Diclofenac In Aqueous Solution Research Articles

Influence of iron content in palladium catalysts supported on alumina and their reduction conditions on the hydrodechlorination of diclofenac in aqueous solutions

Using the method of wet impregnation of alumina with iron and palladium nitrates, 1Pd0.5Fe and 1Pd10Fe catalysts modified with iron oxides were prepared with a target content of 1 wt % Pd, 0.5 or 10 wt % iron. The catalysts were compared with each other and with the monometallic catalyst 1Pd in the hydrodechlorination (HDC) of diclofenac (DCF) in dilute aqueous solutions at 30°C in batch and flow reactors after high-temperature (320°C) and mild (30°C) reduction; the latter was carried out in a batch or flow reactor. Using X-ray photoelectron spectroscopy (XPS), it was shown that after reduction at 320°C the surface of catalysts contains mainly Pd0, Fe2+ and Fe3+. The surface Fe2+/Fe3+ ratio increases as the iron content decreases. The reduction of Pd2+ to Pd0 is possible already at 30°C, but it proceeds much worse on the surface of 1Pd0.5Fe compared to 1Pd10Fe. According to XPS data, temperature-programmed reduction and infrared spectroscopy of diffuse reflection of adsorbed CO, modification with iron oxides increases the palladium content on the surface compared to 1Pd, promotes the emergence of new Pd–O–Fe centers, and affects the ability of palladium to be reduced. These effects increase with increasing iron content. Iron-modified catalysts reduced at 320°C showed similar activity and stability in the conversion of DCP in flow-through and batch systems. Unlike 1Pd0.5Fe, the 1Pd10Fe catalyst is highly efficient and stable even after mild reduction at 30°C. Under flow conditions with comparable DCF conversion, it provides increased selectivity in the HDC reaction of diclofenac compared to 1Pd, which is also active in hydrogenation.

Synthesis and characterization of Fe(III)-doped beta-cyclodextrin-grafted chitosan cryogel beads for adsorption of diclofenac in aqueous solutions: Adsorption experiments and deep-learning modeling

Diclofenac (DCF) is frequently detected in aquatic environments, emphasizing the critical need for its efficient removal globally. Here, we present the synthesis of Fe(III)-doped β-CD-grafted chitosan (Fe/β-CD@CS) cryogel beads designed for adsorbing DCF in aqueous solutions. The beads exhibited an average size of 2.94 ± 0.66 mm and a point of zero charge of 8.03. Adsorption experiments demonstrated that the Langmuir kinetic model provided the most accurate description of the kinetic data, while the Redlich–Peterson isotherm offered the best fit for the equilibrium data. The beads showcased a theoretical maximum adsorption capacity of 712.3 mg/g for DCF, with the adsorption process being identified as exothermic. DCF adsorption on the beads was attributed to hydrogen bonding, metal cation-π interactions, and electrostatic interactions. Reusability tests exhibited that the beads could be regenerated using 0.1 M NaOH. To perform deep learning modeling, adsorption experiments (n = 17), designed utilizing central composite design (CCD), were conducted in duplicate. The CCD framework incorporated input variables such as initial DCF concentration, adsorbent dosage, and solution pH, while the output variable was the DCF removal rate. Utilizing the adsorption data, an artificial neural network (ANN) model was constructed with a topology of 3: 7:10:1, featuring 3 input variables, 7 neurons in the first hidden layer, 10 neurons in the second layer, and 1 output variable. Employing the ANN model data, 3-D response surface plots were generated to elucidate the relationship between input variables and DCF removal rate. Additional adsorption tests were conducted to evaluate the developed ANN model, affirming its reliable predictability for the DCF removal rate. Analysis of the relative importance of the input variables revealed the following order of importance: solution pH (100 %) > adsorbent dosage (75.2 %) > initial DCF concentration (57.7 %).

