Photodegradation Of Carbamazepine Research Articles

Photodegradation of Carbamazepine and Acridine with 165–200 nm Radiation from a Microcavity-Plasma VUV Phosphor Lamp

Photodegradation of Carbamazepine and Acridine with 165–200 nm Radiation from a Microcavity-Plasma VUV Phosphor Lamp

Elementary Steps in Steady State Kinetic Model Approximation for the Homo-Heterogeneous Photocatalysis of Carbamazepine

Elucidating physicochemical processes in the degradation of pollutants may optimize their removal from water sources. Although the photodegradation of carbamazepine (CBZ) in Advanced Oxidation Processes (AOPs) has been widely studied, there is no detailed report on the elementary steps of the kinetics. This study proposes a set of elementary steps for the AOP of CBZ, combining short-wave ultraviolet radiation (UVC), a homogeneous reagent (H2O2), and a heterogeneous catalyst (TiO2), which includes the excitation of both reagents/catalysts by UVC photons, the adsorption of CBZ by the excited TiO2, or its oxidation by hydroxyl radicals. Assuming the steady-state approximation on the intermediate products (excited TiO2, CBZ-excited TiO2 complex, and hydroxyl radicals) leads to rate laws for the degradation of CBZ, in which UVC radiation, TiO2, and H2O2 are pseudo-first-order at all concentrations or intensities and have no direct influence on CBZ pseudo-order, whereas CBZ shifts from pseudo-first-order at low concentrations to pseudo-zero-order at high concentrations. Several experiments to test the mechanism were conducted by varying CBZ, H2O2, and TiO2 concentrations and UVC radiation intensities. The measured results indeed fit the suggested mechanism for the first three, but the irradiation intensity appears to shift the CBZ influence from pseudo-second- to pseudo-first-order with increased intensities. Part of the elementary steps were changed to fit the results.

Removal of Carbamazepine in Aqueous Solution by TiO2 Ceramic Photo-Catalyst under Simulated Solar Light: Kinetics, Effects of Environmental Factors and Degradation Pathways

Current research on the photocatalytic activity of TiO2 mainly focuses on its nano- or micro-particle forms, which are difficult to recycle and apply in real engineering applications. This study aims to apply a small pilot of TiO2 in the ceramic form to remove carbamazepine (CBZ) from an aqueous solution under simulated sunlight. A high removal efficiency up to >99% was shown in a 5 mg L−1 CBZ solution after 6 h of irradiation with a total energy of 150.92 kJ. The kinetic degradation was not affected in an alkaline solution (at pH 7, pH 10, and pH 13) but was faster under acidic conditions (pH 2) in which CBZ existed in the protonated form. The presence of NO3− (10–50 mg L−1) slightly affected the photodegradation of CBZ while humic acid significantly reduced the photocatalytic activity. In addition, the presence of major ions in water also had a negative effect at concentrations between 10 and 50 mg L−1. The MS/MS was used to identify the transformation products of CBZ, and a possible degradation mechanism was proposed. The toxicity of CBZ and the by-products was primarily evaluated. The results showed that TiO2 ceramics show high reusability and stability with a photocatalytic performance of >95% and a mass loss of <5% after 90 degradation cycles.

A new view on the mechanism of UV photodegradation of the tricyclic antidepressant carbamazepine in aqueous solutions

Mechanism of direct UV photolysis of the tricyclic antidepressant carbamazepine (CBZ) at neutral pH was revealed by a combination of nanosecond laser flash photolysis, steady-state photolysis combined with high resolution LC-MS and DFT quantum-chemical calculations. The detection of short-lived intermediates and the detailed identification of final products were performed for the first time. The quantum yield of CBZ photodegradation (282 nm) is about 0.1% and 0.18% in air-equilibrated and argon-saturated solutions. The primary stage is photoionization with the formation of CBZ cation radical followed by a rapid nucleophilic attack by a solvent molecule. The primary photoproducts are 10-oxo-9-hydro-carbamazepine, 9-formylacridine-10(9H)-carboxamide (a result of ring contraction) and various isomers of hydroxylated CBZ. Prolonged irradiation results to accumulation of acridine derivatives, which should lead to an increase of the toxicity of photolyzed CBZ solutions. The obtained results may be important for understanding the fate of tricyclic antidepressants in processes of UVC disinfection and in natural waters under action of sunlight.

