Oxidation Of Carbamazepine Research Articles

Accelerated photocatalytic oxidation of carbamazepine by a novel 3D hierarchical protonated g-C3N4/BiOBr heterojunction: Performance and mechanism

A novel 3D hierarchical heterojunction of protonated g-C3N4/BiOBr was fabricated by a facile precipitation method with the protonation pretreatment of g-C3N4. The material was characterized by X-ray spectrometer (SEM), transmission electron microscopic (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV–vis reflectance spectra (UV–Vis DRS) and Brunauer-Emmett-Teller (BET). The photocatalytic activity was systematically evaluated by the degradation of carbamazepine (CBZ) under simulated solar light irradiation. The protonated g-C3N4/BiOBr with mass ratios of 5 wt% (pgB-5) achieved the optimum performance for the CBZ removal and excellent stability. The effects of some key operating parameters were further examined in detail, including photocatalyst dosage, initial solution pH, coexisting inorganic anions (HCO3−, Cl−, NO3−). The enhanced activity was ascribed to the effective charge separation occurring at the tightly contacted interface between two phases, which was revealed by electrochemical impedance spectroscopy (EIS) and photocurrent. Basing on direct evidence of the formed hydroxyl radicals (OH), superoxide radicals (O2−) and holes (h+) by electron spin resonance (ESR), the photocatalytic mechanism was proposed for the charge separation. The reaction intermediates were determined by liquid chromatography coupled with mass spectrometry (LC-MS) and a tentative degradation pathway of CBZ was proposed. This study provided a new insight for the design of novel 3D hierarchical heterojunctions and the degradation of recalcitrant organic contaminants in aquatic environment.

Impact of Phosphate on Ferrate Oxidation of Organic Compounds: An Underestimated Oxidant.

Ferrate (K2FeO4) is a powerful oxidant and up to 3 mol of electrons could be captured by 1 mol of ferrate in the theoretical conversion of Fe(VI)-Fe(V)-Fe(IV)-Fe(III). However, it is reported that the utilization efficiency of the ferrate oxidation capacity is quite low because of the rapid autodecomposition of intermediate iron species, which negatively influences the potential of ferrate on organic pollutants control. We accidentally found that for the ferrate oxidation of carbamazepine (CBZ), bisphenol S (BPS), diclofenac (DCF), and ciprofloxacin (CIP), the determined reaction rate constants were 1.7-2.4 times lower in phosphate buffer than those in borate buffer at pH 8.0. For the reaction of ferrate with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) at pH 7.0, the determined reaction stoichiometries were 1:1.04 in 100 mM phosphate buffer, 1:1.18 in 10 mM phosphate buffer, and 1:1.93 in 10 mM borate buffer, respectively. The oxidation ability of ferrate seems depressed in phosphate buffer. A kinetic model involving the oxidation of ABTS by Fe(VI), Fe(V) and Fe(IV) species was developed and fitted the ABTS•+ formation kinetics well under different buffer conditions. The results showed that phosphate exhibited little influence on the oxidation ability of Fe(VI) and Fe(IV) species, but decreased the specific rate constants of ABTS with Fe(V) species by 1-2 orders of magnitude, resulting in the outcompeting of Fe(V) autodecomposition pathway. The complexation between phosphate anions and Fe(V) species may account for the inhibition effect of phosphate buffer. Considering that many studies regarding ferrate oxidation were carried out in phosphate buffer, the actual oxidation ability of ferrate may be underestimated.

Degradation mechanisms of carbamazepine by δ-MnO2: Role of protonation of degradation intermediates

Carbamazepine (CBZ), a widely used antiepileptic drug, is refractory to biological wastewater treatment. Rapid removal of CBZ is possible using synthetic manganese oxide (δ-MnO2) but the removal mechanisms require further investigation. In this study, CBZ degradation by δ-MnO2 was carried out at different pH to further explore the degradation mechanisms. Results show that CBZ degradation by δ-MnO2 was highly pH dependent, and rapid degradation occurred when pH <2.8. Based on the density functional theory calculations, increasing [H+] not only increased the reactivity of δ-MnO2, but also enhanced the secondary reactions of the intermediates. During the degradation process, protonation of CBZ degradation intermediates, instead of CBZ, played an important role. The overall kinetics of CBZ degradation was then described by the retarded first-order model. The initial rate (rinit) in the model between pH 2.0 and 6.2 was determined to be rinit = (2.41 ± 0.51) × 10−3[CBZ]1.21[MnO2]1.07[H+]1.41. This is the first report revealing that protonation of intermediates from CBZ degradation can improve the CBZ oxidation by δ-MnO2. The pathways of CBZ degradation by δ-MnO2 were also proposed. The results of this study provide a new insight into the processing mechanism.

