Degradation Pathways Of Ciprofloxacin Research Articles

Photocatalytic application towards the degradation of ciprofloxacin and algae by Z-scheme 2D/3D heterojunction of Bi12O17Cl2/UiO-66-NH2

With the continuous emergence of antibiotics in natural water bodies, the crisis of water environment is becoming increasingly serious. To efficiently remove antibiotics, a novel 2D/3D Z-scheme heterojunction of Bi12O17Cl2/UiO-66-NH2 was constructed by in situ growth technology. The formation of Z-scheme heterojunction between Bi12O17Cl2 and UiO-66-NH2 not only significantly improves the transfer rate and separation efficiency of charge carriers, but also greatly prolongs the lifetime of electrons and improves their light absorption ability. Free radical capture experiments and ESR spectra display that ⋅O2− and ⋅OH radicals dominate the degradation process of ciprofloxacin. The synthesized Z-scheme heterojunction shows a high degradation rate of 83.5 % for antibiotic ciprofloxacin within 60 min, much higher than those of Bi12O17Cl2, UiO-66-NH2 monomers and many other reported photocatalysts. The heterojunction Bi12O17Cl2/UiO-66-NH2 also exhibits excellent degrading performance towards antibiotics in three actual water bodies (tap water, lake water and the effluent of domestic sewage treatment plant). Meanwhile, the as-prepared photocatalyst can effectively degrade Microcystis aeruginosa and algal toxin Microcystin-LR in surface water bodies contaminated by algae and antibiotics. The QSAR analysis indicates that the toxicities of both ciprofloxacin and its intermediates are greatly reduced. The degradation pathways of ciprofloxacin were analyzed via Density Functional Theory calculations and QSAR analysis. This study provides an excellent synthesis method of Z-scheme heterojunction for the purification of surface water bodies contaminated by algae and antibiotics via photocatalytic technology.

Hollow α-Bi2O3/TiO2 nanotube arrays hierarchical heterojunction with strong interface interaction for efficient photocatalytic ciprofloxacin degradation

Interfacial regulation for photocatalyst is considered as an effective strategy to enhance visible-light utilization and charges transfer. But it is still a great challenge for the conscious design of interfacial engineering. Herein, hollow α-Bi2O3/TiO2 nanotube arrays (α-Bi2O3/TNAs) hierarchical heterojunction was constructed to modulate the interface structure for efficient photocatalytic degradation of ciprofloxacin (CIP). The systematic characterization analysis, density functional theory (DFT) calculations and electron paramagnetic resonance spectra revealed that the Z-scheme charges transfer mechanism was affirmed between α-Bi2O3 and TNAs. The hierarchical tubular heterostructure was contributed to enhancing light absorption, and the strong interfacial interaction could promote the separation and transfer of photogenerated charges. The optimal α-Bi2O3/TNAs exhibited higher photocatalytic activity for CIP (73.9 %) than TNAs (25.3 %) under visible-light irradiation. The anions and natural organic matters could decline CIP removal owing to competing active sites or aggravating radicals consumption. The theoretical calculations further demonstrated that the staggered energy levels produced an internal electric field at heterojunction interface to promote charges transfer. Three degradation pathways of CIP were proposed based on DFT calculations and LC-MS. The photocatalytic degradation of CIP by α-Bi2O3/TNAs could effectively reduce its toxicity, and eventually alleviate the environmental hazards of antibiotics.

Three-dimensional electrochemical Fenton degradation of CIP by doping Ce and Cu in Jacaranda shell base as particle electrodes

Currently, ciprofloxacin (CIP) in water environments has attracted wide attention. In order to degrade CIP by electrocatalysis, it is very important to develop catalysts with high catalytic activity as particle electrodes. In this study, Jacaranda shell was made into biochar (BC) by calcination, Ce and Cu modified BC (Ce-Cu/BC) was prepared by a simple impregnation and calcination method as a particle electrode in a three-dimensional electro-Fenton (3D/EF) system to degrade CIP. Characterization of the Ce-Cu/BC particle electrodes was conducted using SEM, XRD, and XPS, revealing the porous structure of the calcined jacaranda shell base, confirming successful loading of Ce and Cu. Optimal operating conditions for CIP removal were determined to be 4 g/100 mL particle electrodes dosage, initial pH of 5, 8 V voltage, and 2 mM Fe2+ concentration, resulting in a maximum CIP removal rate of 84.97% with an energy consumption of 1.32 W•h. Stability tests demonstrated the robustness of Ce-Cu/BC, while comparative tests and radical extinction experiments highlighted the high electrocatalytic activity of the 3D/EF system, primarily attributed to the indirect oxidation of •OH, an active substance generated within the system LC-MS and UV full-band scanning analyses were employed to propose potential CIP degradation pathways.

