Ciprofloxacin In Aqueous Solution Research Articles

Adsorption behavior of graphite‐like walnut shell biochar modified with ammonia for ciprofloxacin in aqueous solution

AbstractBACKGROUNDGraphite‐like biochar of NWSC600K was prepared at 900 °C using walnut shell as the raw material and aqueous ammonia (NH3·H2O) as an activator, and characterized using transmission and scanning eletron microscopy (TEM, SEM), X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy and Fourier transform infrared (FTIR). The study investigated the adsorption performance and mechanism of NWSC600K for ciprofloxacin (CIP).RESULTSThe results showed that extremely tiny pores were found on the surface of NWSC600K, which increased its specific surface area to 823.91 m2 g−1, whereas the average pore size of NWSC600K decreased to 3.23 nm. The results of TEM, XRD and Raman spectroscopy detected well‐arranged lattice stripes as well as characteristic peaks corresponding to the graphite lattice appearing on the surface of NWSC600K. Moreover, the ID/IG value for NWSC600K was 1.429. The FTIR results showed that functional groups including the amino group were formed on NWSC600K.CONCLUSIONThe adsorption capacity of NWSC600K for CIP was 158.14 mg g−1 and the corresponding removal rate was 97.5% at pH 7. The pH value impact on the removal efficiency of CIP greatly, and the removal rate of CIP decreased linearly with increasing pH. The coexisting ions also would inhibit the adsorption of CIP on NWSC600K. Results obtained from kinetic and isotherm models, thermodynamics and characterization analyses suggested that pore‐filling, π–π stacking, hydrogen bonding, hydrophobicity and electrostatic interaction existed during the adsorption process. The adsorption was a nonspontaneous exothermic reaction. © 2024 Society of Chemical Industry (SCI).

A novel adsorbent based electroplating sludge – rice husk char for removal of methylene blue and ciprofloxacin in aqueous solution

The adsorbent based electroplating sludge and rice husk char (CR) was prepared by ultrasonication method for adsorption of methylene blue (MB) and Ciprofloxacin (CIP) in water. The characteristics of adsorbent such as surface morphology, specific surface area, functional groups, element components was confirmed by SEM, BET, FT-IR, XRD and EDX. The results showed the adsorbent is porous structure with BET surface area of 175.22 m2/g, most of pore width belonged meso section. Removal effectiveness of MB and CIP were 99.89% and 74.96%, respectively after 90 min of adsorption. The experiment was implemented with the mockup model containing of methylene blue and ciprofloxacin in NH3.

Activation of persulfate by biochar-supported sulfidized nanoscale zero-valent iron for degradation of ciprofloxacin in aqueous solution: process optimization and degradation pathway.

The pollution of antibiotics, specifically ciprofloxacin (CIP), has emerged as a significant issue in the aquatic environment. Advanced oxidation processes (AOPs) are capable of achieving stable and efficient removal of antibiotics from wastewater. In this work, biochar-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC) was adopted to activate persulfate (PS) for the degradation of CIP. The impacts of different influencing factors such as S/Fe molar ratios, BC/S-nZVI mass ratios, PS concentration, S-nZVI/BC dosage, CIP concentration, initial pH, coexisting anions, and humic acid on CIP degradation efficiency were explored by batch experiments. The results demonstrated that the highest degradation ability of S-nZVI/BC was achieved when the S/Fe molar ratio was 0.07 and the BC/S-nZVI mass ratio was 1:1. Under the experimental conditions with 0.6 g/L S-nZVI/BC, 2 mmol/L PS, and 10 mg/L CIP, the degradation rate reached 97.45% after 90 min. The S-nZVI/BC + PS system showed significant degradation in the pH range from 3 to 9. The coexisting anions affected the CIP degradation efficiency in the following order: CO32- > NO3- > SO42- > Cl-. The radical quenching experiments and electron paramagnetic resonance (EPR) revealed that oxidative species, including SO4•-, HO•, •O2-, and 1O2, all contribute to the degradation of CIP, in which •O2- plays a particularly prominent role. Furthermore, the probable degradation pathway of CIP was explored according to the 12 degradation intermediates identified by LC-MS. This study provides a new idea for the activation method of PS and presents a new approach for the treatment of aqueous antibiotics with highly catalytic active nanomaterials.

