Adsorption Mechanisms Of Ciprofloxacin Research Articles

Highly efficient adsorption of ciprofloxacin from aqueous solutions by waste cation exchange resin-based activated carbons: Performance, mechanism, and theoretical calculation

This study focused on the preparation of a highly efficient activated carbon adsorbent from waste cation exchange resins through one-step carbonization to remove ciprofloxacin (CIP) from aqueous solutions. Scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the carbonized materials. The CIP removal efficiency, influencing factors, and adsorption mechanisms of CIP on the carbonized resins were investigated. Density functional theory (DFT) computations were performed to elucidate the adsorption mechanisms. The CIP removal reached 93 % when the adsorbent dosage was 300 mg/L at 25 °C. The adsorption capacity of the carbonized resins to CIP gradually decreased with an increasing pH from 3.0 to 7.0 and sharply declined with a pH from 7.0 to 11.0. The adsorption process better fitted by the pseudo second-order kinetic and Langmuir models, indicating that the interaction between CIP and the carbonized resins was monolayer adsorption. The maximum adsorption capacity fitted by the Langmuir model was 384.4 mg/g at 25 °C. Microstructural analysis showed that the adsorption of CIP on the carbonized resins was a joint effect of H-bonding, ion exchange, and graphite-N adsorption. Computational results signified the strong H-bonding and ion exchange interactions existed between CIP and carbonized resins. The high adsorption and reusability suggest that waste cation exchange resin-based activated carbons can be used as an effective and reusable adsorbent for removing CIP from aqueous solutions.

Unraveling the sorption mechanisms of ciprofloxacin on the surface of zeolite 4A (001) in aqueous medium by DFT and MC approaches

The adsorption mechanism of ciprofloxacin (CIP) and its ionic form were investigated using density functional theory (DFT) and molecular dynamics (MD), with the goal of forecasting their adsorption behavior in terms of gap energy, global reactivity descriptors, Fukui functions, adsorption energies, and density of state on the surface of zeolite 4A (001). Quantum chemical parameters related to the adsorption process were calculated, as well as the overall reactivity. According to DFT calculations, the zwetterionic form CIP± are the most stable and reactive and have a greater power of electron transfer compared to the other species. Under aqueous conditions, zeolite can adsorb ciprofloxacin (CIP) and its ionic forms, as revealed by molecular dynamics simulation. Ciprofloxacin in the zwitterionic form (CIP±) were more efficiently adsorbed to the surface of zeolite 4A (001) than the cationic (CIP+), anionic (CIP−), and neutral(CIP) forms; through the evaluation of adsorption energy, probability distribution, interaction, and density of state. The results also demonstrated that the compounds studied were adsorbed via the process of chemical bonding, which was confirmed by the negative values of the interaction energy. Furthermore, the negative adsorption energy values suggest a significant adsorption of all compounds, with electrostatic interactions (physisorption), diffusion into the pores, and n-π bonds (chemisorption) on the zeolite surface. The increase in adsorption energies and the proximity of the molecules studied to the zeolite surface indicate the predominance of chemisorption, and the adsorption of ciprofloxacin was found to be an exothermic and spontaneous process. Molecular dynamics (MD) modeling was in agreement with the DFT results.

Removal of ciprofloxacin from an aqueous medium by adsorption on natural and hydrolyzed bentonites

Two bentonites (sodic bentonite, BSN, and calcic bentonite, BCN) were treated with nitric acid to improve the adsorption capacities using ciprofloxacin (CIP) as an adsorbate. The results demonstrated that nitric acid treatment enhances the specific area and increases the pore volume of both bentonites. The mechanism of adsorption of CIP was investigated using a kinetic model, isotherms, and pH influence. The adsorption capacity for BSN increased from 294.1 mg.g−1 to 416.6 mg.g−1 after acid treatment, while the increase in the adsorption capacity of BCN was minor. The increase in CIP removal may be due to an increase in the specific area and the presence of acidic surface functional groups. The adsorption mechanism of CIP on all adsorbents was governed by external diffusion, internal diffusion, and adsorption to reach equilibrium. The adjustment of strong adsorbents to the BET model indicated multilayer adsorption. The best adsorbent is sodic bentonite with nitric acid treatment. The study of the pH effect showed that the mechanism of CIP adsorption is hydrogen bonds and electrostatic interaction. Therefore, the acid treatment was found promising to improve the adsorbent characteristic of clays for removing CIP from water.