HYDRODECHLORINATION OF DICLOFENAC IN AQUEOUS SOLUTION OVER PD/ZRO2 AND PD/ZRO2SIO2 CATALYSTS

Pd/ZrO2 and Pd/ZrO2SiO2 catalysts prepared by wet impregnation and reduced with H2 under mild (30 °C, aqueous suspension) or harsh (320 °C) conditions were compared in the hydrodechlorination of the microecotoxicant diclofenac in aqueous solution at 30 оС. According to TPR and XPS data, the addition of SiO2 to the support reduces the degree of metal-support interaction and facilitates the reduction of palladium. Despite the lower Pd0 fraction, the Pd/ZrO2 catalyst was more active in the batch reactor: after reduction at 320 °С, it slightly, and after mild reduction, signi cantly (7 times) exceeded Pd/ZrO2SiO2 in catalytic activity. XRD and TEM showed a wider size distribution of palladium nanoparticles in the Pd/ZrO2 sample, while low-temperature N2 adsorption, XPS, and TPR demonstrated better accessi-bility of palladium on the Pd/ZrO2 surface due to reduced decoration with support components and increased pore size. These features explain the increased activity of Pd/ZrO2. Testing in the ow system demonstrated higher DCF conversion in the presence of catalysts reduced at 320°C and higher stability of Pd/ZrO2SiO2 compared to Pd/ZrO2. The stability is ensured by the increased reducibility of Pd2+ with H2 and by the developed surface of Pd/ZrO2SiO2, which prevents deactivation under the action of HCl released in hydrodechlorination.

Insights into catalyst-free, highly effective degradation of pharmaceutical contaminant in aqueous solution by a dielectric barrier discharge system

The emerging pharmaceutical wastewater including non-steroidal anti-inflammatory drugs has posed a serious threat to the ecological environment and human health, and therefore effective treatment technologies are being urgently needed. Herein, a novel horizontal continuous-flow dielectric barrier discharge (DBD) system without catalyst was developed for the highly effective degradation of diclofenac in aqueous solution. The degradation efficiency of 10 mg/L diclofenac reached about 90% in 14 min, and the corresponding energy efficiency was 0.181 g/kWh. Furthermore, the treated water quality was evaluated in terms of TOC, BOD5/COD and toxicity. The biodegradability rapidly improved with the increasing of DBD treatment time as be expected, although the mineralization efficiency of diclofenac was still low. To gain insight into the degradation mechanism, short-lived transient and long-lived species have been identified during DBD process, in which transient species (·OH, ·O2–) were the major contribution to the oxidation of diclofenac. Furthermore, based on the intermediates identified by LC-MS, a possible degradation pathway of diclofenac by DBD system in aqueous solution was proposed. Therefore, the novel DBD reactor with horizontal continuous-flow appears to be more promising for the treatment of pharmaceutical wastewater in practical applications.

UiO-67-derived bithiophene and bithiazole MIXMOFs for luminescence sensing and removal of contaminants of emerging concern in wastewater

The UiO-67-type MIXMOF [Zr6O4(OH)4(PhPh)5(TzTz)], containing a blue-emitting bithiazole linker, is a potential multifunctional material for environmental remediation, being both a luminescent sensor and an adsorbent for diclofenac in aqueous solutions.

Treatment of diclofenac in aqueous solution by electro-oxidation using BDD electrodes

The consumption of pharmaceutical products such as non-steroidal anti-inflammatories, including 2- [2- (2,6-dichloroanilino) phenyl] acetic acid, better known as diclofenac, has been increasing due to its easy acquisition, as a consequence the environment has had repercussions since it is excreted through the urine, causing a potential risk to be discharged into water bodies and creating persistence in the environment and in the processes of wastewater treatment. Therefore, it is necessary to use alternative processes of advanced oxidation because they have proven to be efficient in the degradation of xenobiotic compounds. The objective of this research was to apply an electro-oxidation system and photoelectro-oxidation by boron-doped diamond (BDD) electrodes using a BDD-BDD configuration to determine the operation variables for the oxidation of diclofenac in aqueous solution. The optimal conditions of the study were: current intensity of 1 A (current density (J) = 25.29 A / m2), the pH of the sample (5-6); NaCl as supporting electrolyte, in the absence of UV light, and treatment time of 360 minutes. The removal efficiency of diclofenac was 97.8 %, the TOC, COD showed efficiencies of 64.4 % and 89.3 %, respectively, whereas the biochemical oxygen demand (BOD5) decrease after of treatment. The degradation kinetic of diclofenac was adjusted to a pseudo first order model, with a half-life time of 63.89 minutes and a k = 1.08 x 10-2 min-1. The removal percentages of diclofenac using liquid chromatography (HPLC) were 99.64 %, 98.76 % and 95.15 % for the concentrations of 150, 50 and 10 mg/l, respectively.

