Oxidation Of Carbamazepine Research Articles

Bromate-induced oxidation of carbamazepine and toxicity assessment of transformation products in the freezing-sunlight process: Effects of trivalent chromium

Bromate (BrO3-)-induced pharmaceutical and personal care products (PPCPs) oxidation is enhanced in freezing systems. Reduced forms of metals are widely present, often coexisting with various contaminants. However, their effects on the interaction of PPCPs with BrO3- in ice in cold regions may have been overlooked. Herein we investigated the effects of representative reducing metal Cr(III) on the interaction between the representative PPCP carbamazepine (CBZ) and BrO3- in the freezing system. Our findings demonstrated that the degradation rate constants of CBZ by BrO3- and Cr(III) were 29.4%–60.3% lower than those by BrO3- in ice, revealing the inhibition of Cr(III) on CBZ degradation by BrO3- in ice. In BrO3-/freezing/sunlight system, BrO3- contributed 62.8% to CBZ degradation. In BrO3-/Cr(III)/freezing/sunlight system, Cr(III) promoted the generation of hydroxyl radical (·OH), leading to 51.0% contribution of ·OH to CBZ degradation. Oxidants were consumed by Cr(III) to form Cr(VI) rather than reacting with CBZ, thereby decreasing CBZ degradation by BrO3- in ice. Due to sunlight-induced Cr(VI) reduction in ice, only 0.3% of Cr(III) was converted to Cr(VI) in BrO3-/Cr(III)/freezing/sunlight system. BrO3--induced CBZ degradation rate in ice decreased in order of Fe(II), Cr(III), and Mn(II), which was due to the different reducing capabilities. An effective reduction in comprehensive toxicity of systems followed the freezing-sunlight process, even in the presence of Cr(III). This work sheds new light on the environmental behaviors and fate of PPCPs, brominated disinfection by-products, and reducing metals during seasonal freezing.

Electrochemical sensing platform for anticonvulsant drug carbamazepine detection based on graphitic carbon nitride and tetrabutylammonium chloride ionic liquid

The development of a rapid and straightforward electrochemical approach for the quantification of the anticonvulsant drug carbamazepine (CBZ) is herein presented. Carbon paste electrode (CPE) was bulk modified with a type of two-dimensional conjugated polymer, i.e., graphitic carbon nitride (g-C3N4), and additionally with an ionic liquid tetrabutylammonium chloride (TBACl) to obtain advanced electrochemical sensor for CBZ. Synthesized g-C3N4 material was structurally and morphologically characterized by Raman spectroscopic, FTIR, and SEM/EDX methods. CV experiments showed that the resulting electrode (TBACl-g-C3N4-CPE) has an improved electrochemical response compared to unmodified CPE and g-C3N4-CPE due to the synergistic effect of electrode modifiers, as well as that the CBZ oxidation process is irreversible and diffusion-controlled. After optimization steps concerning the amount of electrode modifiers and the selection of pH of the supporting electrolyte, the analytical performance of TBACl-g-C3N4-CPE was investigated by direct anodic square-wave voltammetry (SWV). The most intensive peak of the target analyte was obtained in Britton-Robinson buffer solution at pH 7.0, whereby the developed SWV method was characterized by a linear concentration range of CBZ from 0.42 to 9.31 µmoL L−1, limit of detection (LOD) of 0.13 µmoL L−1, and relative standard deviation lower than 3 %. The interference study showed that TBACl-g-C3N4-CPE exhibits adequate selectivity for CBZ in the presence of ions/compounds commonly present in the urine matrix. The developed sensor was utilized to determine CBZ in pharmaceuticals and spiked human urine sample with excellent recovery and reproducibility, indicating a good application capability of TBACl-g-C3N4-CPE for monitoring CBZ in different matrices.