Simultaneous determination of acetaminophen, pramipexole and carbamazepine by ZSM-5 nanozeolite and TiO2 nanoparticles modified carbon paste electrode

In this present paper, a simple voltammetric method has been reported for the simultaneous determination of acetaminophen (AC), pramipexole (PRX) and carbamazepine (CBZ) using ZSM-5 nanozeolite-TiO2 nanoparticles composite modified carbon paste electrode (ZSM-5/TiO2/CPE). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N2 adsorption-desorption isotherm were used to characterize the structure of synthesized ZSM-5 nanozeolite. Also, cyclic voltammetry (CV), choronoamperometry and differential pulse voltammetry (DPV) were used to investigate the performance of the modified electrode. The oxidation peak currents of AC, PRX and CBZ at the surface of ZSM-5/TiO2/CPE were increased dramatically against CPE and their overpotentials decreased. Also, DPV method was used for the simultaneous determination of three drugs in ternary mixture. The effects of modifier amount, pH and scan rate were investigated on the electrochemical response of AC, PRX and CBZ oxidation. The diffusion coefficient, D, and the catalytic rate constant, kcat, were estimated for the oxidation of AC, PRX and CBZ at the surface of modified electrode. Under the optimized experimental conditions, AC, PRX and CBZ give linear response over the range of 2.5–110, 0.6–105 and 6.0–97 μM, respectively. The detection limits were found to be 0.58, 0.38 and 1.04 μM (S/N = 3) for AC, PRX and CBZ, respectively. The fabricated electrode showed good stability, reproducibility and repeatability as well as high recovery. The practical application of the modified electrode was demonstrated by measuring the concentration of spiked AC, PRX and CBZ in human plasma as real sample. The proposed method is simple, rapid and inexpensive and can be utilized as a valuable analytical tool in quality control of the pharmaceutical industry.

A microbial electro-fenton cell for removing carbamazepine in wastewater with electricity output

High electrical energy is required for the electro-Fenton process to remove pharmaceuticals and personal care products (PPCPs) in wastewater. The aim of this study was to develop a novel and more cost-effective process, specifically a microbial electro-Fenton cell (MeFC), for treating PPCPs in wastewater. Acetylene black was selected as the catalyst for H2O2 electrogeneration and Fe-Mn binary oxide for hydroxyl radical production. In addition to lowering energy needs, the MeFC produced a maximum power density of 112 ± 11 mW/m2 with 1 g/L acetate as a representative substrate and 10 mg/L carbamazepine (CBZ) as a typical PPCP. Comparing with electro-Fenton process, the CBZ removal in the MeFC was 38% higher within 24 h operation (90% vs. 62%). Furthermore, the CBZ removal rate in the MeFC was 10–100 times faster than that in other biological treatment processes. Such enhanced degradation of CBZ in the MeFC was attributed to the synergistic reactions between radical oxidation of CBZ and biodegradation of degradative intermediates. The MeFC provides a promising method to remove PPCPs from wastewater coupling with efficient removal of other biodegradable organics.

Biotransformation of carbamazepine by laccase-mediator system: Kinetics, by-products and toxicity assessment

Abstract Carbamazepine (CBZ) is one of the most detected pharmaceutical compounds around the world, with adverse human and animal health impacts in wastewater effluents. Recently, biocatalytic degradation using ligninolytic enzymes such as laccase along with redox mediators provides a promising approach for their removal from water and wastewater. However, the effects of operational parameters on biotransformation need to be investigated in order to design a robust and efficient process. In this research, central composite design was performed and analyzed using response surface methodology to study the effects of temperature, pH, enzyme concentration and mediator concentration. The adequacy of the developed model was confirmed by the coefficient of multiple regression (R2 = 75.97%) indicating a reasonable model for practical implementation. The results showed that performing the biotransformation at 35 °C, pH 6, with 60 U/L of enzyme concentration and 18 μM of mediator concentration resulted in 95% removal of CBZ. 10,11-Dihydro-10,11-dihydroxy-CBZ and 10,11-dihydro-10,11-epoxy-CBZ were identified as the major metabolites of CBZ oxidation by laccase. The estrogenicity tests indicated that the CBZ with an initial concentration of 4 μM and its biotransformation products had no estrogenic effect. The successful transformation of CBZ demonstrated the potential of the laccase-mediator system for the removal of recalcitrant micro-contaminants.