Cobalt nanoparticles embedded in carbon nanotubes with high specific surface area activate peroxymonosulfate to degrade ciprofloxacin

Advanced oxidation method based on sulfate radical (SO4−) are increasingly used to degrade organic pollutants. However, high-efficient and stable catalysts are still needed at this stage. In this study, nitrogen-doped carbon nanotubes coated cobalt nanoparticles (Co@NCNTs) were prepared by a simple and rapid pyrolysis method and employed as a high performance peroxymonosulfate (PMS) activator for degradation of the antibiotic ciprofloxacin (CIP). The Co@NCNTs/PMS system achieved 100 % removal of CIP in 40 min with low metal leaching. The effects of Co@NCNTs on PMS activation under different experimental conditions were investigated. The catalyst maintained excellent catalytic activity in the presence of different anions and humic acids and in a wide pH range (4–9). SO4– was identified as the active substance primarily responsible for removing CIP. The possible degradation pathway of CIP was proposed by analyzing the degradation intermediates of CIP. This work provides a high-performance catalyst to activate PMS for the removal of antibiotic with low metal leaching.

Edge interface microenvironment regulation of CoOOH/commercial activated carbon nano-hybrids enabling PMS activation for degrading ciprofloxacin

Peroxymonosulfate (PMS) is widely employed to generate oxygen-containing reactive species for ciprofloxacin (CIP) degradation. Herein, cobalt oxyhydroxide @activated carbon (CoOOH@AC) was synthesized via a wet chemical sedimentation method to activate PMS for degradation of CIP. The result suggested AC can support the vertical growth of CoOOH nanosheets to expose high-activity Co-contained edges, possessing efficient PMS activation and degradation activity and catalytic stability. In the presence of 3.0 mg of optimal CoOOH@AC and 2 mM PMS, 96.8 % of CIP was degraded within 10 min, approximately 11.6 and 9.97 times greater than those of CoOOH/PMS and AC/PMS systems. Notably, it was disclosed that the optimal CoOOH@AC/PMS system still exhibited efficient catalytic performance in a wide pH range, different organics and common co-existing ions. Quenching experiments and electron paramagnetic resonance indicated that both radical and non-radical processes contributed to the degradation of CIP, with 1O2 and direct electron transfer accounting for the non-radical pathway and SO4•− and •OH serving as the main radical active species. Finally, possible CIP degradation pathways were proposed based on high-performance liquid chromatography-mass spectrometry. This study provided an alternate method for wastewater treatment based on PMS catalyzed by cobalt-based hydroxide.

Physiological responses and removal mechanisms of ciprofloxacin in freshwater microalgae

Antibiotics, such as ciprofloxacin (CIP), are frequently detected in various environmental compartments, posing significant risks to ecosystems and human health. In this study, the physiological responses and elimination mechanisms of CIP in Chlorella sorokiniana and Scenedesmus dimorphus were determined. The exposure CIP had a minimal impact on the growth of microalgae, with maximum inhibit efficiency (IR) of 5.14% and 22.74 for C. sorokiniana and S. dimorphus, respectively. Notably, the photorespiration in S. dimorphus were enhanced. Both microalgae exhibited efficient CIP removal, predominantly through bioaccumulation and biodegradation processes. Intermediates involved in photolysis and biodegradation were analyzed through Liquid Chromatography High Resolution Mass Spectrometer (HPLC-MS/MS), providing insights into degradation pathways of CIP. Upregulation of key enzymes, such as dioxygenase, oxygenase and cytochrome P450, indicated their involvement in the biodegradation of CIP. These findings enhance our understanding of the physiological responses, removal mechanisms, and pathways of CIP in microalgae, facilitating the advancement of microalgae-based wastewater treatment approaches, particularly in antibiotic-contaminated environments.