Performance and mechanic insights into potassium-oxygen co-doping graphic carbon nitride for UV photocatalytic oxidation of carbamazepine

Graphitic carbon nitride (g-C3N4) has good prospect in the field of photocatalysis, but its small specific surface area and low photogenerated carrier separation efficiency limit the large-scale application in photocatalytic wastewater treatment. In this study, the one-step thermal polymerization method was employed to synthesize potassium and oxygen co-doped g-C3N4 (OCN-3), which was used in photocatalytic degradation of carbamazepine (CBZ). Compared with the original g-C3N4, the pseudo first-order kinetic constant of CBZ degradation by OCN-3 was increased from 0.00820 min−1 to 0.17529 min−1 under UV irradiation. The results of competitive oxidation kinetics experiment demonstrated that ·OH played a main role in CBZ degradation. The photoelectric experiments and calculation based on density functional theory revealed that potassium and oxygen atoms can not only regulate the local electron density, but also reduce the band gap width and promote electron transfer as well as photogenerated carrier separation. Furthermore, OCN-3 was loaded on carbon cloth to prepare supported photocatalyst, which can be conveniently applied in continuous wastewater treatment reactor, and the results shows that the degradation efficiency of CBZ remains over 90% within 600 min continuous operation when the hydraulic retention time was 1.25 h.

Comparative study of organic removal by pre-adsorption oxidation and synchronous adsorption oxidation processes: Performance and mechanism

Both adsorption and oxidation occur and contribute to organics removal in carbonaceous materials based advanced oxidation processes, while the correction of adsorption and oxidation, and the role of adsorption in the veritable removal of organic are not clear. Herein, we investigated the performance of carbamazepine (CBZ) removal by peroxymonosulfate (PMS) activated by magnetic Fe-doped biochar through two models of pre-adsorption oxidation and synchronous adsorption oxidation processes. The adsorption process was better fitted by pseudo-second-order kinetic model and the adsorption mechanism was obtained by comprehensive analysis of equilibrium adsorption capacities, surface functional groups, specific surface area, pore volume, and ID/IG value. It is noted that pre-adsorption highly inhibited the further oxidation of CBZ in 0.5Fe@LSBC700/PMS system due to the occupied catalytic active sites. Total CBZ removal in pre-adsorption oxidation (45 %) was inferior to synchronous adsorption oxidation (∼100 %), as well as the veritable CBZ oxidation removal of 27 % for pre-adsorption oxidation vs ∼100 % in synchronous adsorption oxidation at 30 min. Oxidation degradation of CBZ based on radical oxidation was identified by quenching experiments and electron paramagnetic resonance measurements. This work is conducive to identifying the role of adsorption during the removal of organics in the adsorption-oxidation process, as well as veritable adsorption and oxidation removal of organics.

Peroxymonosulfate oxidation of carbamazepine by Iron-Biochar via nonradical pathways: Singlet oxygen, electron transfer, and Fe (IV)

In this study, the synthesis of Fe@BC (biochar) was successfully achieved using a one-step calcination process. The catalyst exhibited notable pore structures, a considerable specific surface area, and surface functional groups. Heterogeneous catalytic experiments further demonstrated that the CBZ degradation was significantly improved in the Fe2@BC900℃-PMS process, in comparison to alternative catalytic processes. The quenching, ESR analyses, and electrochemical tests (CV, LSV, OCP, and EIS) provided evidence that the CBZ degradation occurred via nonradical pathways involving the participation of 1O2, electron transfer, and Fe (IV). Furthermore, the potential mechanisms of PMS activation in the Fe2@BC900℃-PMS process were systematically elucidated. DFT, LC-MASS tests and ECOSAR suggested that CBZ can be transformed into smaller, less toxic molecules during the treatment. Moreover, the cyclic experiments revealed that the Fe2@BC900℃-PMS process maintained a consistent oxidation capacity for CBZ even after undergoing ten cycles. Based on the above findings, it can be concluded that the Fe2@BC900℃-PMS process could effectively degrade organic pollutants in water.

Ru(III)-Periodate for High Performance and Selective Degradation of Aqueous Organic Pollutants: Important Role of Ru(V) and Ru(IV).