Electrochemical carbamazepine degradation: Effect of the generated active chlorine, transformation pathways and toxicity

Carbamazepine (CBZ) is a biorecalcitrant pharmaceutical compound frequently detected in wastewater and water bodies which has numerous negative effects on living organisms. In this investigation the effect of electrocatalytically generated active chlorine on CBZ degradation was studied using Nb/BDD or Ti/IrO2 anodes. Subsequently, a response surface methodology based on a factorial plan and central composite design was carried out to determine the contribution of individual factors and to obtain the optimal experimental parameters for CBZ abatement. Electric current and treatment time were found to be the pivotal parameters influencing the degradation efficiency with respective contributions of 45.19% and 35.44%. The anode material had lower influence on the response, however, using an Nb/BDD anode, the oxidation was more effective due to the increased production of OH radicals as well as HClO, Cl and ClO− species. Considering CBZ degradation and energetic consumption, the percentage of degraded CBZ was 88.70 ± 0.35% consuming 1.07 kWh m−3 (at 1.0 A, NaCl concentration of 14 mM after 12.45 min, using Nb/BDD anode). First order kinetic constant (k) value of 0.189 min−1 was obtained at optimal conditions when demineralized water was used for the NaCl supporting electrolyte, while k was lower when tap water or treated wastewaters were used for this purpose. Oxidation of CBZ yielded six aromatic intermediates, identified by gas chromatography - mass spectrometry technique and degradation pathways were proposed. The performed acute toxicity tests indicated an increase during the treatment, which was demonstrated to be mainly attributed to the remnant active chlorine.

Electrochemical Oxidation as Treatment for Contaminated Wastewaters by Carbamazepine: Process Optimization Through Response Surface Methodology

The electrochemical oxidation (ECO) of carbamazepine (CBZ), an antiepileptic drug, has been carried out in this study. A response surface methodology approach (RSM) was used in order to optimize the treatment process for CBZ removal on synthetic effluent. Four different operating parameters (current intensity, treatment time, recycling flow rate, and anode type) were chosen as key factors while a single response (CBZ removal) was considered. In the first part of the study, a factorial design (FD) methodology was carried out in order to evaluate the effects and interactions between the selected factors. Results showed that anode type is the most important parameters affecting CBZ degradation (with 67% of the overall effect) followed by the treatment time, the current intensity, and then the recirculation flow rate. Subsequently, a central composite design (CCD) was conducted in order to optimize the overall process taking into account efficiency (CBZ removal) and energy consumption. The contribution of direct and indirect effects of CBZ electro-oxidation was also investigated. As expected, direct oxidation was the most dominant mechanism during ECO with approximately 66% whereas indirect oxidation contributed with only 12%. Finally, the determined optimal conditions were applied on real pharmaceutical wastewater. Despite the effect matrix, 84% of CBZ was obtained after only 100 min of treatment with 23% of mineralization. Finally, CBZ by-products such as salicylic acid, catechol, and anthranilic have been detected during the oxidation process.

Removal of carbamazepine from MBR effluent by electrochemical oxidation (EO) using a Ti/Ta2O5-SnO2 electrode