RETRACTED: Controlled synthesis of porous Zn/Fe based layered double hydroxides: Synthesis mechanism, and ciprofloxacin adsorption

• porous Zn/Fe LDH exhibited appreciable adsorption capacity. • Successful decomposition of H 2 O 2 present between the LDH layers. • Introduction of pores in the layers enhanced the surface area and adsorption activity. • Successfully reusable for consecutive 6 cycles adsorption cycles. Present work include the designing of a novel porous Zn/Fe layered double hydroxide (LDH) based adsorbent using a combination of three methods, namely, co-precipitation, hydrothermal, and thermal treatment. The Zn/Fe LDH was synthesized by co-precipitation followed by hydrothermal method. The LDH was then intercalated with H 2 O 2 and its decomposition under the thermal treatment created oxygen bubbles that pierce holes in the layered structure of the LDH by local pressure build-up. Major techniques used for assessing the morphology and surface area characteristics of the LDH and porous LDH were Scanning electron microscope (SEM) and Brunauer-Emmet-Teller (BET). The intercalation of H 2 O 2 and its later decomposition triggered by thermal treatment lead to the introduction of pores in the LDH layers that increased the surface area from 108.863 m 2 /g to 168.923 m 2 /g. The synthesized adsorbent was utilized for the removal of an antibiotic; ciprofloxacin (CIP) from the aqueous solution. The porous Zn/Fe LDH adsorbent was featured with an admirable CIP adsorption capacity of 344.83 mg/g at pH 6.5 and temperature 298 K. The adsorption of CIP onto porous Zn/Fe LDH adsorbent followed the Freundlich isotherm model and pseudo-second-order kinetic model. The temperature increase negatively affected the adsorption rate. The adsorption mechanism of CIP onto porous Zn/Fe LDH was also projected and established, and Cπ- metal interactions, hydrogen bonding, and electrostatic interactions, were found to be the major interactive forces. The thermodynamic study revealed the exothermic and spontaneous nature of the adsorption experiments. Overall, the synthesized adsorbent is sustainable in terms of its usability and non-toxic nature.

A novel self-floating silica adsorbent for antibiotic ciprofloxacin and nickel (II) ion

A novel self-floating silica adsorbent was synthesized by introducing sulfonic acid groups onto the surface of hollow glass microsphere (HGM) through post-grafting technique. The obtained sulfonated HGM (SO3H-HGM) not only had satisfactory adsorption performance for ciprofloxacin (CIP) and heavy metal nickel (Ni2+), but also had stable self-floating capability. SO3H-HGM exhibited wide pH adaptability. Langmuir and Elovich models well fitted the adsorption isotherm and kinetic data, respectively. Under the optimal experimental conditions, the theoretical saturated adsorption capacities of SO3H-HGM for CIP and Ni2+ calculated by the Langmuir model reached 464.78 mg·g−1 and 19.65 mg·g−1, respectively. Thermodynamic calculation verified the spontaneous nature and feasibility of the adsorption processes. The saturated adsorbent could be easily desorbed and regenerated by the eluent, and after five adsorption cycles, there was no serious reduction in adsorption capacity, which proved the good reusability and stability of SO3H-HGM. The adsorption mechanism of CIP and Ni2+ by SO3H-HGM is mainly electrostatic interaction, followed by hydrogen bond, hydrophobic interaction and coordination. This research demonstrates that HGM is a potential and promising material for the adsorptive purification of water contaminated with CIP and Ni2+, and to realize self-floating solid–liquid separation.