In this study, Ru(III) ions were utilized to activate periodate (PI) for oxidation of trace organic pollutants (TOPs, e.g., carbamazepine (CBZ)). The Ru(III)/PI system can significantly promote the oxidation of CBZ in a wide initial pH range (3.0-11.0) at 1 μM Ru(III), showing much higher performance than transition metal ions (i.e., Fe(II), Co(II), Zn(II), Fe(III), Cu(II), Ni(II), Mn(II), and Ce(III)) and noble metal ion (i.e., Ag(I), Pd(II), Pt(II), and Ir(III)) activated PI systems. Probe experiments, UV-vis spectra, and X-ray absorption near-edge structure (XANES) spectra confirmed high-valent Ru-oxo species (Ru(V)=O) as the dominant oxidant in the process. Because of the dominant role of Ru(V)=O, the Ru(III)/PI process exhibited a remarkable selectivity and strong anti-interference in the oxidation of TOPs in complex water matrices. The Ru(V)=O species can undertake 1-e- and 2-e- transfer reactions via the catalytic cycles of Ru(V)=O → Ru(IV) → Ru(III) and Ru(V)=O → Ru(III), respectively. The utilization efficiency of PI in the Ru(III)/PI process for the oxidation of TOPs can approach 100% under optimal conditions. PI stoichiometrically transformed into IO3- without production of undesired iodine species (e.g., HOI and I2). This study developed an efficient and environmentally benign advanced oxidation process for rapid removal of TOPs and enriched understandings on reactivity of Ru(V)=O and Ru catalytic cycles.

Highly Efficient Electrochemical Oxidation of Carbamazepine Using a Novel Graphene Nanoplatelet-doped PbO2 Electrode: Characteristics, Efficiency, and Mechanism

A novel graphene nanoplatelet (GN)-doped PbO2 electrode was fabricated and utilized to pulse electrochemical oxidize carbamazepine (CBZ) in aquesous solution. The GN-PbO2 electrode differed from a pure PbO2 electrode in that it exhibited higher surface roughness, smaller particle size, larger specific surface area, greater oxidation peak current, smaller charge transfer resistance, and higher oxygen evolution potential. After electrolysis for 90 min, 94.74% of CBZ and 45.15% of chemical oxygen demand could be removed at an initial pH of 3, pulsed frequency of 3000 Hz, current density of 20 mA cm−2, and pulsed duty cycle of 50%. Additionally, the primary electrochemical oxidation mechanism at the GN-PbO2 anode was indirect radical oxidation and the degradation pathway of CBZ in pulsed electrochemical oxidation was investigated and clarified considering the identified intermediate products and theoretical computations. The results demonstrate that pulsed electrochemical oxidation based on GN-PbO2 electrodes is a promising approach to increasing the viability of pharmaceutical wastewater treatment by electrochemical technologies.

Zero-valent tungsten boosted Fenton-like oxidation (Fe(III)/peroxydisulfate) towards long-lasting oxidation of carbamazepine: Performance and mechanism

The slow conversion of the Fe(III)/Fe(II) redox couple arising from Fe(III) accumulation strongly restricts the ongoing generation for reactive oxygen species (ROS) in Fenton/Fenton-like systems. Hereby, micron zero-valent tungsten (μZVW) was applied as a co-catalyst to boost Fe(III) reduction for promoting the Fenton-like activation of peroxydisulfate (PDS), and the oxidation capacity and reaction mechanism of μZVW/Fe(III)/PDS system are investigated with carbamazepine (CBZ) as the target pollutant. The results show that CBZ can be completely degraded by the μZVW/Fe(III)/PDS system within 30 min, μZVW exhibits exceptionally high stability for long-lasting CBZ oxidation during 10 cycling tests. According to a mechanistic analysis, the main ROS responsible for CBZ oxidation include high-valent iron (Fe(IV)), hydroxyl radicals, and sulfate radicals, meanwhile, μZVW can rapidly reduce Fe(III) into Fe(II) and further boost Fenton-like activation of PDS. Fe(III) and PDS can speed up the stepwise oxidation of μZVW to steadily release low-valence tungsten species, which can induce reduction of dissolved oxygen to produce H2O2 and donate electrons to cleave peroxide O-O bonds of H2O2 and PDS to produce ROS. In addition, the self-cleaning function of μZVW makes it efficient to remove CBZ was discovered. Therefore, the finding of this study proposes a novel co-catalyst to boost Fenton-like activation of PDS, which can promote the scientific advances in enhanced Fenton-like oxidation towards realistic use in water remediation.