Enhanced photocatalytic performance of visible light driven TiO2/g-C3N4 for degradation of diclofenac in aqueous solution

Emerging contaminants such as diclofenac is frequently detected in wastewater treatment plants as they are not specifically designed for the removal of pharmaceutical effluents, which results in poor removal efficiency. Even though photocatalyst has emerged as an excellent alternative, most of the reported photocatalyst portrays fast recombination rate of electron–hole pair and has slow electron mobility. In order to overcome these shortcomings, in the present work, visible light-driven TiO 2/g-C3N4 photocatalyst was synthesized for the photodegradation of diclofenac in aqueous solution. The morphological and optical properties of the photocatalyst were analysed. The photodegradation efficiency was highly improved even at low g-C3N4 loading, indicating the Z-scheme photocatalyst, successfully overcame the electron–hole pair’s fast recombination rate. The photodegradation efficiency was represented as a function of all independent variables, using a second-order quadratic model. Response surface methodology (RSM) was used to optimize the degradation process. A maximum degradation efficiency (93.49%) was achieved at the optimum conditions (irradiation time = 90 min, initial solution pH = 5, initial DCF concentration = 5 ppm and g-C3N4 loading = 0.3g/g TiO 2). The as developed photocatalyst is found to be highly stable as it showed a satisfactory recyclability. The process followed a pseudo-first-order reaction. Photodegradation of diclofenac also resulted in ten intermediates as identified using LCMS analysis.

Oxidation of diclofenac in water by sodium hypochlorite: Identification of new degradation by-products and their ecotoxicological evaluation

Diclofenac (DCF) is the most widely prescribed non-steroidal anti-inflammatory drug in the world and it has been detected in drinking and surface waters. In this paper, the effect of chlorination process on DCF in aqueous solutions was investigated and the structures of 14 isolated degradation by-products (DPs), of which nine are new, have been determined from combining mass spectrometry and nuclear magnetic resonance data and justified by a proposed mechanism of formation beginning from the parent drug. Some degradation by-products show only one phenyl, others are dimers or trimers of the parental compound, which has undergone oxidative decarboxylation of the side chain and/or chlorination of this or one or both aromatic rings. Ecotoxicological bioassays evidenced the following sensitivities D. magna < R. subcapitata < A. fischeri. The isolated DPs (DP1−8, except for DP9) exhibited effects ≥ 50 % in the exposed microalgae and crustaceans showing toxicities mainly ranked from slight to acute.

Trimethylamine functionalized clay for highly efficient removal of diclofenac from contaminated water: Experiments and theoretical calculations

The importance of the adsorption process and growth demand for using of cost-effective methods has increased the use of low-cost inorganic sorbents. In this study, a batch system was used to remove diclofenac sodium (DF) using pumice modified with trimethylamine (TMAP). Analysis of FTIR, XRF, SEM and BET were used for determining the adsorbent properties. Adsorbent dosage (0.1-1.5 g/L), contact time (0-90 min), solution pH (3-11) and initial DF concentration (0-1000 mg/L), parameters affecting the adsorption process, were investigated. Results of the laboratory data fitted using six isotherm models and the obtained results of Temkin model (R2=0.9762) is better described how the equilibrium results changes. Also, Langmuir isotherm showed that the amount of maximum adsorption capacity at pH = 3, T= 25°C, DF concentration of 1000 mg/L and contact time of 90 min using adsorbent dosage 1.5 g/L was 387.25 mg/g. The pseudo-second-order kinetic model (R2=0.9997) showed better description of the experimental data. Finally, the results showed that modified pumice was able to remove diclofenac in aqueous solution as a low-cost adsorbent.

Degradation of Diclofenac in Aqueous Solutions under Conditions of Combined Homogeneous and Heterogeneous Photocatalysis

The sorption and photocatalytic activities of metal–ceramic composites synthesized via self-propagating high-temperature synthesis (SHS) in the degradation of diclofenac (DCF) is studied. The phase composition and optical properties of the composites are studied, along with the bandgap energy of semiconductors that form part of a ceramic matrix were determined from electronic absorption spectra. The effects the phase composition, UV irradiation time, amount and nature of the added catalyst (H2C2O4, H2O2), and the composite’s weight have on the oxidative destruction of organic contaminant are studied to optimize the catalytic process. The combination of heterogeneous catalysis using composites based on boron and sialon with the homogeneous photo-Fenton system demonstrate the highest efficiency in the degradation of diclofenac.

