Degradation of carbamazepine by vacuum-UV oxidation process: Kinetics modeling and energy efficiency.

Vaccum-ultraviolet (VUV) is effective for elimination of organic contaminants in aqueous environment and degradation of carbamazepine (CBZ) by VUV irradiation was systematically investigated in this study. A dynamic kinetic model was developed to simulate the destruction of CBZ that is mainly initiated by hydroxyl radicals (HO). The second-order rate constant of the reaction between CBZ and HO was determined to be 1.4 × 109 M-1 s-1. Effect of initial CBZ concentration, VUV irradiation intensity and natural organic matter (NOM) were further investigated in several batch experiments. The predicted CBZ removal rates increased with the increasing VUV intensity, while decreased with the increasing initial CBZ and NOM concentrations. Based on the electrical energy per order (EE/O) calculation, the optimal VUV intensity was determined to be 7.5 × 10-8 Einstein s-1. Meanwhile, several intermediates/products were identified and their time-dependent evolution profiles were determined, and finally a plausible degradation pathway of CBZ was proposed. Ecotoxicity assessment indicated that the potential toxicity of CBZ and its oxidation products should be paid more attention in the VUV process.

Oxidative removal of carbamazepine by peroxymonosulfate (PMS) combined to ionizing radiation: Degradation, mineralization and biological toxicity.

Carbamazepine is one of pharmaceutical and personal care products (PPCPs) and has been widely used to treat depression and seizures, and it cannot be effectively removed during the conventional wastewater treatment processes. In this study, three processes were used for the carbamazepine degradation, including single radiation, radiation in the presence of peroxymonosulfate (PMS) and radiation followed by PMS oxidation. The results show that radiation in the presence of PMS could enhance the degradation and mineralization of carbamazepine, decreasing the absorbed dose required for completely degrading carbamazepine from 800 Gy to 300 Gy, no matter what the molar ratio of PMS to carbamazepine was. The radiation followed by PMS oxidation significantly increased the mineralization, and the maximum mineralization achieved 46.5% at the dose of 600 Gy. Eight intermediates were tentatively identified. Compared to single radiation process, the radiation in the presence of PMS enhanced the transformation of intermediates and the release of ammonium ion. In real wastewater, the radiation in the presence of PMS could effectively remove carbamazepine and considerably decreased the biological toxicity of the wastewater containing carbamazepine.

Low levels of iron enhance UV/H2O2 efficiency at neutral pH.

While the presence of iron is generally not seen as favorable for UV-based treatment systems due to lamp fouling and decreased UV transmittance, we show that low levels of iron can lead to improvements in the abatement of chemicals in the UV-hydrogen peroxide advanced oxidation process. The oxidation potential of an iron-assisted UV/H2O2 (UV254 + H2O2 + iron) process was evaluated at neutral pH using iron levels below USEPA secondary drinking water standards (<0.3 mg/L). Para-chlorobenzoic acid (pCBA) was used as a hydroxyl radical (HO) probe to quantify HO steady state concentrations. Compounds degraded by different mechanisms including, carbamazepine (CBZ, HO oxidation) and N-nitrosodimethylamine (NDMA, direct photolysis), were used to investigate the effect of iron on compound degradation for UV/H2O2 systems. The effects of iron species (Fe2+ and Fe3+), iron concentration (0-0.3 mg/L), H2O2 concentration (0-10 mg/L) and background water matrix (low-carbon tap (LCT) and well water) on HO production and compound removal were examined. Iron-assisted UV/H2O2 efficiency was most influenced by the target chemical and the water matrix. Added iron to UV/H2O2 was shown to increase the steady-state HO concentration by approximately 25% in all well water scenarios. While CBZ removal was unchanged by iron addition, 0.3 mg/L iron improved NDMA removal rates in both LCT and well water matrices by 15.1% and 4.6% respectively. Furthermore, the combination of UV/Fe without H2O2 was also shown to enhance NDMA removal when compared to UV photolysis alone indicating the presence of degradation pathways other than HO oxidation.