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.

Enhancive and inhibitory effects of copper complexation on triplet dissolved black carbon-sensitized photodegradation of organic micropollutants

Excited-triplet dissolved black carbon (DBC) was deemed as a significant reactive intermediate in the phototransformation of environmental micropollutants, but the impacts of concomitant metal ions on photochemical behavior of excited-triplet DBC (3DBC*) are poorly understood. Here, the photolytic kinetics of sulfadiazine and carbamazepine induced by 3DBC* involving Cu2+ was explored. The presence of Cu2+ reduced the 3DBC*-induced photodegradation rate of sulfadiazine; whereas for carbamazepine, Cu2+ enhanced 3DBC*-induced photodegradation. Cu(II)-DBC complex was formed due to the decreasing fluorescence intensities of DBC in the presence of Cu2+. Cu2+ complexation caused the decrease of 3DBC* steady-state concentrations, which markedly reduced 3DBC*-induced photodegradation rate of sulfadiazine due to its high triplet reactivity. Kinetic model showed that 3DBC* quenching rate by Cu2+ was 7.98 × 109 M−1 s−1. Cu2+ complexation can also enhance the electron transfer ability, thereby producing more ∙OH in Cu(II)-DBC complex, which explains the promoting effect of Cu2+ complexation on carbamazepine photodegradation in view of its low triplet reaction rate. These indicate that 3DBC* reactivity differences of organic micropollutants may explain their photodegradation kinetics differences in DBC system with/without Cu2+, which was supported by the linearized relationship between the photodegradation rate ratios of ten micropollutants with/without Cu2+ and their triplet reaction activity.

Peroxyl radicals from diketones enhanced the indirect photochemical transformation of carbamazepine: Kinetics, mechanisms, and products

In surface waters, photogenerated transients (e.g., hydroxyl radicals, carbonate radicals, singlet oxygen and the triplet states of dissolved organic matter) are known to play a role in the transformation of biorecalcitrant carbamazepine (CBZ). Small diketones, such as acetylacetone (AcAc) and butanedione (BD), are naturally abundant and have been proven to be effective precursors of carbon and oxygen centered radicals. However, the photochemical kinetics and mechanisms of coexisting diketones and CBZ are barely known. Herein, the effects of AcAc and BD on the photochemical conversion of CBZ were investigated compared with H2O2 which was the main ·OH precursor in the environment. An enhancing effect was observed for the degradation of CBZ by the addition of diketones. The enhancing effect of diketones was pH-dependent and much more significant than H2O2 under simulated solar irradiation. On the basis of the identification of transient species and the competition kinetic model, organic peroxyl radicals were found to play a dominant role in CBZ photodegradation, and the second-order rate constants of the reaction between CBZ and peroxyl radicals were determined to be approximately 107–108 M–1s–1. Furthermore, mutagenic acridine was found to be the major cumulative intermediate with a yield of > 30% in the presence of diketones, which might be an environmental concern. This work indicates that the coexistence of diketones and persistent organic pollutants might lead to some detrimental effects on aquatic environments if the water is exposed to sunlight.