Photocatalytic degradation of ciprofloxacin using a novel carbohydrate-based nanocomposite from aqueous solutions

Pharmaceutical substances in the ecosystem pose a notable hazard to human and aquatic organism well-being. The occurrence of ciprofloxacin (CIP) within water sources or the food chain can perturb plant biochemical processes and induce drug resistance in both humans and animals. Therefore, effective removal is imperative prior to environmental discharge. This study introduces a Novel Carbohydrate-Based Nanocomposite (Fe3O4/MOF/AmCs-Alg) as a proficient photocatalytic agent for degrading CIP in aqueous solutions. The fabricated nanocomposite underwent characterization using FTIR, XRD, FESEM, DRS, and VSM techniques. The analyses conducted verified the successful synthesis of the Fe3O4/MOF/AmCs-Alg nanocomposite. Utilizing the optimized parameters (pH = 5, nanocomposite dose = 0.4 g/L, CIP concentration = 10 mg/L, light intensity = 75 mW/cm2, and a duration of 45min), the Fe3O4/MOF/AmCs-Alg/Vis nanocomposite demonstrated an impressive CIP degradation efficiency of 95.85%. Under optimal experiment conditions, CIP removal efficiency in tap water and treated wastewater samples was 91.27% and 76.78%, respectively. Furthermore, the total organic carbon (TOC) analysis indicated a mineralization rate of 51.21% for CIP. Trapping studies demonstrated that the superoxide radical (O2°−) had a notable contribution to the breakdown of CIP. In summary, the Fe3O4/MOF/AmCs-Alg/Vis system offers numerous benefits, encompassing effective degradation capabilities, effortless catalyst retrieval, and remarkable nanocomposite reusability.

Green synthesis of CuO nanoparticles: A promising material for photocatalysis and electrochemical sensor

This research highlights the significant role of green synthesis in the production of copper oxide (CuO) nanoparticles by using natural extracts as reducing agents. These nanoparticles have shown promising potential in two key applications: photocatalytic degradation of industrial dye effluents and electrochemical sensing of ciprofloxacin. The study found that Arundinaria gigantea leaf extract is an effective reducing agent for synthesizing well-defined crystalline structure CuO nanoparticles, with an average size of 36 nm. The CuO nanoparticles have demonstrated high efficiency in photocatalytic applications, effectively degrading AR88 dye under UV irradiation, making them a viable solution for eco-friendly water purification. Additionally, when incorporated into an electrochemical sensor, these CuO nanoparticles have improved sensitivity and selectivity in detecting ciprofloxacin in aqueous solutions with high accuracy and precision. This study emphasizes the versatility and effectiveness of green-synthesized CuO nanoparticles for various practical uses.

Catalytic Degradation of Ciprofloxacin in Aqueous Solution by Peroxymonosulfate Activated with a Magnetic CuFe2O4@Biochar Composite

A magnetic copper ferrite and biochar composite (CuFe2O4@BC) catalyst was prepared by an improved sol-gel calcination method and initially used for the removal of antibiotics ciprofloxacin (CIP) by activated peroxymonosulfate (PMS). Using CuFe2O4@BC as the activator, 97.8% CIP removal efficiency could be achieved in 30 min. After a continuous degradation cycle, CuFe2O4@BC catalyst still exhibited great stability and repeatability and could also be quickly recovered by an external magnetic field. Meanwhile, the CuFe2O4@BC/PMS system presented good stability for metal ion leaching, which was far less than the leaching of metal ions in the CuFe2O4/PMS system. Moreover, the effects of various influencing factors, such as initial solution pH, activator loading, PMS dosage, reaction temperature, humic acid (HA), and the inorganic anions were explored. The quenching experiments and the electron paramagnetic resonance (EPR) analysis manifested that hydroxyl radical (•OH), sulfate radical (SO4•-), superoxide radical (O2•-), and singlet oxygen (1O2) were generated in the CuFe2O4@BC/PMS system, while 1O2 and O2•- are mainly involved in the degradation process. The synergistic effect between CuFe2O4 and BC enhanced the structural stability and electrical conductivity of the material, which promoted the bonding between the catalyst and PMS, resulting in the enhanced catalytic activity of CuFe2O4@BC. This indicates that CuFe2O4@BC activating PMS is a promising remediation technique for CIP-contaminated water.