Electrochemical oxidation of carbamazepine in water using enhanced blue TiO2 nanotube arrays anode on porous titanium substrate

In this study, a blue TiO2 nanotube arrays anode on porous titanium substrate (Ti-porous/blue TiO2 NTA) was successfully fabricated by facile anodization and in situ reduction, and was used to investigate the electrochemical oxidation of carbamazepine (CBZ) in aqueous solution. The surface morphology and crystalline phase of the fabricated anode were characterized by SEM, XRD, Raman spectroscopy and XPS, and the electrochemical analysis confirmed that blue TiO2 NTA on Ti-porous substrate had larger electroactive surface area, better electrochemical performance and higher ⋅OH generation ability than that on Ti-plate substrate. The removal efficiency of 20 mg L−1 CBZ in 0.05 M Na2SO4 solution reached 99.75% at 8 mA cm−2 after 60 min electrochemical oxidation, and the rate constant was 0.101 min−1 with low energy consumption. EPR analysis and free radical sacrificing experiments showed that ⋅OH played a key role in the electrochemical oxidation. The possible oxidation pathways of CBZ were proposed through the identification of degradation products, and the main reactions may involve deamidization, oxidization, hydroxylation and ring-opening. Compared with Ti-plate/blue TiO2 NTA anode, Ti-porous/blue TiO2 NTA anode displayed excellent stability and reusability, and is promising to be used in the electrochemical oxidation of CBZ in wastewater.

Computational study on persulfate activation by two-dimensional carbon materials with various nitrogen proportions for carbamazepine oxidation in wastewater: The essential role of graphitic N atoms.

Two-dimensional carbon materials with various N atom proportions (2D-CNMs) are constructed to clarify the optimal catalyst for carbamazepine (CBZ) oxidation and the inner mechanism for persulfate-based advanced oxidation processes (P-AOPs). Results show that peroxydisulfate (PDS) can be activated by all 2D-CNMs with the order of C3N>C71N>graphene >C2N>CN, while C3N is the only catalyst for peroxymonosulfate (PMS) activation. The C3N with the maximum graphitic N can activate PDS and PMS in a wide temperature range at any pH, and demonstrates the optimal CBZ oxidation performance. Notably, the graphitic N atoms promote P-AOPs from five aspects: (i) electron structure, (ii) electrical conductivity, (iii) electron transfer from persulfate to catalysts, (iv) electron jump of co-system before and after activation, (v) interaction between catalyst and persulfate. The most vigorous activity of C3N is attributed to the greatest number of graphitic N. This work clarifies the essential role of graphitic N atoms with implications for the catalyst design, and facilitates the environmental applications of P-AOPs for micropollutant abatement.

Roles of MnO2 Colloids and Mn(III) during the Oxidation of Organic Contaminants by Permanganate.

Although intermediate manganese species can be generated during the reactions of permanganate (Mn(VII)) with organic pollutants in water, the role of the in situ generated MnO2 colloids in the Mn(VII) oxidation process remained controversial and the contribution of Mn(III) was largely neglected. This study showed that the apparent second-order rate constants (kapp) of Mn(VII) oxidation of methyl phenyl sulfoxide and carbamazepine remained constant with time. However, the degradation of four selected phenolic contaminants by Mn(VII) exhibited an autoaccelerating trend and a linear trend at pH 3.0-6.0 and pH 7.0-9.0, respectively. Multiple lines of evidence revealed that the occurrence of the autoaccelerating trend in the Mn(VII) oxidation process was ascribed to the oxidation of the phenolic organics by MnO2 colloids. The influence of pyrophosphate on the oxidation of different organic contaminants by MnO2 colloids suggests that Mn(III) was also responsible for the autoaccelerating oxidation of organic contaminants by Mn(VII) under specific reaction conditions. The kinetic models revealed that the overall contributions of MnO2 colloids and Mn(III) ranged within 6.6-67.9% during the autoaccelerating oxidation of phenolic contaminants by Mn(VII). These findings advance the understanding of the roles of MnO2 colloids and Mn(III) in the Mn(VII) oxidation process.