This study aims at investigating the electrochemical oxidation (EO) of carbamazepine (CBZ) synthetic solutions and real membrane bioreactor (MBR) effluent using newly developed Ti/Ta2O5-SnO2 electrodes to enhance CBZ removal. The characterization of the prepared Ti/Ta2O5-SnO2 electrodes was performed by using scanning electron microscope, energy dispersive X-ray spectroscope, atomic force microscope, and cyclic voltammetry analyses. The main operating parameters influencing the CBZ removal efficiency in synthetic solutions using Ti/Ta2O5-SnO2 electrodes were evaluated including the applied current density, initial CBZ concentration, pH, and temperature. The optimum removal of CBZ (20mgL−1) and TOC reached 75.5%, and 71.1%, respectively, after 8h of electrolysis, under current density of 9mAcm−2, pH 6, temperature of 30°C, and using 0.1M Na2SO4 as supporting electrolyte. Increasing current density and temperature influenced the CBZ removal, unlike pH which did not have significant influence on CBZ removal. The performance of Ti/Ta2O5-SnO2 electrode was compared with conventional Ti/PbO2 electrode in terms of CBZ removal efficiencies and stability of the electrodes. The results showed that under the same operating conditions, the CBZ removal efficiency of Ti/PbO2 electrode was slightly higher than of Ti/Ta2O5-SnO2 (77.9 and 71.7%, respectively). Nonetheless, the use of this newly developed electrode is more energy-efficient as it required the lowest energy consumption of 60.3kWhm−3 to achieve optimum CBZ removal, in addition to fact that no heavy metals were leached (unlike the PbO2 electrode). Furthermore, a complete degradative removal of real MBR effluents spiked with CBZ was achieved when electrolyzed under the optimized conditions of CBZ synthetic solutions. Overall, the EO based on the use of Ti/Ta2O5-SnO2 electrode was found to be a reliable approach to remove CBZ from contaminated waters, with promising potential for integration with MBR technology to remediate CBZ.

Solar-initiated photocatalytic degradation of carbamazepine on excited-state hexadecachlorophthalocyanine in the presence of peroxymonosulfate

In the field of environmental catalysis, the construction of highly efficient and stable catalytic oxidation processes has raised considerable attention. In this study, a novel solar-initiated photocatalytic oxidation system, FePcCl16/PMS/Sunlight, was established by iron hexadecachlorophthalocyanine (FePcCl16) with peroxymonosulfate (PMS) in the presence of sunlight excitation. Under sunlight irradiation, the phthalocyanine ring of the FePcCl16 is motivated to FePcCl16∗ in the excited state, which activates PMS to generate free radicals or high–valent iron(IV)-oxo intermediates (Fe(IV)=O) to oxidize carbamazepine (CBZ). The system could degrade CBZ effectively and total-organic-carbon removal from solution reached nearly 80% within 90min. FePcCl16 catalytic activity was almost without loss and without iron leaching after twenty recycles, indicating that the FePcCl16/PMS/Sunlight was a stable and efficient photocatalytic oxidation system. Electron paramagnetic resonance, gas chromatography-mass spectrometry and photocatalytic-activity-experiment analysis shows that Fe(IV)=O species, singlet oxygen (1O2), hydroxyl and sulfate radicals (OH, SO4−) are the main active species in the catalytic oxidation of CBZ. Density functional theory (DFT) calculations exhibits that the electronic cloud for excited state FePcCl16∗ is transferred from the porphyrazine ring and peripheral substituents to the central Fe atom and its axial position. The main degradation intermediates and possible degradation pathway of CBZ were proposed by ultra-performance liquid chromatography and high-resolution mass spectrometry (UPLC Synapt G2-S HDMS). This study provides efficient catalytic oxidation support for wastewater treatment.

Photocatalytic oxidation of trace carbamazepine in aqueous solution by visible-light-driven Znln2S4: Performance and mechanism

In this work, visible-light-driven Znln2S4 photocatalyst (band gap 1.98 eV, absorption wavelength 300–600 nm) was synthesized by a facile hydrothermal method for photocatalytic degradation of trace pharmaceutical carbamazepine (CBZ) in aqueous solution, and characterized by UV–Vis diffusive reflectance spectroscopy, BET, SEM and XRD, respectively. It demonstrated that a complete degradation of CBZ was achieved with an optimal Znln2S4 dosage of 30 mg/L under a 100 W iodine-gallium lamp irradiation of 20 min, which afforded the reaction rate constant and half-life being respectively 10.44 times higher and 1/8 less than that obtained by a direct photolysis without Znln2S4 photocatalyst. A negligible influence of initial solution pH on photocatalytic degradation of CBZ was confirmed under the given pH range of 5.0–9.0. The degradation efficiency of CBZ was slightly decreased from 91% to 84% after five consecutive cycles. Hydroxy radical (·OH) plays an important role in CBZ degradation accompanying a synergistic effect of photogenerated hole (h+) and O2− active species during reaction. Further, 44 intermediates were detected by LCMS-IT-TOF technique and tentative degrading pathways were proposed on the basis of the experimental results.