Hydrochar-mediated photocatalyst Fe3O4/BiOBr@HC for highly efficient carbamazepine degradation under visible LED light irradiation

• Hydrochar-mediated Fe 3 O 4 /BiOBr@HC was synthesized by a hydrolysis method. • Efficient carbamazepine removal benefited from synergistic effect of Fe 3 O 4 and HC. • Faster charge separation and more active species generation occurred with help of HC. • Active species include superoxide radicals, hydroxyl radicals, and photogenerated holes. • Three degradation pathways were proposed to indirectly verify the role of active species. Construction of composite photocatalysts with high charge transfer efficiency and fast surface catalytic reaction has recently gained huge interest. In this work, a hydrochar microsphere-mediated photocatalyst Fe 3 O 4 /BiOBr@HC with rapid surface catalytic reaction and electron transfer was fabricated. Under visible-LED-light irradiation, removal of refractory analgesic carbamazepine (CBZ) and total organic carbon (TOC) reached 100% and 67.41%, respectively, by Fe 3 O 4 /BiOBr@HC20% within 40 min, demonstrating the excellent photocatalytic activity compared to other photocatalysts. The narrower band gap (2.02 eV) of Fe 3 O 4 /BiOBr@HC obviously improved the visible light absorption. The hydrochar with abundant surface oxygen functional groups provided more active oxygen species ·O 2 – (4.05 µM) and ·OH (107.8 nM), and acted as an electron bridge to promote the electron transfer of BiOBr and Fe 3 O 4 . Eleven main CBZ intermediates were identified and three degradation pathways were proposed to illustrate the contribution of superoxide radicals, hydroxyl radicals, and photogenerated holes to the photodegradation of CBZ. Furthermore, five-cycle reusing experiments revealed that Fe 3 O 4 /BiOBr@HC composite catalysts have excellent reusability and stability, indicating that they have a promising application future.

Photocatalytic Degradation of Organic Micropollutants in Water by Zr-MOF/GO Composites

Nanocomposites of UiO-66 and graphene oxide (UiO-66_GO) were prepared with different GO contents by a one-step hydrothermal method, and their photocatalytic activities for the degradation of carbamazepine (CBZ) were investigated under ranges of GO loading, catalyst dose, initial pollutant concentration, and solution pH. The UiO-66_GO nanocomposites showed photocatalytic rate constant up to 0.0136 min−1 for CBZ degradation and its high overall removal efficiency (>90%) in 2 h. The photocatalytic rate constant over the UiO-66_GO nanocomposite was about 2.8 and 1.7 times higher than those over pristine GO and UiO-66, respectively. The enhancement of photocatalytic activity by GO was attributed to increased surface area and porosity, improved light absorption, and narrowed band gap. The composite also showed substantial recyclability and stability over five consecutive cycles of photocatalytic degradation. The experimental results indicated that O2●− and OH● are the responsible radicals for photocatalytic degradation, which helped us propose a photocatalytic mechanism for the enhanced CBZ photodegradation. This work provides a reference for the development of GO-based composite photocatalysts and expands the application of UiO-66 as a photocatalyst for the degradation of persistent micropollutants in water.

Solar photodegradation of carbamazepine from aqueous solutions using a compound parabolic concentrator equipped with a sun tracking system

AbstractThe primary purpose of this study was to investigate the efficiency of a Compound Parabolic Concentrator (CPC) equipped with a sun tracking system in the photolysis of carbamazepine as a refractory organic compound. The natural sunlight experiments were accomplished during the period May–July 2017 in Tehran, Iran. The intermediate by-products of the process of solar photodegradation of carbamazepine (CBZ) were characterized using LC–MS. The results showed that increasing the reactor temperature did not significantly change CBZ degradation efficiency. However, the solution pH played a comparatively important role in CBZ solar photo degradation: removal efficiency increased considerably with pH from about 49% at pH 7 to almost 61% at pH 9. According to our findings, using a CPC reactor equipped with a sun tracker system promotes the solar photo-transformation rate of CBZ by 2-3 fold. In addition, LC/MS analysis showed that eight main intermediates were formed in the treated solution after solar photodegradation of CBZ. Therefore, complete mineralization of CBZ was not accomplished.