Eggshell supported Cu doped FeOx magnetic nanoparticles as peroxymonosulfate activator for carbamazepine degradation

In this study, a composite of eggshell supported Cu doped FeOx nanoparticles(FeCuOx/eggshell) was synthesized using a facile co-precipitation method, morphologies and properties were systematically characterized. Meanwhile, catalytic performance of the FeCuOx/eggshell & peroxymonosulfate (PMS) system for carbamazepine (CBZ) degradation, effect of operation parameters and water matrices on CBZ removal in this system were evaluated. Besides, Reactive Oxygen Species (ROSs) responsible for the oxidation of CBZ were identified through series of experiments, and a possible degradation pathway of CBZ was proposed. Furthermore, possible reaction mechanism, possible decomposition pathways were proposed. Evolution of CBZ solution toxicity was also evaluated. In addition, installation of FeCuOx/eggshell into PAN membrane has been proved to improve stability and reduce metal release.

Removal of Emerging Contaminants from Water Using Cyclodextrin-Based Polymers and Advanced Oxidation Processes: The Case of Carbamazepine

Using a water-insoluble β-cyclodextrin-epichlorohydrin copolymer (β-EPI) as an adsorbent to remove carbamazepine (CBZ), an anti-epileptic drug often found both in hospital and urban wastewater, has been validated. The effect of several physicochemical parameters on CBZ retention onto β-EPI, such as contact time, adsorbent dosage, CBZ initial concentration, pH, salts, and temperature, was assessed. The adsorption process occurs in a very short time, less than 20 min, and depends on CBZ concentration and β-EPI amount used. Changes in pH and salt presence, regardless of the type of cation or anion used, do not significantly affect the system’s efficiency. Desorption experiments were also performed, and methanol has proven to be the best CBZ extraction medium; it was also found that the polymer can be recovered and reused for at least five cycles, which makes it cheap and environmentally friendly. Advanced oxidation processes were also tested for CBZ removal by synthesizing a β-EPI polymer bearing titanium dioxide for adsorption and consecutive photocatalytic degradation of the retained pollutant directly onto the material; the effect of TiO2 amount in the polymer on CBZ oxidation was evaluated. These experiments highlighted the system’s effectiveness, and it was also observed that the H2O2 presence in the solution enhanced the CBZ photodegradation.

Oxygen vacancies and interfacial iron sites in hierarchical BiOCl nanosheet microflowers cooperatively promoting photo-Fenton

Controllable active site construction, crystal structure regulation and efficient charge separation are core issues in heterogeneous photo-Fenton. Herein, abundant oxygen vacancies and well-dispersed interfacial iron sites are simultaneously constructed in hierarchical nanosheet-assembled BiOCl microflowers. The composites exhibit superior performance in photo-Fenton oxidation of carbamazepine (10 mg L−1) with a low H2O2 concentration (1.3 mM). The high performance highly depends on the synergistic effects between oxygen vacancies and iron species. Rather than modulating the valence band, the involvements of oxygen vacancies and iron species could modify the conduction band of BiOCl. The presence of oxygen vacancies promotes the migration of photo-generated electrons and accelerates the redox cycling of ≡Fe(III)/≡Fe(II) to boost the activation of H2O2 to generate hydroxyl radicals, and oxygen vacancies can be well preserved after cyclic use. This work provides understanding on efficient utilization of oxygen vacancies and interfacial iron sites to assist photo-Fenton and the underlying electron transfer mechanism.

Oxidation of micropollutants by visible light active graphitic carbon nitride and ferrate(VI): Delineating the role of surface delocalized electrons

The treatment of recalcitrant micropollutants in water remains challenging. Ferrate(VI) (FeVIO42−, Fe(VI)) has emerged as a green oxidant to oxidize organic molecules, however, its reactivity with recalcitrant micropollutants are sluggish. Our results demonstrate enhanced oxidation of carbamazepine (CBZ) by three types of visible light-responsive graphitic carbon nitride (g-C3N4) photocatalyst in absence and presence of ferrate(VI) (FeVIO42−, Fe(VI)) under mild alkaline conditions. The g-C3N4 photocatalysts were prepared by thermal process using urea, thiourea, and melamine and were named as CN-U, CN-T, and CN-M, respectively. The degradation efficiency of CBZ, in both visible light-g-C3N4 and visible light-g–C3N4–FeVIO42- systems followed the order of CN-U > CN-T > CN-M. The mechanisms for this trend was elucidated by measuring physiochemical properties of the microstructures with various surface and analytical techniques. Results suggest the dominating role of specific surface area and surface delocalized electrons of microstructures in degrading CBZ. Crystallinity, morphology, and surface functional groups may not directly associate with CBZ degradation. The CN-U has higher specific surface area and surface delocalized electrons than CN-T and CN-M and therefore the highest degradation efficiency of CBZ. The surface electrons likely generated O2●- and 1O2 in the visible light-g-C3N4 system. The additional oxidants, FeV and FeIV in the visible light-g–C3N4– FeVIO42− system led to higher degradation efficiency than the visible light-g-C3N4 system. Results suggest that the surfaces of g-C3N4 may be prepared preferentially with high levels of delocalized electrons at the surface of microstructures to enhance degradation of micropollutants.