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.

Energy-saving piezoelectric pipe functionalized by C3N5/polyvinylidene fluoride composites for enhanced degradation of ciprofloxacin

Piezocatalytic technology has been widely used for pollutant degradation, but usually suffers from high energy consumption and secondary pollution. To address these shortcomings, we constructed a green energy-saving piezoelectric pipe functionalized by C3N5/polyvinylidene fluoride composites for pollutant degradation. The synergistic effect of C3N5 and polyvinylidene fluoride profoundly improved the piezoelectric attributes of the composites and accelerated the carrier separation efficiency within materials. Under flowing water, the piping device showcased an exceptional ciprofloxacin removal rate of 93 % in 40 min and maintained excellent degradation performance after multiple cycles. Notably, the energy consumption in the whole process was only 82.64 kWh m−3 order-1. Three main possible degradation pathways of ciprofloxacin were suggested based on LC-MS results and frontier orbit theory calculations. Toxicity analysis further confirmed the reduction of ciprofloxacin ecotoxicity after degradation. The pipe system also displayed good universality and recyclability, providing new insights for environmental remediation.

A novel strategy for efficient utilization of carbon residue from biomass gasification loaded NiCo2O4 to construct composite catalysts for activation of peroxymonosulfate to effectively remove antibiotics

Carbon residue (CR) derived from biomass gasification is a type of solid waste discharged from the biomass gasifier. CR is a carbon-rich material with a large specific surface area. Herein, NiCo2O4 nanoparticles were generated in situ on CR via a facile solvothermal method and the NiCo2O4-CR (NCCR) composite catalysts were prepared via solvothermal synthesis followed calcination method. The catalytic activity of NCCR was investigated by activating peroxymonosulfate (PMS) for the ciprofloxacin (CIP) degradation. The NCCR/PMS system exhibited the degradation efficiency, TOC removal efficiency, and removal reaction rate constant (k) of 93.86 %, 44.09 %, and 0.049 min−1 for CIP in 60 min, respectively, which were 1.17, 1.21 and 1.20 times of those in the NiCo2O4/PMS system, suggesting that CR had a positive impact on the improvement of the catalytic properties of NiCo2O4. Significantly, NCCR showed remarkable performance in terms of pH adaptation range, resistance to environmental disturbances, reusability, and other contamination applications. SO4•–, O2•– and 1O2，as the dominant reactive oxygen species, disrupt the molecular structure of CIP. PMS activation with NCCR mainly form free radicals and non-free radicals catalyzed by the redox couples of Co (III)/Co (II) and Ni (III)/Ni (II). Specially, Co (IV) = O also form and participate in the CIP degradation via a non-free radical pathway. Three possible degradation pathways of CIP were suggested by the degradation intermediates. The CIP degradation in the NCCR/PMS system was a process of reducing toxicity, protecting water ecosystem. The study provides a method to improve the catalytic properties of transition metal for activating PMS to purify antibiotic contamination wastewater, and opens a novel insight to deal with the solid waste from biomass gasification.

Magnetically recoverable Ni-doped iron oxide/graphitic carbon nitride nanocomposites for the improved photocatalytic degradation of ciprofloxacin: Investigation of degradation pathways

Developing efficient and effective photocatalysts is essential for organic dyes and antibiotic degradation in wastewater. Ni-doped α-Fe2O3/g-C3N4 (NFGCN) photocatalysts were synthesised through a simple co-precipitation technique and used for the ciprofloxacin (CIP) and methylene blue (MB) degradation through photocatalysis. The XRD data indicated the crystallinity of the synthesised iron oxide and its composites with rhombohedral structures with the nature of high purity. The morphology of the NFGCN composite revealed the construction of Ni-doped α-Fe2O3 (NFO) nanoparticles onto the g-C3N4 (GCN) sheet surface along with the close interface that induced a Z-scheme heterojunction. The synthesised photocatalysts showed photocatalytic activity with good degradation efficiency of 82.1 % and 92.0 % for CIP and MB, respectively, within 120 min under solar light exposure. The improved photocatalytic degradation efficiency was attained owing to the synthesised composite's enhanced light absorption in the visible range. The narrow band gap energies and interaction between Ni-doped α-Fe2O3 and g-C3N4 displayed by these materials result in enhanced visible light absorption, effective charge carrier separation and transportation to the pollutants. CIP degradation pathways were investigated utilising the LC-MS analysis. NFGCN composites showed good recyclability (5 cycles), magnetic retrievability, and stability for degrading organic and emerging pollutants from wastewater through photocatalysis.