Waste-Based Ceramsite for the Efficient Removal of Ciprofloxacin in Aqueous Solutions

Ciprofloxacin (CIP), a compound with bioaccumulation toxicity and antibiotic resistance, is frequently detected in water at alarming concentrations, which is becoming an increasing concern. In this study, a low-cost ceramsite was developed from industrial solid wastes through sintering to remove CIP from wastewater. The effects of adsorbent dosage, initial pH, contact time, initial CIP concentration, and temperature were explored. More than 99% of CIP (20-60 mg/L) was removed at around pH 2-4 by the ceramsite. The kinetic data fitted well with the pseudo-second-order model, revealing that chemisorption was the main rate-determining step. The isotherm data was better described by the Freundlich model, suggesting that CIP was removed by the formation of multiple layers on the heterogeneous surface. Moreover, the removal efficiency was practically higher than 95% during five regeneration cycles, when different regeneration methods were used, including calcination, HCl, and NaOH washing, indicating that the ceramsite exhibited outstanding reusability in removing CIP. The primary mechanism of CIP removal by the ceramsite was found to be the synergism of adsorption and flocculation, both of which depended on the release of Ca2+ from the ceramsite. In addition, strong Ca-CIP complexes could be formed through surface complexation and metal cation bridging between Ca2+ and different functional groups in CIP.

Evaluation of Sono-photocatalytic Removal of Ciprofloxacin Antibiotic Using Magnesium Oxide Nanoparticles from Aqueous Solutions

Objectives: The entry of antibiotics into surface and groundwater will cause problems in the environment. This study aimed to investigate the removal efficiency of ciprofloxacin (CFX) from aqueous solutions using the sonophotocatalytic process of Magnesium Oxide Nanoparticles (MgO). Materials and Methods: This study is an experimental-laboratory study performed in a reactor with a discontinuous system. In this study, the effect of parameters such as solution pH, MgO dose, reaction time in two processes, photocatalyst and sonocatalyst, initial concentration of antibiotic and the power of UV lamps in the photocatalytic reactor at ultrasonic frequencies of 35 and 130 kHz on the reduction of CFX in aqueous solution was investigated. Results: The results showed that the process of photosonocatalysis with MgO can effectively lead to the removal of the antibiotic CFX. In the process of using a photosonocatalyst with a pH of 7 and ultrasonic waves with a frequency of 35 kHz and an optimal time of 30 min, 0.3 g/L of MgO, CFX concentration of 150 mg/l, UV lamp with a power of 30 watts and the optimal irradiation time of 60 min was obtained as the optimal variables in the removal of CFX antibiotic. Conclusion: The results showed that the photosonocatalytic process with the help of MgO is an effective and efficient method to remove the CFX antibiotic from aqueous solutions.

Enhanced Visible-Light-Responsive Photocatalytic Degradation of Ciprofloxacin by the CuxO/Metal-Organic Framework Hybrid Nanocomposite.