Electrochemical Advanced Oxidation of Carbamazepine: Mechanism and optimal operating conditions

Effective electrochemical degradation of carbamazepine (CBZ) in water was accomplished with minimal energy and chemical requirements, showing that electrochemical Advanced Oxidation Processes (eAOPs) with a Boron-Doped Diamond (BDD) anode are a promising method for the in situ degradation of contaminants of emerging concern (CECs). The influence of several operating parameters (i.e., pH, temperature and initial anolyte and pollutant concentrations) was determined through the Taguchi optimization method. Optimal conditions corresponded to 1 μM CBZ, pH 2, 30 °C, 10 mM Na2SO4 and 50 A m−2, resulting in complete CBZ removal in less than 5 min. Complementary scenarios with different ion species, energy sources and current densities further corroborated the suitability of the optimum. Moreover, they revealed that the optimal conditions were driven by the presence of both SO42− and NO3− ions in solution. Hence, the optimal degradation results were also attained when replacing HNO3 by NaNO3, which allowed to operate without prior pH adjustments. The contribution of •OH and SO4•− radicals was studied through scavenging tests and it was for the first time tentatively ascribed to the Oxygen Evolution Reaction (OER), since the selection of the operating potential influences the type of oxidative species present. Finally, the primary transformation products formed during CBZ degradation under optimal conditions were investigated.

Electrochemical monitoring of carbamazepine in biological fluids by a glassy carbon electrode modified with CuO/ZnFe2O4/rGO nanocomposite

This paper illustrates the modification of the glassy carbon electrode (GCE) with the synthesized ternary nanocomposite of graphene, zinc ferrite nanoparticles (ZnFe2O4), and copper oxide (CuO) for the determination of carbamazepine (CBZ) in the biological fluids. The large surface area of GO, the conductivity of CuO nanoparticles, and electron transfer sites of ZnFe2O4 provide a sensitive electrochemical sensor for the quantitative analysis of CBZ. The physicochemical and electrocatalytic characterizations of the constructed electro-catalysts were appraised by scanning electron microscopy, elemental mapping analysis, FT-IR, XRD, and voltammetry techniques. The superiority of the nanocomposite comprised of all synthesized components, GCE/CuO/ZnFe2O4/rGO, toward electrocatalytic oxidation of CBZ was confirmed. A sensitive oxidation peak was observed for CBZ at 1.2 V in a neutral solution. The LOD was deliberated to be 3 nM with a wide range of linearity in response (0.01 to 90 μM). The easy preparation, high stability, repeatability (RSD % < 3), and good antifouling activity of the GCE modified with the CuO/ZnFe2O4/rGO nano-composite indicated the synergistic effect of zinc ferrite, rGO, and CuO. The applicability of the sensor for CBZ monitoring in human serum and urine species was evaluated with satisfactory results.