Waste-derived MCM-41 as dual-functional support for cobalt ferrite: Performance as peroxymonosulfate activator for ciprofloxacin decontamination

Herein, a series of CoFe2O4 decorated on waste-derived Mobil Composition of Matter No. 41 (MCM-41) was developed. Incorporation of MCM-41 as a support for CoFe2O4 (CFMCM) provides dual functionality to disperse the catalyst and adsorb leached metal, leading to remarkable performance and stability. The CFMCM was used as a peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal indicating that CFMCM with 11 wt% CoFe2O4 (CFMCM-11) had the highest performance (kapp = 0.17 min−1). Increasing the catalyst loading and PMS dosage contributed positively to the CIP degradation. The catalyst can be reused at least 3 times without significant metal leaching (<35 µg/L) showing that it is stable. Analysis of the dominant reactive species using scavengers revealed that SO4•− was the major reactive species while HO• played a minor role. The SO4•− and HO• were generated from the redox transition between Co2+/Co3+ and Fe2+/Fe3+. Based on the intermediates identified, the CIP degradation pathways consisting of piperazine ring oxidation, and decarboxylation reactions were proposed. Overall, this study shows that the waste-derived materials can be integrated as part of the strategy to develop catalysts for environmental applications.

Ultra-fast degradation of ciprofloxacin by the peroxymonosulfate activation using a Co/Al-LDH decorated magnetic hydrochar: Structural design, catalytic performance and synergistic effects

CoFe2O4/BHC-LDH3 catalyst was constructed by decoration of Co/Al layered double hydroxides (Co/Al-LDH) on bamboo hydrochar (BHC) loaded with magnetic CoFe2O4 to activate peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation. Taking advantage of structural modulation and synergistic effects between the multi-components, CoFe2O4/BHC-LDH3 demonstrated high efficient PMS activation and ultra-fast CIP removal (91.50 % within 10 min), compared with BHC (6.26 %), CoFe2O4 (26.32 %), and Co/Al-LDH (40.10 %). Both free radical (SO4–) and non-radical (1O2) were crucial during the degradation process, and a substantial decrease in aquatic toxicity of the intermediates was observed. Additionally, the stability of CoFe2O4/BHC-LDH3 in actual water environment was tested using a fixed-bed reactor, illustrating the CoFe2O4/BHC-LDH3 has good stability and anti-interference ability in long-term operation. Possible degradation pathways of CIP in the CoFe2O4/BHC-LDH3 + PMS system were proposed based on liquid chromatography-mass spectrometer analysis and density functional theory calculation. This work provides new strategies for hydrochar-supported catalyst synthesis for organic pollutants decomposition.

Optimization of Visible-Light-Driven Ciprofloxacin Degradation Using a Z-Scheme Semiconductor MgFe2O4/UiO-67.

A heterogeneous photocatalyst, MgFe2O4/UiO-67 (MU-x), was successfully synthesized by doping magnetic magnesium ferrite nanoparticles (MgFe2O4) with the UiO-67 metal-organic framework at various weight ratios (MgFe2O4: UiO-67 at 30, 50, 70, and 90 wt %). Various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) , Brunauer-Emmett-Teller (BET), photoluminescence (PL), vibrating sample magnetometry (VSM), electrochemical impedance spectroscopy (EIS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), were used to characterize the prepared photocatalysts. The photocatalytic performance of MU-x in the degradation of ciprofloxacin (CIP) under visible light was assessed. The CIP degradation efficiency was found to increase as the amount of MgFe2O4 in the composite was increased up to 70 wt %. Experimental conditions were optimized using response surface methodology (RSM) based on central composite design (CCD) with three factors: initial pH, catalyst loading, and CIP concentration. Using the obtained model, the optimal conditions were determined as follows: initial pH of 8.025, catalyst loading of 33.8 wt %, and CIP concentration of 10.8 mg/L. Under these optimal conditions, a notable improvement was achieved, with 99.62% of CIP removal achieved within 90 min, surpassing the performance of previously reported photocatalysts. Total organic carbon (TOC) analysis revealed a high degree of mineralization, at 81.25%. The degradation pathway of CIP was investigated based on liquid chromatography-mass spectrometry (LC-MS) analysis. Finally, the values of ECB and EVB of the photocatalyst were determined and the possible degradation mechanism of CIP was investigated based on Mott-Schottky and the applied scavengers. The hydroxyl radical (•OH) was identified as the dominant species in the removal of CIP through a trapping experiment. The photocatalyst with 70 wt % of MgFe2O4 (MU-70) exhibited excellent stability and recoverability with an external magnet, demonstrating 86.33% CIP removal after four cycles. According to the obtained results, MU-70 is a promising visible-light-active photocatalyst with great potential for water treatment applications and convenient recovery.