Magnetic nickel cobalt sulfide/sodium dodecyl benzene sulfonate with excellent ciprofloxacin adsorption capacity and wide pH adaptability

In this study, a novel magnetic nickel cobalt sulfide/sodium dodecyl benzene sulfonate (FSNCS/SDBS) adsorbent was synthesized successfully by a facile protocol and was developed to remove ciprofloxacin (CIP) for water purification. The FSNCS/SDBS adsorbent is featured with excellent CIP adsorption capacity of 625 mg·g−1 (much higher than reported most adsorbents), wide pH adaptability (little changed CIP adsorption capacity in pH 6–11), and good magnetic property. The effects of pH and ionic strength on CIP adsorption were investigated. The calculative thermodynamic parameters indicated that CIP adsorption by FSNCS/SDBS was spontaneous and exothermic. CIP adsorption followed pseudo-second-order kinetics and an isotherm best fit with the Langmuir adsorption mode. The adsorption mechanism of CIP onto FSNCS/SDBS was proposed and demonstrated, which included the electrostatic interaction, π–π interaction, coordination with metal and hydrogen bonding.

Removal of Ciprofloxacin with Aluminum-Pillared Kaolin Sodium Alginate Beads (CA-Al-KABs): Kinetics, Isotherms, and BBD Model

In recent years, the problem of water pollution caused by antibiotics has attracted wide attention. The common use of antibiotics represents a threat to both human health and environmental safety. The modification of kaolin clay is promising due to its high efficiency, easy operation, and low cost. In this study, a novel material, aluminum-pillared kaolin sodium alginate beads (CA-Al-KABs), was synthesized by gelling and solidification processes. The structure and chemical properties were characterized by various analytical methods. The influencing factors (such as adsorbent dosage, contacting time, pH, ion strength, temperature, and initial concentration) and adsorption mechanism of ciprofloxacin (CIP) were studied. Furthermore, adsorption kinetics, adsorption isotherms, and a Box–Behnken design (BBD) model were conducted. Moreover, CA-Al-KABs’ adsorption efficiency towards other antibiotics were also evaluated. The adsorption experiments showed that the acidic environment (pH = 4) was more favorable for the adsorption of ciprofloxacin. The adsorption kinetics of ciprofloxacin by CA-Al-KABs microspheres were confirmed to be more suitable with the pseudo-first-order kinetics model. The Langmuir isotherm model showed that the maximum adsorption capacity of CA-Al-KABs microspheres to ciprofloxacin was 68.36 mg/g at 308.15 K. The adsorption driving force of CIP near CA-Al-KABs may be the electrostatic attraction. Further, CIP could also form complexes with Ca2+ and Al—Al—OH on CA-Al-KABs, and thus CIP was attracted to the adsorbent. Adsorption thermodynamics showed that the adsorption process was exothermic, feasible, and spontaneous. In addition, the adsorption performance on other antibiotics indicated CA-Al-KABs’ broad application in the treatment of antibiotic wastewater.

Adsorptive Removal of Antibiotic Ciprofloxacin from Aqueous Solution Using Protein-Modified Nanosilica.

The present study aims to investigate adsorptive removal of molecular ciprofloxacin using protein-modified nanosilica (ProMNS). Protein was successfully extracted from Moringa seeds while nanosilica was synthesized from rice husk. Fourier-transform infrared (FTIR), ultraviolet visible (UV-Vis) and high-performance liquid chromatography (HPLC) were used to evaluate the characterization of protein. Adsorption of protein onto nanosilica at different pH and ionic strength was thoroughly studied to modify nanosilica surface. The removal efficiency of antibiotic ciprofloxacin (CFX) increased from 56.84% to 89.86% after surface modification with protein. Effective conditions for CFX removal using ProMNS were systematically optimized and found to be pH 7.0, adsorption time 90 min, adsorbent dosage 10 mg/mL, and ionic strength 1 mM KCl. A two-step model was successfully used to fit the adsorption isotherms of CFX onto ProMNS at different ionic strength while a pseudo-second-order model could fit adsorption kinetic of CFX onto ProMNS very well. Maximum adsorption capacity was very high that reached to 85 mg/g. Adsorption of CFX onto ProMNS decreased with increasing KCl concentration, suggesting that adsorption of CFX onto ProMNS is mainly controlled by electrostatic attraction between positively charged ProMNS surface and anionic species of CFX. Adsorption mechanisms of CFX onto ProMNS were discussed in detail based on adsorption isotherms, the change in surface charge by zeta potentail and the change in functional groups by FT-IR. The removal of CFX after three regenerations was greater than 73% while CFX removal from an actual hospital wastewater using ProMNS reached to 70%. Our results suggest that ProMNS is a new and eco-friendly adsorbent to remove antibiotics from aqueous solutions.