Ciprofloxacin (CIP) is a commonly used antibiotic, however, once in the environment, it is highly toxic with a poor biodegradability. Given these attributes, an effective strategy for the removal of CIP is urgently needed for the protection of water resources. Herein, a novel copper metal-organic framework (CuxO/MOF) multifunctional material has been produced, in this work, by the calcination of Cu-MOF urea at 300 °C, in the presence of a 5% H2 atmosphere. The morphological, structural, and thermal properties of the prepared CuxO/MOF were determined through various techniques, and its photocatalytic behavior was investigated for the degradation of CIP under visible-light irradiation. The prepared CuxO/MOF bifunctional material is presented as a graphitic carbon-layered structure with a particle size of 9.2 ± 2.1 nm. The existence of CuO-Cu2O-C, which was found on the CuxO/MOF surface, enhanced the adsorption efficiency and increased the photosensitivity of CuxO/MOF, towards the degradation of CIP in aqueous solutions. The tailored CuxO/MOF, not only shows an excellent CIP degradation efficiency of up to 92% with a constant kinetic rate (kobs) of 0.048 min−1 under visible light, but it can also retain the stable photodegradation efficiency of >85%, for at least six cycles. In addition, CuxO/MOF has an excellent adsorption capacity at pH 6.0 of the maximum Langmuir adsorption capacity of 34.5 mg g−1 for CIP. The results obtained in this study demonstrate that CuxO/MOF is a reliable integrated material and serves as an adsorbent and photocatalyst, which can open a new pathway for the preparation of visible-light-responsive photocatalysts, for the removal of antibiotics and other emerging pollutants.

Adsorption study on the removal of ciprofloxacin in aqueous solution by an acidic ion exchange resin with bifunctional group

Removal of fluoroquinolone antibiotic pollutants in the aquatic environment has become a research hotspot. In this work, two skeletal resins and four acidic ion exchange resins have been used as adsorbent materials to evaluate their adsorption properties for fluoroquinolone antibiotic ciprofloxacin (CIP) in aqueous solution. Compared with other materials, the sulfonic-phosphoric acid-based bifunctional resin S9570 has shown the best adsorption performance for CIP. The effect of solution pH on the adsorption of CIP by S9570 has been further explored, and the optimal adsorption capacity has been obtained at pH 4.0. The adsorption kinetics and thermodynamics of S9570 for CIP have been investigated in details. The high fits of the pseudo-second-order and intraparticle diffusion equations indicate that these two models can better describe the adsorption process of S9570 for CIP which has been jointly controlled by chemical adsorption and intraparticle diffusion steps and has been accompanied by weak or intermediate initial adsorption behaviour. The best fit results of Langmuir has indicated that there exists a monolayer adsorption on the surface of the S9570.Thermodynamic parameters suggest that the adsorption is an endothermic, spontaneous process with increased randomness at the solid-liquid interface. Through this evaluation of resin adsorption materials, it has been proved that the adsorbent material has good reusability and antiinterference performance.

Perovskites in photoelectrocatalytic water treatment: Bismuth ferrite - graphite nanoparticles composite photoanode for the removal of ciprofloxacin in water

Towards the application of perovskite in photoelectrocatalytic oxidation of organic pollutants in water, bismuth ferrite (BiFeO3) was prepared by facile hydrothermal method and composited with graphite nanoparticles (GNPs) to form BiFeO3/GNPs composite. The photoanodes of BiFeO3, GNPs and BiFeO3/GNPs were fabricated on a fluorine doped tin oxide (FTO) glass substrate. The materials and photoanodes were characterised with X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectroscopy (UV-DRS). Furthermore, the photoanodes were photoelectrochemically characterised by evaluating their photocurrent response and charge transfer resistance with impedance spectroscopy. Results confirmed that the visible light absorbance of BiFeO3 was enhanced by the addition of GNPs. The BiFeO3/GNPs showed marked enhancement in the photocurrent density and low charge transfer resistance over BiFeO3 owing to the excellent electrical conductivity of graphite nanoparticle. The photoelectrocatalytic performance of BiFeO3, GNPs and BiFeO3/GNPs photoanodes were studied through the degradation of ciprofloxacin in aqueous solution. Degradation percentages of 48 %, 50 % and 78 % were recorded for BiFeO3, GNPs and BiFeO3/GNPs after 4 h respectively. In addition, the total organic carbon (TOC) removal analysis showed 30 %, 38 % and 56 % for BiFeO3, GNPs and BiFeO3/GNPs respectively. The study showed the beneficial effect of doping BiFeO3 with graphite nanoparticles and also the synergy of electrochemical oxidation and photocatalysis in photoelectrocatalytic process performance. Degradation pattern and product studies, obtained from ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS) and scavenger studies data, showed that the degradation of ciprofloxacin was activated by the hydroxyl and hole radicals and it followed a direct oxidation of piperazine ring with other intermediate degradation products. The composite photoanode exhibited good stability and reusability.