Fe(III)-citrate enhanced sunlight-driven photocatalysis of aqueous Carbamazepine

We investigated the effect of Fe(III)-citrate complexes on the photodegradation of Carbamazepine (CBZ) upon 365 nm irradiation in aqueous solution. A preliminary study of a {CBZ/Fe(III)-citrate} mixture in the dark and at room temperature showed no evidence of reaction. CBZ degradation efficiency depends on the pH of the medium, an effect attributed mainly to the speciation of Fe(III)-citrate. The influence of [CBZ] or [Fe(III)-citrate] on the kinetics of the reaction was studied. The reaction is biphasic, the first stage ends after ca. fifteen minutes and accounts for the major percentage of degradation. The presence of Fe(III)-citrate complex largely enhances the formation of Fe2+ and HO radicals; they form at the same rate at the beginning of the reaction. Increasing [O2] improved the degradation rate, and the use of i-PrOH as a scavenger confirmed the participation of HO in CBZ photodegradation. CBZ photodegradation was also studied under natural sunlight showing a degradation only slightly lower than under artificial light. HPLC/MS analysis confirmed 11% yield epoxycarbamazepine as the only reaction product observable with this technique after 180 min irradiation. An appropriate mechanism is proposed for CBZ transformation. CBZ phototransformation reached 65% at pH = 6.24, 87% at pH = 4.30 and ca. 100% at pH = 2.86 after 180 min upon 365 nm irradiation and the mineralization efficiency reaches 70% of TOC removal after 6 h of treatment. Our evidences show the epoxide photoproduct is just an intermediate that further reacts towards mineralization. This work highlights the important role of Fe(III)-carboxylate complexes may have on the fate of persistent organic pollutants in aquatic environments when irradiated with UV-A light.

Insight into enhanced carbamazepine photodegradation over biochar-based magnetic photocatalyst Fe3O4/BiOBr/BC under visible LED light irradiation

A novel, economical and magnetically separable heterojunction photocatalyst Fe3O4/BiOBr stacked on reed straw biochar (Fe3O4/BiOBr/BC) with visible light response was successfully prepared via a facile modified one-step hydrolysis method for the first time. The target pollutant carbamazepine (CBZ) was used to further investigate the photocatalytic activity of Fe3O4/BiOBr/BC. Compared with BiOBr and Fe3O4/BiOBr, novel photocatalyst Fe3O4/BiOBr/BC owing to the introduction of biochar exhibited better photocatalytic activity (95.51%) of CBZ photodegradation even under 50 W energy-saving visible LED light irradiation. Additionally, effect of pH on CBZ photodegradation using Fe3O4/BiOBr/BC was insignificant meaning wider practical application. Besides, three common anions (Cl−, NO3−, SO42−) and DOM existing in natural water exhibited beneficial or detrimental effects to some extent. Free radicals trapping experiments results illustrated high carbamazepine removal efficiency could be ascribed to superoxide radicals and hydroxyl radicals. The transformation intermediates of CBZ were determined by HRMS and the possible photodegradation pathways were proposed. Finally, good reusability and stability verified the excellent practicality and feasibility of Fe3O4/BiOBr/BC for removal of organic pollutants in aqueous.

Assembly of graphene on Ag3PO4/AgI for effective degradation of carbamazepine under Visible-light irradiation: Mechanism and degradation pathways