Comparison of the toxicological impacts of carbamazepine and a mixture of its photodegradation products in Scrobicularia plana.

In the aquatic environment, pharmaceutical drugs are submitted to degradation processes, where photodegradation is one of the most important mechanisms affecting the fate, persistence and toxicity of the compounds. Carbamazepine, a widely used antiepileptic, is known to suffer photodegradation in water bodies and generate photoproducts, some of them with higher potential toxicity than the parent compound. Therefore, to evaluate the toxic effects of CBZ when combined with its photoproducts, an acute exposure (96h) with the edible clam Scrobicularia plana was performed using environmental concentrations of CBZ (0.00-9.00µg/L) irradiated (and non-irradiated) with simulated solar radiation. The analysis of the irradiated CBZ solutions by mass spectrometry revealed the formation of 5 photoproducts, including acridine (a compound known to be carcinogenic). Oxidative stress results showed that the exposure to CBZ photoproducts did not increase the toxicity to clams, by comparison with the parent compound. Lipid peroxidation levels, catalase and superoxide dismutase activities were the most responsive parameters to these stressors and lipid peroxidation results appeared to show the presence of an antagonistic effect resulting from the mixture of CBZ and its photoproducts.

Carbamazepine degradation by gamma irradiation coupled to biological treatment.

Carbamazepine is an emerging contaminant and resistant to biodegradation, which cannot be effectively removed by the conventional biological wastewater treatment processes. In this study, the combined gamma irradiation and biodegradation was employed to remove carbamazepine from wastewater. The effect of dose on the removal of carbamazepine was studied at different doses (300, 600 and 800Gy). The results showed that the removal efficiency of carbamazepine increased with dose increasing during the irradiation process. The maximum removal efficiency was 99.8% at 800Gy, while the removal efficiency of total organic carbon (TOC) was only 26.5%. The removal efficiency of TOC increased to 79.3% after the sequent biological treatment. In addition, several intermediates and organic acids were detected. The possible degradation pathway of carbamazepine during the integrated irradiation and biodegradation was proposed. Based on the overall analysis, the combined gamma irradiation and biological treatment process can be an alternative for removing the recalcitrant organic pollutants such as carbamazepine from wastewater.

Response surface modeling of Carbamazepine (CBZ) removal by Graphene-P25 nanocomposites/UVA process using central composite design.

Graphene-P25 (Gr-P25) nanocomposites were synthesized by a simple microwave hydrothermal method. The nanocomposites with different graphene loading were evaluated for the degradation of an important pharmaceutical water pollutant, Carbamazepine (CBZ) under UVA irradiation in a batch reactor. Response surface methodology (RSM) was used to optimize three key independent operating parameters, namely Gr-P25 nanocomposites dose (X1), CBZ initial concentration (X2) and UV light intensity (X3), for photocatalytic degradation of CBZ. The central composite design (CCD) consisting of 20 experiments determined by 2(3) full factorial designs with six axial points and six center points was used to conduct experiments. The results showed that CBZ removal was significantly affected by the synergistic effect of linear term of Gr-P25 dose (X1) and UV intensity (X3). However, the quadratic terms of Gr-P25 (X1(2)) and UV intensity (X3(2)) had an antagonistic effect on CBZ removal. The obtained RSM model (R(2) = 0.9206) showed a satisfactory correlation between experimental and predicted values of CBZ removal. The optimized conditions for achieving 100% CBZ removal with 5 min UVA irradiation were 25.14 mg/L, 167.68 ppb and 1.35 mW/cm(2) for Gr-P25 dose, initial concentration of CBZ and UV intensity, respectively.

Removal of emerging contaminants by simultaneous application of membrane ultrafiltration, activated carbon adsorption, and ultrasound irradiation.