Degradation of ciprofloxacin in aqueous solution using ozone microbubbles: spectroscopic, kinetics, and antibacterial analysis

Ciprofloxacin (CIP) has been listed in the last version of the surface water due to its ability to kill human cells by inhibiting the activity of DNA topoisomerase IV. Thus, CIP, along with other antibiotic pollution has become a serious threat to the environment and public health. Ozonation has been used as an advanced technique that is applied in wastewater treatment to remove CIP, but the primary limitation of this method is the low solubility of ozone in water. This study is the first report of CIP removal in a scale-up of its aqueous solution using a self-developed aerator pump-enhanced ozonation (APO) system, which only employs a propeller and a zigzag arrangement of meshes. This aerator pump decreased the size of ozone bubbles by 90% and increased the effective ozone solubility to 0.47 ppm. The mechanism of degradation of CIP is attributed to an oxidation reaction of the antibiotic with reactive oxygen species, such as hydroxyl, oxygen, and hydroperoxyl radicals, generated on the surface of the ozone microbubbles. It was found that the rate and efficiency of degradation of CIP using the APO system were 3.64 × 10−3/min and 83.5%, respectively, which is higher compared with those of conventional flow ozonation (FO) systems (1.47 × 10−3/min and 60.9%). The higher degradation efficiency of CIP by the APO system was also revealed by its higher electrical energy efficiency (0.146 g/kWh), compared to that of the FO system (0.106 g/kWh). The degradation of CIP was also monitored by the resulting antibacterial activity against Escherichia coli and Staphylococcus aureus.

Solar Light-Assisted Oxidative Degradation of Ciprofloxacin in Aqueous Solution by Iron(III) Chelated Cross-Linked Chitosan Immobilized on a Glass Plate

The massive worldwide use of antibiotics leads to water pollution and increasing microbial resistance. Hence, the removal of antibiotic residues is a key issue in water remediation. Here, we report the solar light-assisted oxidative degradation of ciprofloxacin (CPF), using H2O2 in aqueous solution, catalyzed by iron(III) chelated cross-linked chitosan (FeIII-CS-GLA) immobilized on a glass plate. The FeIII-CS-GLA catalyst was characterized by FTIR and 57Fe-Mössbauer spectroscopies as well as X-ray diffraction, revealing key structural motifs and a high-spin ferric character of the metal. Catalytic degradation of CPF was investigated as a function of solar light irradiation time, solution pH, concentration of H2O2 and CPF, as well as cross-linker dosage and iron(III) content in FeIII-CS-GLA. The system was found to serve as an efficient catalyst with maximum CPF degradation at pH 3. The specific ·OH scavenger mannitol significantly reduces the degradation rate, indicating that hydroxyl radicals play a key role. The mechanism of catalytic CPF degradation was evaluated in terms of pseudo-first-order and Langmuir-Hinshelwood kinetic models; adsorption of CPF onto the FeIII-CS-GLA surface was evidenced by field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. FeIII-CS-GLA can be reused multiple times with only minor loss of catalytic efficiency. Antimicrobial activity tests performed against both Gram-negative (Escherichia coli DH5α, Salmonella typhi AF4500) and Gram-positive bacteria (Bacillus subtilis RBW) before and after treatment confirmed complete degradation of CPF. These results establish the immobilized FeIII-CS-GLA as a rugged catalyst system for efficient photo-Fenton type degradation of antibiotics in aqueous solutions.