A highly efficient visible-light-driven photocatalyst Ag3PO4/AgI-Graphene (Ag3PO4/AgI-G) was synthesized through a chemical coprecipitation procedure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were performed to study the physicochemical structural of the photocatalysts. The photocatalytic activity of the samples was examined by the carbamazepine (CBZ) degradation under artificial visible light and natural sunlight irradiation. Experimental results indicated that the introduction of low mass content of graphene enhanced the photocatalytic performance of Ag3PO4/AgI, and the photocatalytic degradation efficiency of CBZ over Ag3PO4/AgI-3%G (mass ratio of graphene:Ag3PO4/AgI = 3:100) reached 93.06% within 21 min, which was much higher than that over pure Ag3PO4 (26.92%) and Ag3PO4/AgI (74.38%). UV–vis diffuse reflectance spectra, photoluminescence (PL) spectra, transient photocurrent responses and electrochemical impedance spectra (EIS) of the samples were conducted to verify the high photocatalytic performance of the Ag3PO4/AgI-3%G. In addition, possible photocatalytic degradation pathways of CBZ were proposed based on the analysis of transformation products during the reaction. The reactive species trapping experiments and Electron spin resonance (ESR) analysis demonstrated that h+ and O2− were the main active oxidant species responsible for CBZ photodegradation. The photocatalytic degradation mechanism of CBZ over Ag3PO4/AgI-3%G under visible light irradiation was schematically proposed. This study not only provides a new technique for the synthesis of Ag3PO4-based photocatalysts with high photocatalytic activity, but also demonstrates that the Ag3PO4/AgI-3%G composite could be a promising photocatalyst for the treatment of waters containing CBZ.

Surprise in the phosphate modification of BiOCl with oxygen vacancy: In situ construction of hierarchical Z-scheme BiOCl-OV-BiPO4 photocatalyst for the degradation of carbamazepine

Phosphate modification is a general strategy for improving the photocatalytic activities of semiconductors. Ion exchange can be occurred during the phosphate modification process. This would give a surprise for a new phase formed on the surface of the parent photocatalyst. More importantly, this is conductive to form close contact and continuous interface favoring the charge transfer between two phases. Here, a novel BiOCl-OV-BiPO4 photocatalyst was fabricated using a facile in situ phosphate modification method. BiOCl-OV-BiPO4 displayed a maximum carbamazepine (CBZ) degradation efficiency of 81.70% after 30 min Xe lamp irradiation, with a reaction kinetics rate constant (k) of 5.75 times higher than ordinary BiOCl samples. Oxygen vacancy (OV) is important for the construction of Z-scheme BiOCl-OV-BiPO4: OV benefits the generation of BiPO4 on the surface of BiOCl; furthermore, OV acting as electron mediator, promotes the separation of photogenerated charge carriers between BiOCl and BiPO4. Based on the results from PL tests, photocurrent density, EIS Nyquist plots, and cyclic voltammetry, it can be demonstrated that Z-scheme structure of BiOCl-OV-BiPO4 not only increases the photogenerated electrons-holes separation rate but also retains their strong redox ability. This significantly facilitates the production of superoxide radical (O2−) and holes (h+), which dominates the CBZ photodegradation. This work provides a new sight for the fabrication of Z-scheme photocatalysts to improve the photocatalytic performance.

Photodegradation of carbamazepine with BiOCl/Fe3O4 catalyst under simulated solar light irradiation

A magnetic BiOCl/Fe3O4 catalyst with simulated solar light response was successfully prepared through a precipitation process and characterized by X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, VSM, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy. The photocatalytic activity of BiOCl/Fe3O4 nanocomposites was further investigated through the photodegradation efficiency of carbamazepine (CBZ). In this study, 90.3% of CBZ was removed after 60min irradiation in the presence of the BiOCl/Fe3O4 catalyst. Three reactive species were identified; the contribution of h+, HO, and O2- to CBZ degradation was approximately 94.98%, 3.25%, and 1.06%, respectively. The pH value had a significant effect on the CBZ degradation, and the best performance was achieved at pH 2.68. The presence of common anions (NO3−, Cl−, CO32−, and SO42−) also affected the CBZ degradation. The inhibiting effect followed the order of CO32−>SO42−>Cl−. However, NO3− weakly favored the photodegradation of CBZ. Moreover, the BiOCl/Fe3O4 photocatalyst could be easily recollected from the solution by applying an external magnetic field. This type of magnetic photocatalyst, which is characterized by ease of separation, may have application potential in wastewater treatment. The disappearance of CBZ as well as the formation of its products were determined by liquid chromatography mass spectroscopy and the possible photocatalytic degradation pathways were proposed.