Caffeine and Ciprofloxacin Adsorption from Water onto Clinoptilolite: Linear Isotherms, Kinetics, Thermodynamic and Mechanistic Studie

In this study, clinoptilolite was used to sequester ciprofloxacin (CIP) and caffeine (CAF), two emergent contaminants, from aqueous solution using batch equilibration method and the effects of contact time, pH, initial contaminant concentration, temperature and adsorbent dosage investigated and herein reported. The adsorption kinetics was described by the pseudo-second-order model (PSO) and pore diffusion was not the sole operative rate-controlling step as depicted by the intraparticle diffusion model. The equilibrium data were modelled using three linear forms of Langmuir equation and Freundlich model and was best fitted by the Lineweaver-Burk linearization of Langmuir equation (type-1). Linearization is shown to induce errors that may lead to discrepancies in parameter values estimation. The derived thermodynamic functions revealed the adsorption processes are exothermic, spontaneous and physical in nature. The adsorption mechanism of CIP is strongly controlled by electrostatic interactions while CAF adsorption is weakly affected by changes in pH. The findings demonstrate that clinoptilolite in its unmodified form is a potential low-cost and eco-friendly adsorbent for removal of pharma-ceutically active ingredients from water. Keywords: Caffeine, ciprofloxacin, adsorption, clinoptilolite, linear isotherms.

Adsorption Mechanisms of Ciprofloxacin by Extracellular Polymeric Substances of Sulfate-reducing Bacteria Sludge

Extracellular polymeric substances (EPS) in microbial sludge, fulfils a key role in removal of micro-organic pollutants during biological wastewater treatment. In this study, the authors evaluated the removal of ciprofloxacin (CIP) by sulfate-reducing bacteria (SRB) sludge in a sulfate-reducing up-flow sludge bed (SRUSB) reactor, and examined the role of EPS on CIP removal in an SRB sludge system. The results indicated that CIP was removed efficiently through adsorption and biodegradation by SRB sludge, with adsorption the major removal pathway. EPS also played an important role in CIP adsorption by SRB sludge, and the adsorption mechanisms of CIP by EPS were investigated using the three-dimensional excitation-emission matrix fluorescence spectroscopy technologies combined with parallel factor analysis. The functional groups binding CIP onto EPS were identified through Fourier transform infrared (FTIR) spectra analysis. The results suggested that the static quenching of EPS following CIP adsorption led to formation of an EPS-CIP complex, and that the CIP was mainly bound with tryptophan and tyrosine-like protein substances in EPS with the binding constants of 1.43×104 L·mol-1 and 1.02×104 L·mol-1, respectively. The FTIR results suggested that hydroxyl, amino and carboxyl functional groups were mainly responsible for binding of CIP onto EPS. The results revealed the adsorption mechanisms of CIP by EPS in SRB sludge, and enhanced understanding of the role of EPS in sulfur-mediated biological processes for the removal of CIP and other organic micro-pollutants.

Adsorption of ciprofloxacin on to bamboo charcoal: Effects of pH, salinity, cations, and phosphate

The adsorption of ciprofloxacin (CIP) by bamboo charcoal in aqueous solution was explored under varying pH, salinity, metal cations, and phosphate. The adsorption kinetics and adsorption isotherms were depicted well by the pseudo‐second‐order and Langmuir models, respectively. The maximum adsorption capacity ( ) was 36.02 mg g−1 according to the Langmuir model. The CIP adsorption increased with increasing pH and reached the maximum adsorption amount at pH 5.5, then decreased with increasing pH. It indicated that cation exchange played an important role in CIP adsorption. The effects of metal cations (0.2 mM Cu2+, Zn2+, Cd2+, Pb2+, and Al3+) on the CIP adsorption are both pH and cation species dependent. Al3+ greatly increased the CIP adsorption on to bamboo charcoal at pH 3.5, 5.5, and 9.5 (p < 0.05). Pb2+ inhibited the CIP adsorption, while Cu2+ significantly enhanced the CIP adsorption at pH 3.5 and 5.5, but both showed insignificant effects at pH 9.5. The presence of phosphate enhanced the CIP adsorption at pH 3.5 and 5.5, while slightly inhibiting the CIP adsorption at pH 9.5. The adsorption mechanisms of CIP on to bamboo charcoal were ascribed to cation exchange, hydrogen bonding and metal bridging. These results suggest that bamboo charcoal has great potential to be used as an efficient material in CIP removal from aquatic environments. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1108–1115, 2017