Degradation of Ciprofloxacin in Aqueous Solution Using Ozone Microbubbles: Spectroscopic, Kinetics, and Antibacterial Analysis

Degradation of Ciprofloxacin in Aqueous Solution Using Ozone Microbubbles: Spectroscopic, Kinetics, and Antibacterial Analysis

Synthesis of S doped TiO2 (S-TiO2) to enhance photocatalytic degradation of Ciprofloxacin in aqueous solutions under visible light

In this study, the sol-gel method was successfully used to synthesize S-TiO2 for efficient photocatalytic degradation of Ciprofloxacin solution under visible irradiation. These synthesized materials were characterized by various analytical methods such as XRD, SEM-EDX, FT-IR, and UV diffuse reflectance spectroscopy (DRS). XRD, SEM-EDX, and FT-IR confirmed the successful preparation of these materials. The UV-DSR demonstrated that the material has a lower bandgap in comparison with prime TiO2. The photodegradation results reported that the 0.33S-TiO2 had shown high efficiency in the degradation of Ciprofloxacin in comparison with TiO2. The decomposition of 10 mg/L Ciprofloxacin concentration reached approximately 90% for 150 minutes of visible light irradiation at room temperature at pH = 4.

Synergetic Effect of Dual Functional Monomers in Molecularly Imprinted Polymer Preparation for Selective Solid Phase Extraction of Ciprofloxacin.

Background: Ciprofloxacin (CIP), an important broad-spectrum fluoroquinolone antibiotic, was often used as a template molecule for the preparation of imprinted materials. In this study, methacrylic acid and 2-vinylpyridine were employed for the first time as dual functional monomers for synthesizing ciprofloxacin imprinted polymers. Methods: The chemical and physicochemical properties of synthesized polymers were characterized using Fourier transform-infrared spectroscopy, thermogravimetric analysis-differential scanning calorimetry, scanning electron microscopy, and nitrogen adsorption-desorption isotherm. The adsorption properties of ciprofloxacin onto synthesized polymers were determined by batch experiments. The extraction performances were studied using the solid phase extraction and HPLC-UV method. Results: The molecularly imprinted polymer synthesized with dual functional monomers showed a higher adsorption capacity and selectivity toward the template molecule. The adsorbed amounts of ciprofloxacin onto the imprinted and non-imprinted polymer were 2.40 and 1.45 mg g−1, respectively. Furthermore, the imprinted polymers were employed as a selective adsorbent for the solid phase extraction of ciprofloxacin in aqueous solutions with the recovery of 105% and relative standard deviation of 7.9%. This work provides an alternative approach for designing a new adsorbent with high adsorption capacity and good extraction performance for highly polar template molecules.

Hypoxanthine Modified Polyethylene Glycol Diglycidyl Ether Gel for Ciprofloxacin Adsorption

A hypoxanthine modified polyethylene glycol diglycidyl ether gel was prepared by the ring opening polymerization of polyethylene glycol diglycidyl ether with hypoxanthine in a simple sol-gel method. The structure and composition were characterized by SEM, FT-IR, BET and XRD. The adsorption experiments of ciprofloxacin at different pH, temperature, contact time and initial concentration were studied. The results show that the gel is porous with the average pore size of 5.2 nm, the optimum adsorption pH is 5 and the saturated adsorption time is 240 minutes. The maximum equilibrium adsorption capacity of ciprofloxacin is 56.1 mg/g at 308 K according to the Langmuir model. The repeated adsorption experiments show that the gel could still adsorb 80% of the first adsorbed ciprofloxacin after 5 times of elution. These results indicate that the gel can be used as a practical adsorbent for ciprofloxacin in aqueous solution.