Construction of surface plasmonic Bi nanoparticles and α-Bi2O3 co-modified TiO2 nanotube arrays for enhanced photocatalytic degradation of ciprofloxacin: Performance, DFT calculation and mechanism

The heterogeneous photocatalysis was considered as a sustainable and environmentally friendly technology to rapidly eliminate organic contaminants in water, but its practical application was severely limited by difficult recyclability, low visible-light utilization and high carriers recombination of traditional photocatalysts. Herein, the surface plasmonic Bi nanoparticles and α-Bi2O3 co-modified TiO2 nanotube arrays (Bi/Bi2O3/TNAs) were optimally prepared in situ on titanium foils. The interface interaction among TNAs, α-Bi2O3 and Bi nanoparticles demonstrated the successful construction of tight ternary heterojunction. Bi/Bi2O3/TNAs effectively solved the recovery of traditional photocatalysts, and exhibited more excellent photocatalytic activity (90.3%) to ciprofloxacin (CIP) than TNAs (25.3 %). The enhancing photocatalytic activity was associated with the improved visible-light utilization and suppressed carriers recombination. The coexistence of inorganic anions and natural organic matters declined CIP removal owing to competing active sites or quenching radicals. The density functional theory calculations further demonstrated that the staggered energy levels caused the generation of an internal electric field at the heterojunction interface, which promoted charges transfer. Two main degradation pathways of CIP were proposed, and Bi/Bi2O3/TNAs photocatalytic system could realize the gradually detoxification of CIP.

Highly effective and recyclable ZnCo2O4@NF for peroxymonosulfate activation towards ciprofloxacin degradation: Dual reaction sites and enhanced electron transfer mechanisms

The nano/micro-sized catalysts for peroxymonosulfate (PMS) activation often undergo agglomeration, leading to inevitable loss of active sits and reduced catalytic efficiency. Herein, monolith nickel foam (NF) supported ZnCo2O4 nanosheets were constructed, achieving almost complete removal of ciprofloxacin (CIP) within 15 min. ZnCo2O4@NF exhibits prominent stability in microstructure and exposed active sites, resulting in high reusability. The unique Zn-O-Co structure and “conducting bridge” of NF could accelerate the electron transfer from ZnCo2O4 to PMS and the following O-O bond cleavage. This facilitates Co2+/Co3+ redox cycle for continuous SO4•− generation and endows ZnCo2O4@NF with low reaction barrier. The surface hydroxyl groups and the inner-sphere complexation between PMS and catalyst play significant role in the formation of reactive oxygen species (ROS). Furthermore, the quenching test confirmed the dominant role of SO4•− and auxiliary role of •OH/1O2 in ZnCo2O4@NF/PMS system. The reaction sites in CIP molecule easily attacked by ROS were determined, and the possible radical/non-radical degradation pathways of CIP were proposed. This work further unveiled the mechanism of the covalency and electronic configuration in ZnCo2O4@NF. The distinct advantages of the macroscopic catalyst including outstanding catalytic ability and high structural stability provide great possibility for broad industrial application.

