Ciprofloxacin Desorption Research Articles

Coupled effects of pH and kaolinite colloids on antibiotic transport in porous media

Antibiotics can interact with natural colloids and the surrounding media upon entry into soil and groundwater systems, which significantly alters their dynamic behavior and complicates our understanding of antibiotic fate and transport in porous media. In this study, co-transport of antibiotics and kaolinite colloids was systematically investigated using combined column experiments and numerical simulation under different pH conditions. Sulfadiazine (SDZ) transport was enhanced by kaolinite colloids under neutral and alkaline conditions, which was attributed to the higher mobility of colloids as SDZ carriers, as well as competitive sorption. However, most injected SDZ was transported in a dissolved form owing to the low sorption capacity of SDZ to kaolinite colloids and quartz sand. The colloid-facilitated transport model provided a good description of total SDZ transport, but underestimated colloidal SDZ transport using parameters from kinetic sorption experiments. Kaolinite colloids significantly promoted ciprofloxacin (CIP) transport at pH 4.0, but inhibited it at pH 7.0 and 9.0. Interestingly, enhanced CIP transport was due to the decreased number of effective sorption sites on quartz sand and the increased desorption of CIP from kaolinite colloids. Under neutral and alkaline conditions, deposited colloids provided additional sorption sites for CIP, which contributed to CIP retention. Moreover, CIP significantly inhibited the transport of kaolinite colloids owing to the increases in colloidal aggregate size and zeta potential. Overall, our results highlighted the different effects of mobile and immobile colloids on antibiotic transport, in addition to the implications of antibiotic speciation and clay colloids when predicting the transport behavior of these compounds.

Innovative sequential combination of fixed bed adsorption/desorption and photocatalysis cost-effective process to remove antibiotics in solution

In this paper, a Reed-based composite (R) beads, combined with photocatalysis, for the oxidative degradation of fluoroquinolones ciprofloxacin (CIP) in simulated hospital wastewater was developed. It is well known that hospital effluents present very diluted pollution (less than 5 mg/L), The first purpose, which concerns the first step to treat CIP solution (4 mg/L) via adsorption on (R) beads in continuous column system. The second aim was to regenerate the material for the simultaneous R reuse and CIP desorption in a low volume of a highly concentrated solution (≈30 mg/L). The third purpose was to degrade the concentrated solution of antibiotic using continuous and batch photocatalytic reactors. After CIP uptake on R-beads, two acid solutions were investigated for the regeneration step. Indeed desorption process was investigated using acetic acid (0.1 M) and hydrochloric acid (0.1 M) as eluents, leading to a highly concentrated CIP solution (≈30 mg/L) compared to the feed solution (4 mg/L). Consequently, these results provide new study into the application of sequential combination to effectively mineralize antibiotics with continuous treatment.

Antibiotic Adsorption by Acid Enhanced Dialium guineense Seed Waste

The pollution of water bodies with ciprofloxacin (CF) and other antibiotics has resulted in undesirable characteristics, such as color, odor and microbial resistance in environmental waters. Using agricultural waste as biosorbents for the removal of antibiotics from wastewater is a promising treatment approach. This research was based on the treatment of CF-polluted water by utilizing acid-modified Dialium guineense (tamarind) seed waste (HA-DGS), prepared by hydrochloric acid treatment of Dialium guineense seed (DGS). HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. The DGS and HA-DGS were characterized by the FTIR, SEM, EDX, TGA and BET analyses. The acid modification was optimized by the application of response surface methodology using central composite design. Batch methodology showed that HA-DGS had higher CF uptake than DGS at variations of pH, temperature, contact time, adsorbent dosage and CF concentration. The Freundlich isotherm with R2 > 0.9795 was more applicable to both adsorbents, while DGS conformed to the pseudo-second-order kinetic (R2 > 0.9939) and HA-DGS (R2 > 0.9085), to the pseudo-first-order kinetics. Thermodynamics showed a physical and exothermic uptake of CF on the adsorbents. HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. Quantum chemical parameters and condensed Fukui functions revealed efficient interaction between CF molecules and the prepared materials. Over 60% desorption of CF was obtained from the CF-loaded adsorbents using water and HCl solution. The results of this research showed HA-DGS as an efficient, low-cost, waste material that can be optimally valorized in the treatment of wastewater contaminated with CF.