Substrate-immobilized electrospun TiO2 nanofibers for photocatalytic degradation of pharmaceuticals: The effects of pH and dissolved organic matter characteristics

A substrate-immobilized (SI) TiO2 nanofiber (NF) photocatalyst for multiple uses was prepared through electrospinning and hot pressing. The rate of furfuryl alcohol degradation under UV irradiation was found to be the highest when the anatase to rutile ratio was 70:30; the rate did not linearly increase as a function of the NF film thickness, mainly due to diffusion limitation. Even after eight repeated cycles, it showed only a marginal reduction in the photocatalytic activity for the degradation of cimetidine. The effects of pH and different organic matter characteristics on the photodegradation of cimetidine (CMT), propranolol (PRP), and carbamazepine (CBZ) were investigated. The pH-dependence of the photocatalytic degradation rates of PRP was explained by electrostatic interactions between the selected compounds and the surface of TiO2 NFs. The degradation rates of CMT showed the following order: deionized water > l-tyrosine > secondary wastewater effluent (effluent organic matter) > Suwannee River natural organic matter, demonstrating that the characteristics of the dissolved organic matter (DOM) can affect the photodegradation of CMT. Photodegradation of CBZ was affected by the presence of DOM, and no significant change was observed between different DOM characteristics. These findings suggest that the removal of CMT, PRP, and CBZ during photocatalytic oxidation using SI TiO2 NFs is affected by the presence of DOM and/or pH, which should be importantly considered for practical applications.

Photo-degradation of carbamazepine using TiO2 suspended photocatalysts

Carbamazepine (CBZ), a persistent pharmaceutical compound, cannot be effectively removed (<10%) by conventional wastewater treatment plants. This study investigates the removal of this molecule in water solution using a photocatalytic process at 365 nm. Five commercial TiO2-based photocatalysts (P90, P25, UV100, PC500, and ST01) were tested over a range of operating parameters (type and concentration of photocatalysts, pH, treatment time, and light intensity). The best operating conditions for CBZ degradation in solution (99% CBZ removal) were obtained using P90 as photocatalyst at a concentration of 1.5 g/L for 90 min of treatment with a pH of 5.0 and a light intensity of 18.9 W/m2. Under these conditions, removal of 74% of total organic carbon was recorded. This optimized photocatalytic process can treat either relatively high concentrations of CBZ (5 mg/L to 20 mg/L) or low concentrations of CBZ (37 µg/L) in water. The initial rate of photocatalytic degradation of CBZ using P90 as photocatalyst can be described by the Langmuir–Hinshelwood (L–H) kinetic model with a reaction rate constant of 2.22 ± 0.003 mg/L/min at ca. 20 °C.

Aquatic photolysis of carbamazepine by UV/H2O2 and UV/Fe(II) processes

In this work, the degradation of carbamazepine (CBZ) in water by UV/H2O2 and UV/Fe(II), two UV-based photolysis processes, was investigated. The addition of H2O2 and Fe(II) significantly improved the CBZ decomposition rate relevant to UV treatment alone. For UV/H2O2 photolysis, CBZ photodegradation followed pseudo-first-order kinetics. The rate of CBZ degradation increased with the increase of H2O2 concentrations and the decrease of initial CBZ concentrations. CBZ oxidation rates in sea water and surface water were lower than that in pure water and the maximum CBZ degradation occurred at pH 7. Additionally, both Cl− and HCO3 − could inhibit the CBZ decomposition in UV/H2O2 photolysis. For the UV/Fe(II) system, CBZ photodegradation also showed pseudo-first-order kinetics. The results showed that the degradation increased as the initial Fe(II) concentration increased up to a certain limit at which Fe(II) reduced the degradation by scavenging the $$\cdot {\text{OH}}$$ . O2 was favorable for CBZ degradation in UV/Fe(II) process. Finally, major degradation products of CBZ, including degradation intermediates, organic acids, and inorganic ions were detected by LC/MS/MS and IC. Based on the LC/MS/MS and IC analysis, the possible degradation pathways of CBZ photolysis were proposed. Results demonstrated that UV/H2O2 and UV/Fe(II) were both potential technologies for water treatment containing CBZ. However, considering the energy consumption, UV/Fe(II) was more efficient than UV/H2O2 process for CBZ degradation.