Magnetic cobalt ferrite composite as an efficient catalyst for photocatalytic oxidation of carbamazepine.

A magnetic spinel cobalt ferrite nanoparticle composite (CFO) was prepared via an ultrasonication-assisted co-precipitation method. The morphological structure and surface composition of CFO before and after reaction were investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy, indicating the consumption of iron oxide during photodegradation. X-ray photoelectron spectroscopy and vibrating sample magnetometry confirm the preparation of the ferrite nanoparticle composite and its magnetic properties. The prepared CFO was then used for the photocatalytic degradation of carbamazepine (CBZ) as an example of pharmaceuticals and personal care products (PPCPs) from aqueous solution. The effects of the nanocomposite dosage, contact time, and solution pH on the photodegradation process were investigated. More than 96% of the CBZ was degraded within 100min at 0.2g·L-1 CFO in the presence of UV light. The reactive species for CBZ degradation in the CFO/UV system was identified as hydroxyl radicals by the methanol scavenging method. Combined with the detection of leached iron ions during the process, the CBZ degradation mechanism can be presumed to be heterogeneous and homogeneous photocatalytic degradation in the CFO/UV system. Furthermore, iminostilbene and acridine were detected as intermediate products by GC-MS.

Integrative Advanced Oxidation and Biofiltration for Treating Pharmaceuticals in Wastewater.

Advanced oxidation of active pharmaceutical ingredients (APIs) in wastewater produces transformation products (TPs) that are often more biodegradable than the parent compounds. Secondary effluent from a wastewater treatment plant was treated using UV-based advanced oxidation (LPUV/H2O2 and MPUV/NO3) followed by biological aerated filtration (BAF), and different APIs and their transformation products were monitored. The advanced oxidation processes degraded the APIs by 55-87% (LPUV/H2O2) and 58-95% (MPUV/NO3), while minor loss of APIs was achieved in the downstream BAF system. Eleven TPs were detected following oxidation of carbamazepine (5) and iopromide (6); three key TPs were biodegraded in the BAF system. The other TPs remained relatively constant in the BAF. The decrease in UV absorbance (UVA254) of the effluent in the BAF system was linearly correlated to the degradation of the APIs (for the MPUV/NO3-BAF), and can be applied to monitor the biotransformation of APIs in biological-based systems.

Synergistic effects of ultrasounds in the sonoelectrochemical oxidation of pharmaceutical carbamazepine pollutant

The synergistic effects were evaluated during the oxidation of carbamazepine using a sono-electrochemical process. The sono-electrochemical oxidation was performed using two types of experimental units (having 1L and 100L of working volume, respectively) and containing one anode (Ti/PbO2) and one cathode (Ti). Different operating parameters, including power of ultrasounds, current intensity and reaction time were investigated. The degree of synergy increased when the current intensity decreased, whereas it increased with the power of ultrasounds imposed. The highest value of the synergy degree (33%) was recorded for the lowest current intensity (1.0A) and the highest power of ultrasounds (40W). Likewise, the benefits of ultrasound were observed during a long-term period of treatment of CBZ (30days of experiments without interruption). A relatively high degradation rate was recorded using the sono-electrochemical process (99.5%) (at I=1A, P=40W), compared to a percentage of CBZ degradation of 91% recorded during electrolysis alone (at I=1A, P=0W). Likewise, the scanning electron microscopy views and the measurements of the electrochemical impedance spectroscopy (EIS) revealed that there are not impurities deposited on the surface of electrode in the present of ultrasounds.