Influence of pH and antibiotic solubility on the removal of ciprofloxacin from aqueous media using montmorillonite

The ciprofloxacin (CPX) is a fluoroquinolone antibiotic that has been found in soils and aqueous media due to its vast use in both, human and veterinary health care. As a consequence the removal of this kind of compounds is widely studied. However, there are a few studies about the CPX removal from aqueous media by adsorption.This work is focused on the study of CPX removal by adsorption using an Argentinian montmorillonite (Mt). The influence of the pH media and the consequent antibiotic solubility in the adsorption process was analyzed. The experimental curve of CPX solubility versus pH media showed a strong correlation between them where the lowest value of solubility was obtained for the zwitterion species (CPX±). This result points out the fact that the solubility of the CPX species must be considered in adsorption experiments because of the antibiotic precipitation and the consequent overestimation of the adsorbent adsorption capacities. CPX adsorption kinetics and adsorption isotherms at different pH values showed that the adsorption processes obey pseudo-second order kinetics. The CPX adsorption capacity of the Mt, the affinity of the species towards its surface and the possible mechanisms involved in the adsorption process were assessed by Langmuir, Freundlich and Scatchard methods. The results showed that the adsorption mechanism of CPX on Mt is pH dependent, obtaining a negative cooperative mechanism at pH3, 6 and 7.5 and a positive cooperative mechanism at pH10. The highest CPX adsorption capacity on Mt was obtained at pH6. Infrared spectroscopy and X-ray diffractograms of the complexes obtained after the adsorption process provided information about the interaction between the functional groups of CPX and the adsorption sites on Mt and the changes in the basal space related with the molecular arrangements of the CPX on the sample, respectively. The CPX removal by this clay mineral is remarkably higher when it is compared with other materials and quite similar to previous data obtained with other bentonites.

Adsorption Mechanism of Ciprofloxacin from Water by Synthesized Birnessite

The efficiency of ciprofloxacin (CIP) adsorption on synthesized birnessite was systematically studied under varying physicochemical conditions, such as solution pH, contact time, initial CIP concentration, and different average oxidation states (AOS) of Mn in birnessite. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and molecular simulations were employed to investigate the adsorption mechanism of CIP on birnessite. Experimental results showed that surface adsorption instead of cation exchange was responsible for the uptake of CIP on birnessite. The quantum mechanics simulation showed that the final energy of the interaction between CIP and birnessite was smaller under the condition when the AOS of Mn was lower, in comparison to the case when the AOS of Mn was high. The highest CIP adsorption occurred under a weak alkaline condition.

Using probing compounds to investigate adsorption mechanism of ciprofloxacin on montmorillonite

Ciprofloxacin (CIP) adsorption on montmorillonite was investigated using structurally related probing compounds phenylpiperazine (PP) and fluorochloroquinolone carboxylic acid (FCQCA). Desorption of the equivalent amounts of exchangeable cations accompanying PP and CIP adsorption on montmorillonite suggested that cation exchange was the major adsorption mechanism for the CIP adsorption under acidic to neutral conditions, and the piperazine amine group was responsible for the cation exchange interaction. In contrast, the adsorption of CIP and FCQCA on montmorillonite indicated that hydrogen bonding between the keto carbonyl group and coordinated water in the interlayer of montmorillonite was mainly responsible for the CIP adsorption in alkaline aqueous solution as evidenced by Fourier transform infrared analyses. X-ray diffraction analyses demonstrated that both cation exchange and hydrogen bonding between the keto carbonyl group and coordinated water lead to the intercalation of CIP in montmorillonite.