Preferential growth of nickel hydroxide through the controlled release of base from acrylamide-crotonic acid hydrogels

This work describes the use of acrylamide/crotonic acid hydrogels as a NaOH dosing system to regulate the preferential growth of Ni(OH)2 nanoparticles. For this purpose, acrylamide/crotonic acid hydrogels were synthesized, in different proportions, in aqueous solutions to 10% monomers, with 1% cross-linking agent, 2% initiator and 3% accelerator. The swelling kinetics was determined at 25 ​°C in distilled water and in aqueous NaOH solutions with pH 13. The hydrogel with NaOH was introduced in NiCl2 solutions, and an easily removable green solid was formed on the surface. It was observed that hydrogels swollen before equilibrium promote the growth of Ni(OH)2 a by stacking blades, as detected by the intensity of the plane (001), while hydrogels that reached equilibrium promote lateral growth along the plane (100). Therefore, hydrogel is able to regulate the preferential growth of Ni(OH)2 particles that were also tested a photocatalyst in the degradation of diclofenac in aqueous solution.

Key factors controlling the durability of a Cu-doped TiO2 photocatalyst

This study evaluates the durability of a Cu-doped TiO2 photocatalyst for the mineralization of diclofenac in aqueous solution up to 20 cycles under UV–vis light irradiation (300 nm < λ < 600 nm). The photocatalytic activity decreases over time. The photocatalytic activity at the 20th cycle is 33% lower than that at the 1 st cycle. Meanwhile, the population of photogenerated electrons after 20 cycles is 20% lower than the initial value, as probed by light-induced IR absorption spectroscopy. The bulk structure of the photocatalyst remains unchanged following the repeated uses. The chemical states of the principal elements, Ti and O, are more or less the same among the used samples. In the case of the Cu dopant, however, the coordination structure is not completely preserved. XANES and EXAFS recognize qualitatively different structures after the repeated uses. Based on XANES, the Cu species initially exists in the +2 oxidation state. Its oxidation state then somewhat decreases after the uses, probably due to reductions by the photogenerated electrons. The Cu species are proposed to be responsible for dictating the electron population, and hence, the photocatalytic activity.

Comparative Study of the Degradation of the Diclofenac Drug Using Photo-Peroxidation and Heterogeneous Photocatalysis with UV-C and Solar Radiation

Diclofenac has been detected in water and terrestrial matrices, causing severe changes in the environment. This is due to the fact that it is one of the most widely used nonsteroidal anti-inflammatory drugs in the world. The advanced oxidation processes (AOPs) of photo-peroxidation and heterogeneous photocatalysis were tested in this work using UV-C and solar radiation to degrade diclofenac in aqueous solutions. To monitor the efficiency of the degradation processes an ultrahigh performance liquid chromatography with ultraviolet detection at a wavelength of 285 nm was applied. Both processes were found to be efficient (> 78%) after 60 min of treatment, being possible to determine the reaction kinetics for each one of them. Intermediate formation was also observed after 60 min which were also degraded by increasing the treatment time to 120 min. For the treatments using UV-C radiation, an order of 1.0 was observed, while the treatments that applied solar radiation obtained an order of 0.2 for the photocatalysis and 0.8 for photo-peroxidation.

Magnetite activated carbon/chitosan composite from biomass for removal of diclofenac in aqueous solution

Diclofenac (DCF) is a type of micropollutant from pharmaceutical waste which brings adverse effect to the aquatic environment if the wastewater is not well-treated. The impregnation of biopolymer on activated carbon has recently gained increasing attention to improve the removal efficiency of micropollutant from wastewater. Magnetite rice husk activated carbon/chitosan composite (MACCS) with high adsorption capacity was developed in this study by modifying rice husk activated carbon (RHAC) with iron oxide (Fe3O4) nanoparticles and cross-linked with chitosan. The adsorption performance of the synthesized MACCS was compared with rice husk activated carbon (RHAC) and magnetite chitosan (MCS) for DCF removal from aqueous solution. The physical and chemical properties of the synthesized biosorbents were investigated via scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). MACCS was identified as the best performing biosorbent and its DCF removal ability was further tested in batch with different parameters. The parameters reported in this study were solution pH and the synthesis ratio of activated carbon and chitosan. The most effective adsorption of DCF with MACCS was achieved at solution pH of 2.5 and activated carbon to chitosan ratio of 1:2. In acidic condition, the perfect coating of chitosan which contained abundance of amine group attached on the RHAC with high porosity had achieved 94% removal of DCF with maximum adsorption capacity of 270 mg/g. Besides, the MACCS could easily be separated from the aqueous solution due to its magnetic property. From the results, the MACCS biosorbent showed its potential to be an excellent alternative adsorbent for the removal of micropollutant from wastewater.