Dramatically enhanced Fenton oxidation of carbamazepine with easily recyclable microscaled CuFeO 2 by hydroxylamine: Kinetic and mechanism study

Abstract In this study, an inorganic reductant hydroxylamine was used to enhance the Fenton degradation of carbamazepine by easily recyclable microscaled CuFeO2 in a wide pH range (pH 4.0–9.0). It was found that the addition of hydroxylamine could dramatically enhance the degradation rate and TOC removal of carbamazepine, better than other reductants such as benzoquinone and ascorbic acid. In the CuFeO2-H2O2 Fenton system, only 31% CBZ (50 μmol L−1) was removed at pH of 7.0 in 60 min in the presence of 1.0 g L−1 CuFeO2 and 20 mmol L−1 H2O2, while CBZ can be nearly completely removed in 60 min after the addition of 0.1 mmol L−1 hydroxylamine under the similar conditions. Moreover, CBZ degradation followed the pseudo first-order kinetics in the CuFeO2-H2O2 Fenton system, while in the hydroxylamine enhanced CuFeO2-H2O2 Fenton system, CBZ degradation followed the pseudo second-order kinetics. In the CuFeO2-H2O2 Fenton system, t1/2 value for CBZ degradation was calculated as 114.4 min and the value was greatly decreased to 1.8 min after the addition of hydroxylamine. This hydroxylamine induced dramatic carbamazepine degradation enhancement could be attributed to the hydroxylamine enhanced Fe(III)/Fe(II) and Cu(II)/Cu(I) redox cycles. Hydroxyl radicals were the primary radical species responsible for the carbamazepine degradation. As a microscaled catalyst, micro-CuFeO2 can be easily recovered by gravity settlement and exhibited good catalytic stability during six successive degradation cycles. Therefore, the couple of CuFeO2-H2O2-hydroxylamine is a promising method for oxidative degradation of organic pollutants in the actual aqueous environmental systems.

Photocatalytic Oxidation of Carbamazepine: Application of an Experimental Design Methodology

Carbamazepine is one of the pharmaceutical compounds frequently detected in the receiving waters and water bodies. The main objective of this study was to develop a quadratic model to predict carbamazepine (CBZ) photocatalytic removal through a response surface methodology. A factorial plan (linear model; 24 experiments) was used to determine the contribution of individual factors (pH, CBZ concentration, photocatalyst concentration, and treatment time) and interactions among the factors. Pollutant concentration and treatment time were found to be the most important parameters influencing the oxidation rate, with respective contributions of 19.22 and 71.55 %. Central composite methodology was then applied to determine the optimal experimental parameters for CBZ oxidation. The highest percentage of CBZ removed was 94.67 ± 0.51 %, recorded using a pH of 5, a minimal CBZ concentration of 10 mg/L, a photocatalyst concentration of 1.14 g/L, and a treatment time of 90 min. The effects of different anions (NO3− and SO42−) and cations (Cu2+, Cr3+, Zn2+) were also studied. Copper was found to have both catalytic and inhibitory effects on CBZ removal rate.

Biocatalytic degradation of carbamazepine with immobilized laccase-mediator membrane hybrid reactor

Carbamazepine (CBZ) is one of the most recalcitrant pharmaceutically active compounds routinely detected in wastewater effluent-impacted environment. Biocatalytic degradation with enzymes such as laccase provides a promising approach for the elimination of CBZ. However, the relatively low redox potential of laccase makes its efficient CBZ degradation difficult. Therefore, an environmentally benign and effective mediator is required. In this study, three natural phenolic compounds, namely p-coumaric acid (PCA), syringaldehyde (SYR), and acetosyringone (ACE), were investigated as redox mediators for the enzymatic removal of CBZ by both free and immobilized laccase. Among the tested mediators, PCA resulted in the optimal CBZ removal performance with 60% removal rate (20μM initial CBZ) after 96h incubation with immobilized laccase in a conventional suspension system. The degradation of CBZ was then carried out in a membrane hybrid reactor with the effluent recirculating through suspended biocatalytic TiO2 nanoparticles. The effect of operation parameters including PCA concentrations, initial enzyme activity and operational flux on CBZ removal were investigated. Further CBZ metabolites study identified 10,11-dihydro-10,11-dihydroxy-CBZ (CBZD), 10,11-dihydro-10,11-epoxy-CBZ (CBZE) and acridone as the major metabolites of CBZ oxidation by laccase. The toxicity tests determined by algal viability using the fluorometric indicator alamarBlue indicated that the CBZ treatment via the hybrid reactor could effectively remove the toxicity of parent CBZ compound.