Ciprofloxacin degradation in microbubble ozonation combined with electro-generated H2O2 process: Operational parameters and oxidation mechanism

Microbubble ozonation combined with electro-generated H2O2 process (EH2O2-MB-O3) was applied to degrade ciprofloxacin (CIP) as a typical antibiotic in wastewater in this study. The results showed that the performance of CIP degradation and mineralization in EH2O2-MB-O3 process was more efficient than other related processes. Microbubble ozonation and electro-generated H2O2 showed obvious synergistic effect on enhanced CIP removal in EH2O2-MB-O3 process. The O3 dosage, applied current and initial pH in EH2O2-MB-O3 process were optimized as 12.5 mg/min, 50 mA and 7.0 (uncontrolled). Under the optimal conditions, CIP could be degraded completely within 60 min and the TOC removal efficiency of 28.85% could be achieved within 90 min in EH2O2-MB-O3 process. The corresponding ozone utilization efficiency was close to 100%. More efficient ROS generation was observed in EH2O2-MB-O3 process, especially •OH, compared with other related processes. The contribution rates of •OH, 1O2, O3 and O2.- to CIP removal were determined as 66.79%, 23.57%, 6.67% and 2.98% in EH2O2-MB-O3 process, respectively. The electro-generated H2O2 was clarified to contribute to not CIP removal but ROS generation. Three CIP degradation pathways were proposed according to identified degradation intermediates, which indicated that pyridone structure of quinoline and piperazine ring in CIP molecule could be destroyed more easily than benzene ring of quinoline, and the hydroxylation seemed to prevail in these CIP degradation pathways due to •OH electrophilic addition reaction probably. The removal of other antibiotics in EH2O2-MB-O3 process also depended on not ozone direct oxidation but •OH oxidation mainly.

MOF-derived FeCo carbon nanomaterials with abundant oxygen vacancies as highly efficient peroxymonosulfate catalyst for ciprofloxacin degradation

In this work, the FeCo-NB@C catalysts were prepared via calcination with FeCo-MOF as a precursor for highly efficient activation of peroxymonosulfate (PMS). SEM and XPS indicated that FeCo-NB@C possesses mass metal active sites and abundant oxygen vacancies. A synergistic effect (synergy indices 4.6) was observed in the FeCo-NB@C600/PMS process. The ciprofloxacin (CIP) could be almost degraded completely within 15 min in the optimal conditions. It was noted that FeCo-NB@C600/PMS process still performed well on CIP removal under multiple inorganic anions and real water matrix conditions. Radical quenching experiments, EPR analysis, and contribution calculation identified that SO4•−, •OH, and other ROS (O2•− and 1O2) played dominant role in CIP degradation, accounting for 60.24%, 20.19%, and 17.46%, respectively. The redox cycle of Co2+/Co3+ and Fe2+/Fe3+ induced the production of SO4•− and further formed •OH, etc. In addition, the formation of O2•− was confirmed by the role of oxygen vacancies rather than O2 through a series of designed experiments. Furthermore, the characterization results illustrated that FeCo-NB@C600 was largely unchanged with low ion leaching after three times cycles in PMS activated process, indicating the excellent stability and reusability of FeCo-NB@C600. Finally, the results of CIP degradation pathways and toxic evaluation revealed the low ecotoxicity of the intermediate products. This study demonstrates the synergistic catalytic mechanism of bimetallic catalysts in the persulfate activation, promising to realize sustainable and efficient water treatment technology.

Degradation of ciprofloxacin by persulfate activated by Fe(III)-doped BiOCl composite photocatalyst.