Adsorption of Diclofenac from Aqueous Solution onto Carbon Xerogels: Effect of Synthesis Conditions and Presence of Bacteria

Different carbon xerogels (CXs) were synthesized by the polymerization of resorcinol (R) and formaldehyde (F) catalyzed by cesium carbonate (Cs), and by varying the molar ratio R/Cs. The CXs were labeled as XCs-100, XCs-500, XCs-1000, and XCS-2000, corresponding to the R/Cs ratio of 100, 500, 1000, and 2000, respectively. The surface chemistry of the CXs varied very slightly with the R/Cs ratio because the point of zero charge (pHPZC) and the concentrations of basic and acid sites were almost independent on the R/Cs ratio. The surface areas of the four CXs decreased slightly by increasing the R/Cs ratio; however, XCs-500 presented the highest volume of pores and mesopores and mesopore surface area. At a concentration of diclofenac (DCF) at equilibrium of 800 mg/L, the adsorption capacities of XCs-100, XCs-500, XCs-1000, and XCs-2000 towards DCF in aqueous solution were 132.0, 184.6, 126.5, and 126.4 mg/g, respectively. Hence, the adsorption capacity of XCs-500 was about 1.4 times larger than those of the other CXs. The adsorption capacity of XCs-500 was reduced by increasing the solution pH due to electrostatic interactions, whereas the adsorption capacity was increased by raising the temperature, confirming that the adsorption was endothermic. The bacteria Escherichia coli adhered to the surface of XCs-500 forming a biofilm, and the presence of bacteria enhanced 1.3 times the adsorption capacity of XCs-500 towards DCF from water solutions.

Degradation of diclofenac in aqueous solution by ionizing radiation in the presence of humic acid

Diclofenac (DFC) is becoming a ubiquitous pollutant and pose a risk to ecosystem and human beings, which is usually used as a nonsteroidal anti-inflammatory drug for treating painful diseases. In this study, the degradation of DFC in aqueous solution by ionizing radiation was investigated in the presence of various concentrations of humic acid, due to its wide existence in water matrix as natural organic matter (NOM). The experimental results showed that the removal efficiency of DFC was 80.8% at 0.8 kGy absorbed dose and initial concentration of 30 mg/L. The DFC degradation by ionizing radiation could be described by pseudo first-order kinetics model. Humic acid had negative influence on the degradation efficiency of DFC, which decreased from 80.8% to 62.9% when humic acid concentration was 30 mg/L, mainly due to the competition between humic acid and DFC for OH radicals. Several intermediate products were identified by LC-MS analysis during DFC degradation process, and a possible degradation pathway of DFC by ionizing radiation was proposed.

Determination of the Kinetic Behavior of Diclofenac in Aqueous Solution by UV Light Radiation

Diclofenac (DCF) is one of the most widely used non-steroidal anti-inflammatory drugs worldwide, and several studies have reported adverse effects on the environment, in plants and animals; so, it is classified as an emerging pollutant. There are several alternatives for its removal; however, it is necessary to study the way in which the DCF is degrading to offer more effective removal techniques, since the traditional ones such as chlorination, activated sludge, and biofiltration offer low removal efficiency (20–40%). This work analyzes the kinetic behavior of the photodegradation of DCF and the thermodynamic parameters of the reaction under UV-C-type light radiation. The results obtained indicate that it presents a first-order kinetic promoted by the increase of the temperature. Also, within the evaluated interval (273 to 308 K), the values of the kinetic coefficient (k) range between 0.05 and 0.20 min−1 and the half-life ranges from 3 to 9 min. The reaction is exothermic and spontaneous and gives way to the formation of approximately 6 byproducts, being two with the greatest presence and stability. This suggests that its decomposition route occurs through the dechlorination of the molecule and originate compounds known as carbazoles that have been detected in previous works. It was also found that this mixture of byproducts remained after the degradation of the drug, which is released to the environment, so it is necessary to extend a study on its properties and its possible environmental impact.