Inadequacy of carbamazepine-spiked model wastewaters for testing photocatalysis efficiency

The study was performed in order to clarify whether carbamazepine-spiked solutions used as model wastewaters are suitable for the assessment of carbamazepine removal from real secondary municipal effluents by photocatalytic oxidation in the presence and absence of activated carbon. Therefore, carbamazepine (10mgL−1) was dissolved in deionized water or in secondary municipal effluent. Photocatalytic oxidation of these model wastewaters was carried out with TiO2 “P25” (100mgL−1) and UV-A lamps in the absence and in the presence of 20mgL−1 powdered activated carbon (PAC). Carbamazepine was analyzed photometrically. In deionized water at pH5.5, carbamazepine was nearly completely removed with a UV dose of 6.48kJL−1. A similar efficiency of photocatalytic oxidation of carbamazepine added to secondary effluent was observed when the suspension pH was 2.7, while at pH8 and 10.6, carbamazepine removal from spiked secondary effluent with the same UV dose was only 40 and 60%, respectively. Although PAC addition resulted in an initial adsorptive carbamazepine reduction of 20 to 35% from the model wastewaters, it did not lead to markedly enhanced carbamazepine removal in the subsequent photocatalysis phase. During photocatalytic oxidation of unspiked secondary effluent (initial carbamazepine concentration: 133ngL−1) at pH7.3 with and without PAC, carbamazepine concentrations were analyzed by HPLC/MS/MS. While PAC addition resulted in the adsorption of about 90% of the initial carbamazepine, photocatalysis did not lead to any carbamazepine removal at all. This indicates that the experiments with spiked model wastewaters – even in a secondary effluent matrix – are absolutely inadequate for predicting photocatalytic carbamazepine removal under real conditions.

Removal of carbamazepine from aqueous solution using sono-activated persulfate process

This study investigated systematically the removal of carbamazepine (CBZ) in solution using the combination of ultrasound and persulfate anions to identify the factors affecting the kinetics of the process. The effects of reaction time, initial persulfate anion concentration, initial CBZ concentration, ultrasonic power input, solution pH and temperature on CBZ removal efficiency were examined. The sulfate radical oxidation of CBZ in the presence of ultrasonic irradiation showed a significant synergistic effect on CBZ removal. It is found that up to 89.4% CBZ removal efficiency was achieved after 120min reaction. The removal process of CBZ in solution could be described using pseudo-first-order kinetics. In this system, sulfate radicals (SO4−) were considered to be the mainly oxidant to remove CBZ while ultrasound power input could affect CBZ removal efficiency significantly. Changing solution pH influenced the CBZ removal efficiency and the best performance would be achieved at pH 5.0.

Online Investigation of Aqueous-Phase Electrochemical Reactions by Desorption Electrospray Ionization Mass Spectrometry.

Electrochemistry (EC) combined with mass spectrometry (MS) is a powerful tool for elucidation of electrochemical reaction mechanisms. However, direct online analysis of electrochemical reaction in aqueous phase was rarely explored. This paper presents the online investigation of several electrochemical reactions with biological relevance in the aqueous phase, such as nitrosothiol reduction, carbohydrate oxidation, and carbamazepine oxidation using desorption electrospray ionization mass spectrometry (DESI-MS). It was found that electroreduction of nitrosothiols [e.g., nitrosylated insulin B (13-23)] leads to free thiols by loss of NO, as confirmed by online MS analysis for the first time. The characteristic mass shift of 29 Da and the reduced intensity provide a quick way to identify nitrosylated species. Equally importantly, upon collision-induced dissociation (CID), the reduced peptide ion produces more fragment ions than its nitrosylated precursor ion (presumably the backbone fragmentation cannot compete with the facile NO loss for the precursor ion), thus facilitating peptide sequencing. In the case of saccharide oxidation, it was found that glucose undergoes electro-oxidation to produce gluconic acid at alkaline pH, but not at neutral and acidic pHs. Such a pH-dependent electrochemical behavior was also observed for disaccharides such as maltose and cellobiose. Upon electrochemical oxidation, carbamazepine was found to undergo ring contraction and amide bond cleavage, which parallels the oxidative metabolism observed for this drug in leucocytes. The mechanistic information of these redox reactions revealed by EC/DESI-MS would be of value in nitroso-proteome research and carbohydrate/drug metabolic studies.