Advanced wastewater treatment is necessary to effectively remove emerging contaminants (ECs) with chronic toxicity, endocrine disrupting effects, and the capability to induce the proliferation of highly resistant microbial strains in the environment from before wastewater disposal or reuse. This paper investigates the efficiency of a novel hybrid process that applies membrane ultrafiltration, activated carbon adsorption, and ultrasound irradiation simultaneously to remove ECs. Diclofenac, carbamazepine, and amoxicillin are chosen for this investigation because of their assessed significant environmental risks. Removal mechanisms and enhancement effects are analysed in single and combined processes. The influence of adsorbent dose and ultrasonic frequency to EC removal are also investigated. Results suggest that adsorption is probably the main removal mechanism and is affected by the nature of ECs and the presence of other components in the mixture. Almost complete removals are achieved in the hybrid process for all ECs.

Phototransformation of wastewater-derived trace organic contaminants in open-water unit process treatment wetlands.

Open-water cells in unit process treatment wetlands can be used to exploit sunlight photolysis to remove trace organic contaminants from municipal wastewater effluent. To assess the performance of these novel systems, a photochemical model was calibrated using measured photolysis rates for atenolol, carbamazepine, propranolol, and sulfamethoxazole in wetland water under representative conditions. Contaminant transformation by hydroxyl radical ((•)OH) and carbonate radical ((•)CO3(-)) were predicted from steady-state radical concentrations measured at pH values between 8 and 10. Direct photolysis rates and the effects of light screening by dissolved organic matter on photolysis rates were estimated using solar irradiance data, contaminant quantum yields, and light screening factors. The model was applied to predict the land area required for 90% removal of a suite of wastewater-derived organic contaminants by sunlight-induced reactions under a variety of conditions. Results suggest that during summer, open-water cells that receive a million gallons of water per day (i.e., about 4.4 × 10(-2) m(3) s(-1)) of nitrified wastewater effluent can achieve 90% removal of most compounds in an area of about 15 ha. Transformation rates were strongly affected by pH, with some compounds exhibiting faster transformation rates under the high pH conditions associated with photosynthetic algae at the sediment-water interface and other contaminants exhibiting faster transformation rates at the circumneutral pH values characteristic of algae-free cells. Lower dissolved organic carbon concentrations typically resulted in increased transformation rates.

Impact of water quality on removal of carbamazepine in natural waters by N-doped TiO2 photo-catalytic thin film surfaces.

Photocatalytic experiments on the pharmaceutical pollutant carbamazepine (CBZ) were conducted using sol-gel nitrogen-doped TiO(2)-coated glass slides under a solar simulator. CBZ was stable to photodegradation under direct solar irradiation. No CBZ sorption to the catalyst surface was observed, as further confirmed by surface characterization using X-ray photoelectron spectroscopic analysis of N-doped TiO(2) surfaces. When exposing the catalyst surface to natural organic matter (NOM), an excess amount of carbon was detected relative to controls, which is consistent with NOM remaining on the catalyst surface. The catalyst surface charge was negative at pH values from 4 to 10 and decreased with increasing pH, correlated with enhanced CBZ removal with increasing medium pH in the range of 5-9. A dissolved organic carbon concentration of 5mg/L resulted in ~20% reduction in CBZ removal, probably due to competitive inhibition of the photocatalytic degradation of CBZ. At alkalinity values corresponding to CaCO(3) addition at 100mg/L, an over 40% decrease in CBZ removal was observed. A 35% reduction in CBZ occurred in the presence of surface water compared to complete suppression of the photocatalytic process in wastewater effluent.

Fate of selected pharmaceuticals in river waters.

The aqueous environmental fate of two antibiotics, lincomycin and clarithromycin, and an antiepileptic drug, carbamazepine, was investigated by monitoring drugs decomposition and identifying intermediates in Po river water (North Italy). Initially, control experiments in the dark and under illumination were performed on river water spiked with drugs to simulate all possible transformation processes occurring in the aquatic system. Under illumination, these pharmaceuticals were degraded and transformed into numerous organic intermediate compounds. Several species were formed and characterised by analysing MS and MS(n) spectra and by comparison with parent molecule fragmentation pathways. River water was sampled at three sampling points in an urban area. The selected pharmaceuticals were detected in all samples. Eight transformation products identified in the laboratory simulation were found in natural river water from carbamazepine degradation, three from clarithromycin and two from lincomycin. Their transformation occurring in aquatic system mainly involved mono- and poly-hydroxylation followed by oxidation of the hydroxyl groups.