Biosorptive interaction of alkaline modified Dialium guineense seed powders with ciprofloxacin in contaminated solution: central composite, kinetics, isotherm, thermodynamics, and desorption

This work evaluated the use of Dialium guineense seed waste (DGS) and its sodium hydroxide modified form (NH-DGS) as biosorbent for ciprofloxacin (CPF) from synthetic solution as well as the desorption potentials. Central composite design (CCD) was applied for optimization of the alkaline treated biosorbent by response surface methodology using design expert. Both biosorbents were characterized by FTIR, SEM, EDX, and BET analysis. The CCD showed NaOH concentration of 0.46 M and temperature of 96 °C to be effective for optimized modification of NH-DGS. Optimum removal of CPF was obtained at pH 6.0, contact time 120 min, temperature 300 K, and dosage of 0.1 g. The Freundlich model gave the best fit compared to the other isotherms tested with R2 values >0.97951. NH-DGS exhibited a maximum uptake capacity of 120.34 mg/g higher than some reported adsorbents for CPF. The pseudo-second-order model was suitable in the fitting of the kinetic data. A non-spontaneous process was obtained for CPF biosorption on DGS which became spontaneous after alkaline treatment. Over 84% desorption of CPF was achieved on both biosorbents using 0.3 M HCl which envisaged the use of NH-DGS as an efficient material for treatment of waters contaminated with CPF.

Stress-responses of activated sludge and anaerobic sulfate-reducing bacteria sludge under long-term ciprofloxacin exposure

The activated sludge (AS) and sulfate-reducing bacteria (SRB) sludge systems were continuously operated for 200 days in laboratory to investigate the stress-responses of these two sludge systems under ciprofloxacin (CIP) exposure. It was found that CIP was effectively removed by SRB sludge via adsorption and biodegradation, but little biodegradation in AS system. The CIP biodegradation by SRB sludge made the SRB sludge system more sustainable and tolerant to long-term CIP exposure than AS system with significant (p < 0.05) CIP desorption and decrease of CIP removal. CIP shaped the microbial communities in AS and SRB sludge, and significantly (p < 0.05) inhibited the family Nitrosomonadaceae (ammonia-oxidizing bacteria (AOB)) and genus Nitrospira (nitrite-oxidizing bacteria (NOB)/complete ammonia oxidizer(comammox)) and the nitrogen removal in AS system. Moreover, CIP posed the increase of genus Zoogloea-like organisms and the non-filamentous bulking of AS, e.g. 313 ± 12 mL/g of sludge volume index (SVI) at phase V (influent CIP = 5000 μg/L). The genus Desulfobacter was enriched in SRB sludge system under long-term CIP exposure, and stimulated chemical oxygen demand (COD) removal and sulfate reduction. The increase of genera Zoogloea, Acinetobacter and Flavobacterium in AS, and Zoogloea and Acinetobacter in SRB sludge systems under CIP exposure promoted extracellular polymeric substances (EPS) production and CIP adsorption for self-protection of microbes against CIP toxicity. The functional groups of N–H, O–H, C–O–C and C=O in EPS of AS and SRB sludge provided adsorption sites for CIP and impeded CIP impact on microbial cells. The findings of this study provide an insight into the stress-responses of AS and SRB sludge under long-term CIP exposure, and exhibit the great potential of treating CIP-laden wastewater by SRB sludge system.

Ciprofloxacin desorption from gel type ion exchange resin: Desorption modeling in batch system and fixed bed column

The aim of this paper was to assess the desorption of ciprofloxacin (CIP) from the Supergel™ SGC650H resin and to evaluate the possibility of future reuse of the adsorbent by applying adsorption cycles. Preliminary desorption tests by using different aqueous HCl concentrations as eluent agents and adsorption experiments with the previously treated resin with these same solutions were carried out in batch system to determine the best eluent condition. Physico-chemical characterization tests were performed for virgin and HCl-treated resin, evidencing changes on the resin’s structure and functional groups caused by the eluents. The preliminary results showed that the HCl concentration of 2 mol L−1 provided both the CIP-desorption efficiency from the resin and the improvement of CIP adsorption capacity. Therefore, this eluent concentration was applied for the further equilibrium experiments in batch system. Mathematical modeling was applied to the kinetic and equilibrium desorption data obtained in batch system, evidencing that internal diffusion model showed a good agreement with the experimental data. Based on the estimated parameters from the independent batch experiments, the model was able to adequately predict the desorption kinetic behavior in fixed bed column. Overall, the results showed that the HCl aqueous solution of 2 mol L−1 could be efficiently applied to assess adsorption cycles, due to the high desorption efficiency combined with the enhancement of the resin’s capacity. Furthermore, the present work provided a robust and predictive mathematical model, which could support the design and the scale up of industrial level equipment.