Highly efficient activation of peracetic acid by nano-CuO for carbamazepine degradation in wastewater: The significant role of H2O2 and evidence of acetylperoxy radical contribution

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) has attracted increasing attentions towards contaminant degradation in the wastewater treatment. Herein, we report the efficient activation of PAA by nano-CuO (nCuO/PAA) to degrade carbamazepine (CBZ) for the first time. Rapid degradation of CBZ was observed in the nCuO/PAA system at neutral initial pH. A new scavenging experiment with Mn2+ as a specific scavenger was developed to distinguish the dominant role of CH3C(O)OO● for CBZ degradation in the nCuO/PAA process. The oxidation of CBZ by CH3C(O)OO● was verified to proceed via the electrons transfer, and the acute and chronic toxicity of the transformation products was significantly reduced. The efficient activation of PAA by nCuO was found to be realized through continuous conversion of Cu(II) to Cu(I), which was significantly boosted by co-existing H2O2. The nCuO/PAA process was slightly affected by the water matrices, and maintained high efficiency in real water samples. The findings obtained in this study provide new insights into the catalytic formation of CH3C(O)OO● from PAA and facilitate the development and application of PAA-based AOPs in wastewater treatment.

Insights into bromate reduction by Fe(II): Multiple radicals generation and carbamazepine oxidation

• Reduction of BrO 3 − by Fe(II) produced HO•, O 2 • − and reactive bromine species. • HO• and O 2 • − were generated from decomposition of BrO 3 − and its intermediates. • BrO 3 − /Fe(II) system can efficiently degrade organics with diverse structures. • Degradation products of carbamazepine were identified in BrO 3 − /Fe(II) system. • Effect of reaction conditions and water matrices was studied. Reduction of bromate (BrO 3 − ) by various technologies has been extensively investigated, while the fate of oxygen and bromine atoms in BrO 3 − in these processes has been largely ignored. In this study, reduction of BrO 3 − by Fe(II) ions was investigated under various conditions via electron spin resonance (ESR), laser flash photolysis (LFP), probe of phenol and quenching experiments. It was found that reduction of BrO 3 − by Fe(II) ions produced HO•, O 2 • − and reactive bromine species (eg., Br• and Br 2 • − ). HO• and O 2 • − were generated from release of one/two oxygen atoms in BrO 3 − and its reduction intermediates (BrO 2 − and BrO − ) at one time, while Br• and Br 2 • − were generated from activation of hypobromous acid by Fe(II) and reactions of HO• with formed Br − . Due to the formation of these reactive species, the tested ten organic pollutants with diverse structures can be efficiently degraded, which including carbamazepine (CBZ), ibuprofen, phenol, benzoic acid, paracetamol, bisphenol a, 4-chlorophenol, oxcarbazepine, diclofenac and sulfamethoxazole. CBZ degradation intermediates by BrO 3 − /Fe(II) system were specially identified by liquid chromatography (LC)-mass spectrometry (MS), and three pathways of hydroxylation/nitrosylation, ring contraction-amine cleavage and bromination for CBZ degradation were proposed accordingly. This study might shed new fundamental insights to bromate reduction and its implication for transformation of co-existed organic pollutants.

Efficient degradation of carbamazepine in a neutral sonochemical FeS/persulfate system based on the enhanced heterogeneous-homogeneous sulfur-iron cycle

In this study, a novel ultrasound enhanced FeS/persulfate Fenton-like system (US/FeS/PDS) was developed for the synergistic degradation of a typical drug carbamazepine (CBZ) under neutral circumstances. Factors such as FeS dosage, PDS dosage, initial pH and temperature, as well as coexisting anions were investigated. High dosages of FeS and PDS, elevated temperature and acidic circumstances were favorable for the oxidation of CBZ. Presence of HCO3− strongly inhibited the CBZ degradation in the US/FeS/PDS system, while slight suppression was observed with either NO3− or Cl−. Seven intermediates were identified as the products from the decomposition of CBZ by hydroxyl radicals (OH·) and sulfate radicals (SO4−·). Time-dependent radical examination indicated that homogeneous OH· and SO4−· would contribute to the CBZ removal from 22.6 to 34.7% and 12.9 to 50.5%, respectively, while the contribution of solid-liquid interfacial radicals decreased from 64.5 to 20.2%. Meanwhile, the oxidation of S2− occurred concurrently with reduction of Fe(III) to Fe(II). The reaction mechanism in the US/FeS/PDS system was proposed based on the sonochemical heterogeneous-homogeneous sulfur-iron cycle in the US/FeS/PDS system. US would firstly enhance the interfacial sulfur-iron electron transfer and the disintegration of the passivation layer, and then lead to the overall improvement in both interfacial and bulk sulfur-iron cycle, as well as the degradation of CBZ.