Comparative study of the degradation of carbamazepine in water by advanced oxidation processes.

Degradation of carbamazepine (CBZ) using ultraviolet (UV), UV/H2O2, Fenton, UV/Fenton and photocatalytic oxidation with TiO2 (UV/TiO2) was studied in deionized water. The five different oxidation processes were compared for the removal kinetics of CBZ. The results showed that all the processes followed pseudo-first-order kinetics. The direct photolysis (UV alone) was found to be less effective than UV/H2O2 oxidation for the degradation of CBZ. An approximate 20% increase in the CBZ removal efficiency occurred with the UV/Fenton reaction as compared with the Fenton oxidation. In the UV/TiO2 system, the kinetics of CBZ degradation in the presence of different concentrations of TiO2 followed the pseudo-first order degradation, which was consistent with the Langmuir-Hinshelwood (L-H) model. On a time basis, the degradation efficiencies ofCBZ were in the following order: UV/Fenton (86.9% +/- 1.7%) > UV/TiO2 (70.4% +/- 4.2%) > Fenton (67.8% +/- 2.6%) > UV/H2O2 (40.65 +/- 5.1%) > UV (12.2% +/- 1.4%). However, the lowest cost was obtained with the Fenton process.

Enhanced biodegradation of carbamazepine after UV/H2O2 advanced oxidation.

Carbamazepine is one of the most persistent pharmaceutical compounds in wastewater effluents due to its resistance to biodegradation-based conventional treatment. Advanced oxidation can efficiently degrade carbamazepine, but the toxicity and persistence of the oxidation products may be more relevant than the parent. This study sets out to determine whether the products of advanced oxidation of carbamazepine can be biotransformed and ultimately mineralized by developing a novel methodology to assess these sequential treatment processes. The methodology traces the transformation products of the (14)C-labeled carbamazepine during UV/hydrogen peroxide advanced oxidation and subsequent biotransformation by mixed, undefined cultures using liquid scintillation counting and liquid chromatography with radioactivity, mass spectrometry, and UV detectors. The results show that the oxidation byproducts of carbamazepine containing a hydroxyl or carbonyl group can be fully mineralized by a mixed bacterial inoculum. A tertiary treatment approach that includes oxidation and biotransformation has the potential to synergistically mineralize persistent pharmaceutical compounds in wastewater treatment plant effluents. The methodology developed for this study can be applied to assess the mineralization potential of other persistent organic contaminants.

Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation.

The application of sonolysis (US) for remediation of wastewater is an area of increasing interest. The aim of this study was to evaluate the ultrasonic (US) process on the degradation of pharmaceuticals (diclofenac (DCF), amoxicillin (AMX), carbamazepine (CBZ)) in single solutions and also in three mixtures spiked in urban wastewater effluent. Several operating conditions, such as power density (25-100 W L(-1)), initial substrate concentrations (2.5-10 mg L(-1)), initial solution pH (3-11), and air sparging were varied for the evaluation and understanding of the process. The degradation (as assessed by measuring UV absorbance), the generation of hydroxyl radicals (as assessed measuring H(2)O(2) concentration), the mineralization (in terms of TOC and COD removal), and the aerobic biodegradability (as assessed by the BOD(5)/COD ratio) were monitored during sonication. Ecotoxicity to Daphnia magna, Pseudokirchneriella subcapitata and Lepidium sativum before and after treatment was also evaluated. It was found that the pharmaceuticals conversion is enhanced at increased applied power densities, acidic conditions and in the presence of dissolved air. The reaction rate increases with increasing initial concentration of single pharmaceuticals but it remains constant in the mixtures, indicating different kinetic regimes (i.e. first and zero order respectively). Mineralization is a slow process as reaction by-products are more stable than pharmaceuticals to total oxidation; nonetheless, they are also more readily biodegradable. The toxicity of the wastewater samples before and after contamination with pharmaceuticals both in mixtures and in single substance-containing solutions was observed more severely on P. subcapitata; a fact that raises concerns in regards to the discharge of such effluents. D. magna displayed less sensitivity compared to P. subcapitata because it belongs in a lower taxonomic species than D. magna. The germination index of L. sativum in the presence of the drugs' mixture was stimulated instead of inducing any toxicity effect and this might be attributed to the fact the sample, laden with very low drug concentrations was able to act as a provider of additional nutrient elements.