Insights into the use of metal complexes of thiourea derivatives as highly efficient adsorbents for ciprofloxacin from contaminated water

Despite the wide use of synthesised metal complexes of thiourea and their derivatives in medicine and corrosion inhibition, a paucity of research exists on their application as adsorbents for pollutants. This study was aimed at investigating the adsorption potential of the copper (II) and zinc (II) complexes of 4-nitro-substituted thiourea derivatives of aminophenol for ciprofloxacin (CPF). The metal complexes were synthesised and characterised. Fourier transform infrared spectroscopy, scanning electron microscopy and a BET surface area analyzer were utilised to determine the surface structure and properties of the synthesised adsorbents. Isotherms were conducted by the application of Langmuir, Freundlich and Scatchard models and revealed a heterogeneous multilayer adsorption process. Kinetic evaluation showed best fit with the pseudo second order model (R2 > 0.991) compared to the pseudo first order and Bangham equations. Thermodynamics showed an endothermic spontaneous abstraction process. The metal complexes showed over 80% desorption of CPF using 0.2 M NaOH and were stable over three cycles of regeneration and reuse. This research revealed the potential of the metal complexes of thiourea as adsorbents for CPF supported by the high adsorption capacity compared to other reported adsorbents.

Cation-Pi Interaction: A Key Force for Sorption of Fluoroquinolone Antibiotics on Pyrogenic Carbonaceous Materials.

Cation-pi attraction is a major force that determines macromolecular structures and drug-receptor interactions. However, the role of the cation-pi interaction in sorption of fluoroquinolone antibiotics by pyrogenic carbonaceous materials (PCMs) has not been addressed. We studied sorption of ciprofloxacin (CIP) on graphite to quantify the contribution of the cation-pi interaction. Through competition experiments, the decreased amount of sorbed CIP by sequential treatment with hexadecane, phenanthrene and benzylamine represents the contribution of hydrophobic, pi-pi and cation-pi interactions, respectively. Benzylamine competed more strongly with CIP than n-hexadecane and phenanthrene, indicating that cation-pi is a major force. Cation-pi interactions accounted for up to 72.6% of the total sorption at an initial CIP concentration of 0.000015 mmol/L. Importantly, species transformation (CIP(0) captures H+ from water to form CIP(+1)) induced by cation-pi interactions was verified both experimentally and theoretically and can be used to explain the environmental behavior of other fluoroquinolone antibiotics and biochemical processes of amino acids that interact with aromatic moieties. Because of the significant role of cation-pi interactions, CIP desorption increased up to 2.32 times when Na+ increased from 0.01 mM to 0.45 mM, which is an environmentally relevant scenario at river estuaries. Hence, behaviors of fluoroquinolone antibiotics that are affected by ionic strength changes need to be carefully evaluated, especially in river estuaries.

Preparation of magnetic MIL-101 (Cr) for efficient removal of ciprofloxacin.

Metal organic frameworks are widely used as adsorbent materials in recent years. In this study, the most prepared metal organic framework MIL-101 was prepared by hydrothermal method and featured magnetic property using co-precipitation method Fe3O4. Then, the prepared composite (MIL-101/Fe3O4) was first characterized using XRD, FTIR, SEM-EDS, and surface area analysis, then was used for the adsorptive removal of the most used antibiotic, ciprofloxacin (CIP). The effect of different adsorption variables which may affect the removal of CIP by MIL-101/Fe3O4 was investigated, as well as their adsorbent quantity, initial CIP concentration, pH, temperature, and contact time. The non-linear Langmuir and Freundlich isotherm were applied to experimental data. It was observed that rising solution temperature decreases adsorption efficiency, as the maximum adsorption uptake value was 63.28mgg-1 at 298K and 22.93mgg-1 at 313K, indicating the exothermic nature of the adsorption. The adsorption was studied kinetically and found to follow the pseudo-second-order kinetic model. The desorption of CIP from the MIL-101/Fe3O4 was investigated using three different eluents, and the results showed that phosphate-buffered solution was the most effective desorption eluent. Graphical abstract Schematic diagram of the preparation steps of MIL-101/Fe3O4.