Rapid removal of diclofenac in aqueous solution by soluble Mn(III) (aq) generated in a novel Electro-activated carbon fiber-permanganate (E-ACF-PM) process

Electrolysis and permanganate (PM) oxidation are two commonly used technologies for water treatment. However, they are often handicapped by their slow reaction rates. To improve the removal efficiency of refractory contaminants, we combined electrolysis with PM using an activated carbon fiber (ACF) as cathode (E-ACF-PM) for the first time to treat diclofenac (DCF) in aqueous solution. Up to 90% DCF was removed in 5 min by E-ACF-PM process. In comparison, only 3.95 and 27.35% of DCF was removed by individual electrolysis and PM oxidation at the same time, respectively. Acidic condition was more conducive to DCF removal. Surprisingly, soluble Mn(III) (aq) formed on the surface of ACF was demonstrated as the principal oxidizing agent in E-ACF-PM process. Further studies showed that all three components (electrolysis + ACF + PM) were necessary to facilitate the heterogeneous generation of reactive Mn(III) (aq). Moreover, SEM images and XPS spectra of ACF before and after treatment revealed that the morphologies and elemental compositions of reacted ACF were nearly unchanged during the E-ACF-PM process. ACF can be remained active and utilized to the rapid degradation of DCF in E-ACF-PM process even after reused for 20 times. Therefore, the E-ACF-PM process may provide a novel and effective alternative on the generation of reactive Mn(III) (aq) in situ for water treatment by green electrochemical reactions.

Advanced oxidation process based on water radiolysis to degrade and mineralize diclofenac in aqueous solutions

Residual pharmaceutical compounds (PCs) are among the emerging organic contaminants detected in our water cycle. Diclofenac (Dic) is one of the commonly detected pharmaceutical contaminant in aquatic systems. This study was designed to investigate the degradation and mineralization of Dic in aqueous solutions by ionizing radiation emitted from radioactive Co60 under several conditions. Ultra-performance liquid chromatography, ion chromatography and TOC measurements confirmed the radiolytic degradation of Dic. The absorbed doses needed to degrade 99% Dic at 25, 50, 100, 190, 280, and 480 μM were 0.560, 0.950, 1.950, 4.000, 5.400, and 7.400 kGy, respectively. This process follows pseudo-first-order kinetics. The γ-ray/N2O system decreased the dose required to degrade 99% to 1.47 kGy. The presence of bromide anions inhibits degradation. Remarkably, adding H2O2, S2O82−, or N2O promotes mineralization. Conversely, the absence of dissolved oxygen hinders mineralization. This study provides a viable finding that ionizing radiation are useful tolls to remedy water containing pharmaceutical organic compounds.

Degradation of diclofenac by heterogeneous electro-Fenton process using magnetic single-walled carbon nanotubes as a catalyst

Degradation of diclofenac (DCF) from aqueous solution was investigated by the heterogeneous electro-Fenton (EF) process using magnetic single-walled carbon nanotubes (MSWCNTs) as a new catalyst. The effect of parameters including initial pH, current density, initial catalyst concentration, the initial concentration of DCF and air flow rate on the efficiency of DCF removal and electrochemical production of H2O2 were studied. A removal efficiency of 97.8% for DCF and 71.12% for COD was obtained at an initial pH of 5, current density of 20 mA/cm2, MSWCNTs concentration of 80 mg/L, DCF concentration of 10 mg/L, air flow rate of 1 mL/min and reaction time of 120 min. Regarding the removal of DCF and COD, and production of H2O2, the heterogeneous EF process with MSWCNTs catalyst showed higher activity and efficiency than other electro-catalytic degradation systems. The stability tests of MSWCNTs after 5 time application confirmed its performance potential for long-term degradation of DCF in aqueous solutions. Intermediate products such as 2,3-dichlorobenzene and 2,4-dichlorophenol were identified by gas chromatography-mass spectrometry (GC–MS). Based on the identification of reactive species and the intermediate products, a possible mechanism of removal and degradation pathways for DCF was suggested.