In-situ dual effect of Ag-Fe-TiO2 composite for the photocatalytic degradation of Ciprofloxacin in aqueous solution

Industrial waste materials such as Fly Ash (FA), Foundry Sand (FS) were used as support material by mixing them with clay to fix the catalyst. Where FA and FS served as an iron (Fe) source to induce the photo-Fenton process. The presence of Fe in FA and FS was affirmed by SEM-EDS characterization. UV-DRS was performed to analyze the bandgap of the composite which reduced from 2.96 to 2.82 eV after doping TiO2 with Ag. This composite was used to initiate photocatalysis. The fixing of catalyst on a support formed the Fe-Ag-TiO2 complex which led to the commencement of the in-situ dual process(i.e. photocatalysis and photo-Fenton) in fixed bed mode. After the optimization of several parameters such as H2O2 dose, the area covered by beads, A/V ratio, Flow rate, pH under solar irradiations for 60 min, 94.4% degradation of CIP was attained. XRD analysis was carried out to confirm the crystallographic phases of the composite anatase and rutile phases of TiO2 were present in the composite. The systematic leaching of iron took place in this process and was confirmed by iron estimation during the reaction process. To understand the elemental composition of the composite SEM-EDS was performed and the present of TiO2, Fe and Ag was affirmed. Composite beads were stable and active even after the 30 recycles as confirmed by SEM-EDS. The intermediate products were analyzed by GC-MS analysis whereas the toxicity of the treated samples was studied by the zone inhibition test.

Removal of Ciprofloxacin from Aqueous Solution Using Prepared Biodegradable Potato Cross-linked Starch Ester

Potato starch was modified chemically to prepare an adsorbent that is efficient for removing the ciprofloxacin antibiotic from its aqueous solution. The chemical modification process of potato starch involved cross-linking and esterification steps. The high-resolution X-ray diffraction characterization shows that the modification processes do not damage the starch crystal but reduces the crystallinity and the crystal size. In addition to that, holes on the surface of the round and oval shapes of the modified starch were noticed via scanning electron microscope. The parameters that could affect ciprofloxacin removal efficiency on cross-linked potato starch ester were investigated in detail, which included initial concentration of ciprofloxacin in aqueous solution, pH and temperature. The removal efficiency of ciprofloxacin increased with the increase in the initial pH value of the aqueous solution and reached the highest value of removal at a pH of 7, after which it was noticed that the removal efficiency decreased. The removal efficiency was decreased with increasing initial concentration of ciprofloxacin (expressed as chemical oxygen demand) from 25 to 125 ppm. Finally, the results showed that the increase in the temperature treatment from 25 to 45 °C negatively affected the removal efficiency.

Chemical speciation of ciprofloxacin in aqueous solution regulates its phytotoxicity and uptake by rice (Oryza sativa L.)

Ciprofloxacin (CIP), a widely used fluoroquinolone antibiotic, is frequently detected in aqueous environments, and could be assimilated by vegetable plants to possess potential threats to human and animal health through food chains. However, plant uptake of CIP in different chemical speciation has still far from clear now. Thus, the toxicity and uptake of CIP by rice plants were investigated under different solution pH, owing to its contribution to different chemical speciation of CIP. Results display that high pH-driven changes of CIP from cation (CIP+) to anion (CIP−) decreased its adsorption and uptake by excised roots and intact plants, respectively. However, CIP concentrations in roots, stems and leaves all exhibited no significant differences with increasing solution pH. Moreover, six intermediates of CIP were detected and two possible transformation pathways were proposed in rice plants, including firstly oxidation and following consecutive cleavage of piperazine ring. After accumulated in plant tissues, CIP significantly inhibited the plant growth, decreased the photosynthetic pigments contents and enhanced the antioxidant enzyme activities in a concentration-dependent manner. Besides, high pH exacerbated the growth inhibition and changed the oxidative damage responses of rice plants to CIP. These findings indicate that the uptake and toxicity of CIP in rice plants were influenced by solution pH-driven changes of its chemical speciation.