Photocatalytic degradation of carbamazepine and three derivatives using TiO2 and ZnO: Effect of pH, ionic strength, and natural organic matter

Removal of pharmaceuticals (PhCs) by photocatalysis is a promising avenue in water treatment. The efficiency of these treatments on PhC derivatives compared to their parent molecules remains poorly documented. The present study investigates the efficiency of photodegradation catalyzed by TiO2 and ZnO nanoparticles on the removal of carbamazepine (CBZ) and three of its derivatives; carbamazepine epoxide (CBZ-E), acridine (AI), and acridone (AO). The effects of environmental parameters such as pH, ionic strength, and natural organic matter content on photodegradation efficiency (transformation after 6h and kinetics) were tested. We report that the efficiency of the catalysts (TiO2 and ZnO) can be very different when comparing CBZ and its derivatives (CBZ-E, AI and AO). TiO2 was more efficient than ZnO at degrading CBZ and CBZ-E. For AI and AO, no significant differences were observed between the two catalysts. We also report that environmental parameters have contrasting effects on the efficiency of the photodegradation of CBZ compared to its derivatives. Changing pH and organic matter content had the most contrasted effects; the photodegradation of CBZ and CBZ-E was significantly affected by pH (especially in presence of TiO2 NPs) and by the presence of natural organic matter. In contrast, the photodegradation of AI and AO was not affected by pH and organic matter. Only the photodegradation of CBZ was clearly affected by IS and solely at very high IS (1M). Overall, our results highlight that TiO2 and ZnO catalysts present contrasted efficiency on the removal of CBZ when compared to its derivatives (CBZ-E, AI and AO). Our results also show that the effect of environmental parameters on the efficiency of the photodegradation of CBZ derivatives cannot be predicted based on the behavior of the parent molecule (CBZ).

Evaluating the photodegradation of Carbamazepine in a sequential batch photoreactor system: Impacts of effluent organic matter and inorganic ions

Removal of pharmaceutical Carbamazepine (CBZ) compound from municipal wastewater has become an issue from the human health and environmental risks point of view, due to its latent recalcitrance and toxicity properties. This study investigated the photodegradation performance of a sequential batch annular slurry photoreactor (SB-ASP) system for the removal of CBZ compound from secondary municipal wastewater. Two different immobilised TiO 2 photocatalysts, namely anatase titanate nanofiber and mesoporous TiO 2 impregnated kaolinite catalyst were applied in the SB-ASP system. Various modes of sequential batch reactor (SBR) cycles, presence of effluent organic matter (EOM) and inorganic ions, mainly nitrate and phosphate that could affect the photodegradation performance of the SB-ASP system were evaluated during the removal of CBZ. High performance size exclusion chromatography revealed that the photocatalytic reaction will preferentially compete and attack on high molecular weight EOM prior to the photodegradation of CBZ. The presence of inorganic ions was found to affect the surface fouling of immobilised photocatalysts used to a different extent, without completely retarding their photoactivity. This study also highlighted that the operation of SB-ASP system was useful to enhance the photodegradation of CBZ compound in a semi-continuous operation without constant catalyst replacement. It is foreseeable that the integration of SB-ASP system with biological treatment systems could provide an advanced treatment option for the recycling and reuse of municipal wastewater.