentration less than 100 nM. Overall, the work demonstrates foam fractionation as a novel and environment-friendly gas− liquid separation technique for the targeted removal of FQ antibiotics from waterbodies.

Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater

“…CTAB electrostatically interacts with the charged headgroup of short-chain PFAS, while the hydrophobic tail of CTAB interacts with the hydrophobic tails of PFAAs, resulting in an increased level of accumulation of the short chains at the plasma−liquid interface, exposing these compounds to the reactive species formed by the plasma. 17,18 In these experiments, the concentration of PFHxA decreased to below detection limits within 30 min, the concentrations of PFPeS and PFPeA were <50 ng/L after 60 min, the concentration of PFBA was <50 ng/L after 120 min, and the PFBS concentration reached a final concentration of 100 ng/L after 120 min (Figure 6). Overall, the total short-chain PFAA concentration was decreased by 88% in 120 min.…”

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis

“…The results indicate that [C 10 mim][BF 4 ] has more binding affinity with the drug owing to the presence of four highly electronegative fluorine atoms involved in attraction with the carboxylic and carbonyl moieties of CIP. Similar results have been proposed by Ghosh et al for the interaction of CIP with surfactants SDS and CTAB, and they agreed that electrostatic attraction plays a vital role in the interaction between CIP and SDS/CTAB molecules in aqueous medium . The associated interaction parameters for all of the IL–CIP interactions are summarized in Table , and they revealed that the binding processes are spontaneous in nature and entropy-driven.…”

“…56 and CTAB, and they agreed that electrostatic attraction plays a vital role in the interaction between CIP and SDS/CTAB molecules in aqueous medium. 39 The associated interaction parameters for all of the IL−CIP interactions are summarized in Table 2, and they revealed that the binding processes are spontaneous in nature and entropy-driven. The change in enthalpy and entropy values signifies that the bimolecular interaction between the drug and ILs is enthalpy−entropydependent.…”

“…They found that poorly water-soluble drugs have higher removal efficiency with SDS than with CTAB. The adsorption of poorly soluble drugs was due to complexation between the drug and the surfactant through ion-pair formation . Kurnik et al developed cholinium-IL-based amphiphilic polymeric micelles by utilizing Pluronic and various ILs in biphase micellar systems for hydrophobic drug delivery.…”

“…The adsorption of poorly soluble drugs was due to complexation between the drug and the surfactant through ion-pair formation. 39 Ciprofloxacin (CIP) is an antibacterial drug of second generation, which displays exceptional pharmacokinetic and antimicrobial properties. It is an extensively prescribed fluoroquinolone antibiotic and is widely utilized for the treatment of urinary, skin, and other bacterial diseases.…”