Low-molecular-weight organic acids correlate with cultivar variation in ciprofloxacin accumulation in Brassica parachinensis L.

To understand the mechanism controlling cultivar differences in the accumulation of ciprofloxacin (CIP) in Chinese flowering cabbage (Brassica parachinensis L.), low-molecular-weight organic acids (LMWOAs) secreted from the roots of high- and low-CIP cultivars (Sijiu and Cutai, respectively) and their effects on the bioavailability of CIP in soil were investigated. Significant differences in the content of LMWOAs (especially maleic acid) between the two cultivars played a key role in the variation in CIP accumulation. Based on the Freundlich sorption coefficient (Kf) and distribution coefficient (Kd), the presence of LMWOAs reduced the CIP sorption onto soil particles, and higher concentrations of LMWOAs led to less CIP sorption onto soil. On the other hand, LMWOAs enhanced CIP desorption by lowering the solution pH, which changed the surface charge of soil particles and the degree of CIP ionization. LMWOAs promoted CIP desorption from soil by breaking cation bridges and dissolving metal cations, particularly Cu2+. These results implied that the LMWOAs (mainly maleic acid) secreted from Sijiu inhibited CIP sorption onto soil and improved CIP desorption from soil to a greater extent than those secreted from Cutai, resulting in higher bioavailability of CIP and more uptake and accumulation of CIP in the former.

Adsorption of antibiotic ciprofloxacin on carbon nanotubes: pH dependence and thermodynamics

The environmental risks of antibiotics have attracted increasing research attention, but their environmental behaviors remain unclear. In this study, functionalized carbon nanotubes (CNTs), namely, hydroxylized (MH), carboxylized (MC), graphitized multi-walled CNTs (MG) and single-walled CNTs (SW) were used as adsorbents and ciprofloxacin (CIP) as an adsorbate to investigate the effect of pH and temperature on sorption and desorption processes. Sorption isotherms of CIP were fitted well by Freundlich and Dubinin–Ashtakhov models. Highly nonlinear isotherms of CIP were observed, indicating the highly heterogeneous site energy distribution on CNTs. At all pHs, SW had the highest sorption for CIP due to its largest surface area among all CNTs. Sorption distinction between MH and MC was explained by π–π electron donor–acceptor interactions. For SW, CIP sorption was thermodynamically favorable and endothermic associated with an entropy driven process, while the reverse process occurred for MC and MG. The rearrangement of CNTs bundles/aggregates and covalent bond formation may be responsible for CIP desorption hysteresis on CNTs. Desorption of antibiotics from CNTs may lead to potential exposure, particularly under changing environmental conditions such as temperature and pH.

Desorption of ciprofloxacin from clay mineral surfaces

Desorption from soil clay components may affect the transport and fate of antibiotics in the environment. In this study, ciprofloxacin (CIP) desorption from a kaolinite and a montmorillonite was investigated under different pHs, different concentrations of metal cations of various valencies (Na+, Ca2+ and Al3+) and a cationic surfactant hexadecyltrimethylammonium (HDTMA), and different desorption cycles. Desorption of CIP from kaolinite and montmorillonite was strongly pH-dependent and desorption isotherms were well fitted with the Langmuir equation. The percentage of CIP desorbed increased with increasing initial CIP loadings, desorbing cation concentrations, and desorption cycles. Comparatively, CIP was more readily desorbed from kaolinite than from montmorillonite. Moreover, the hysteresis index values were all negative, suggesting that the presence of metal cations and HDTMA in solution promoted CIP desorption from clay minerals, owing to cation exchange. The XRD analyses indicated that desorption of CIP occurred from both external and interlayer surfaces of montmorillonite. Formation of Al–CIP complex on solid surface and then detachment of Al–CIP from the solid surface may contribute to the higher CIP desorption by Al3+ in comparison to Na+ and Ca2+.