Fe-BOC-X photocatalyst was successfully prepared by solvothermal method. The photocatalytic activity of Fe-BOC-X was determined by ciprofloxacin (CIP), a typical fluoroquinolone antibiotic. Under sunlight irradiation, all Fe-BOC-X showed better CIP removal performance than original BiOCl. In comparison, the photocatalyst with iron content of 50 wt% (Fe-BOC-3) has excellent structural stability and the best adsorption photodegradation efficiency. The removal rate of CIP (10mg/L) by Fe-BOC-3 (0.6g/L) reached 81.4% within 90min. At the same time, the effects of photocatalyst dosage, pH, persulfate, persulfate concentration, and combinations of different systems (PS, Fe-BOC-3, Vis/PS, Vis/Fe-BOC-3, Fe-BOC-3/PS, and Vis/Fe-BOC-3/PS) on the reaction were systematically discussed. In reactive species trapping experiments, electron spin resonance (ESR) signals revealed that the photogenerated holes (h+), hydroxyl radical (•OH), sulfate radical (•SO4-), and superoxide radical (•O2-) played an important role in CIP degradation; hydroxyl radicals (•OH) and sulfate radicals (•SO4-) play a major role. Various characterization methods have demonstrated that Fe-BOC-X has larger specific surface area and pore volume than original BiOCl. UV-vis DRS indicate that Fe-BOC-X has wider visible light absorption and faster photocarrier transfer and provides abundant surface oxygen absorption sites for effective molecular oxygen activation. Accordingly, a large number of active species were produced and participated in the photocatalytic process, thus effectively promoting the degradation of ciprofloxacin. Based on HPLC-MS analysis, two possible decomposition pathways of CIP were finally proposed. The main degradation pathways of CIP are mainly due to the high electron density of piperazine ring in CIP molecule, which is mainly attacked by various free radicals. The main reactions include piperazine ring opening, decarbonylation, decarboxylation, and fluorine substitution. This study can better open up a new way for the design of visible light driven photocatalyst and provide more ideas for the removal of CIP in water environment.

Fe-doped kelp biochar-assisted peroxymonosulfate activation for ciprofloxacin degradation: Multiple active site-triggered radical and non-radical mechanisms

In this study, a novel iron-doped kelp-derived biochar (KBC) (Fe-KBC) was prepared via a combination of hydrothermal carbonization and pyrolysis, characterized, and tested for ciprofloxacin (CIP) degradation via peroxymonosulfate (PMS) activation. The CIP removal in KBC800/PMS was remarkably improved in Fe-KBC800/PMS from 63.38% to 97.48%, under optimised condition (CIP 10 mg L−1, KBC800/Fe-KBC800 0.1 g L−1, PMS 0.5 mM). It was demonstrated that the CIP degradation in Fe-KBC800/PMS was dominantly attributed to the enhanced electron transfer and the generation of radical (SO4−) and non-radical (1O2) species, on the surface reactive sites of Fe-KBC800, such as defects, O−C=O in graphitic structures, and Fe-oxides, which were induced by the doped Fe. Those also suggest that the Fe was doped via substituting H+ in CHx and K+, as well as bonding with O in C−O. The Fe-KBC800/PMS showed an excellent degree of mineralization of CIP and the possible CIP degradation pathways were proposed based on identified intermediates. The performance of Fe-KBC800/PMS was not significantly affected by reuses and co-existing ions, i.e., K+, Na+, Ca2+, Cl−, and SO42−, while it was inhibited by Mg2+, HCO3−, H2PO4−, HA, and in natural groundwater, which may affect PMS activation. However, it was greatly enhanced by simply increasing PMS dose. The results in this study provides new insights into the reactions in metal-biochar composites and PMS activation thereby, emphasizing the great potential of Fe-KBC800/PMS in the control of refractory organics in aqueous phase.

Dual promoted ciprofloxacin degradation by Fe0/PS system with ascorbic acid and pre-magnetization

As a widely used and hard-to-degrade pharmaceuticals and personal care product (PPCP), ciprofloxacin (CIP) was frequently found in water environment and the detected concentration was gradually increased. Although zero-valent iron (ZVI) has been shown to be effective in destroying refractory organic pollutants, the practical application and sustained catalytic performance is not satisfactory. Herein, introduction of ascorbic acid (AA) and employment of pre-magnetized Fe0 was achieved to maintain a high-concentration of Fe2+ during persulfate (PS) activation. Pre-Fe0/PS/AA system presented the best performance for CIP degradation, achieving almost complete elimination of 5 mg/L CIP within 40 min in the reaction conditions of 0.2 g/L pre-Fe0，0.05 mM AA and 0.2 mM PS. The CIP degradation retarded as excess pre-Fe0 and AA were added, therefore, the optimum dosages of pre-Fe0 and AA were determined to be 0.2 g/L and 0.05 mM, respectively. The CIP degradation gradually decreased as the initial pH increased from 3.05 to 11.03. The presence of Cl−, HCO3−, Al3+, Cu2+ and humic acid significantly influenced the performance of CIP removal, while Zn2+, Mg2+, Mn2+, and NO3− slightly affected the CIP degradation. Combined with the results of HPLC analysis and previous literature, several possible degradation pathways of CIP were proposed.