Photodegradation processes of the antiepileptic drug carbamazepine, relevant to estuarine waters.

The photodegradation of carbamazepine was studied in artificial estuarine water, under conditions relevant to the Rhône delta. Chloride substantially enhances the photodegradation of carbamazepine, most likely because of the interaction between Fe(III) colloids and Cl- ions under irradiation, yielding Cl2*-. For a given compound, prerequisites for the described degradation enhancement by chloride to be significant are faster degradation via reaction with Cl2*- compared to charge-transfer processes on the surface of Fe(III) colloids and an important role of indirect phototransformation compared to direct photolysis. A major photodegradation intermediate of carbamazepine is acridine, formed by direct photolysis, while hydroxylated/ oxidized compounds are formed in the presence of *OH, and chloroderivative formation is observed in the presence of Fe(III) and chloride.

Photocatalytic degradation of carbamazepine, clofibric acid and iomeprol with P25 and Hombikat UV100 in the presence of natural organic matter (NOM) and other organic water constituents.

The photocatalytic degradation of natural organic matter (NOM) and organic substance mixtures under simulated solar UV light has been investigated with suspended TiO(2). It could be shown by size-exclusion chromatography that photocatalysis of NOM led to a reduction of the average hydrodynamic radii and presumably of the nominal molecular weight, too. The decrease of the UV/Vis absorption of NOM was faster than the NOM mineralization. This study also focuses on the different abilities of photocatalytic materials (P25 and Hombikat UV100) to decrease persistent substances influenced by the presence of NOM and mixtures of pharmaceuticals or diagnostic agents. In general, the presence of NOM and other organic substances retarded the photocatalysis of a specific persistent substance by the combination of radiation attenuation, competition for active sites and surface deactivation of the catalyst by adsorption. The results of this work prove that photocatalysis is a promising technology to reduce persistent substances like NOM, carbamazepine, clofibric acid, iomeprol and iopromide even if they are present in a complex matrix.

Kinetic and chemical assessment of the UV/H2O2 treatment of antiepileptic drug carbamazepine.

The UV/H2O2-induced degradation of carbamazepine, a worldwide used antiepileptic drug, recently found as contaminant in many municipal sewage treatment plant (STP) effluents and other aquatic environments, is investigated. The oxidation treatment caused an effective removal of the drug. At complete abatement of the substrate after 4 min treatment, a 35% value of removed total organic carbon (TOC) was obtained. A kinetic constant of (2.05+/-0.14) x 10(9) lmol(-1)s(-1) was determined for OH radical attack to carbamazepine in the UV/H2O2 process. Preparative TLC of the reaction mixture led to the isolation of acridine-9-carboxaldehyde as a reaction intermediate. HPLC and GC/MS analysis indicated formation of small amounts of acridine, salicylic acid, catechol and anthranilic acid among the reaction products. Under the same reaction conditions, synthetically prepared 10,11-epoxycarbamazepine was easily degraded to acridine as main product, suggesting that this epoxide is a likely intermediate in the oxidative conversion of carbamazepine to acridine. Under sunlight irradiation, carbamazepine in water underwent slow degradation to afford likewise acridine as main product. In view of the mutagenic properties of acridine, these results would raise important issues concerning the possible environmental impact of carbamazepine release through domestic wastewaters and support the importance of prolonged oxidation treatments to ensure complete degradation of aromatic intermediates.

Fate of pharmaceuticals--photodegradation by simulated solar UV-light.

The fate of pharmaceuticals in surface waters under solar irradiation was investigated. Photodegradation of pharmaceuticals caused by sun irradiation may be of major significance in the natural elimination process. Based on a data compilation from the literature, the lipid lowering agent metabolite clofibric acid, the iodinated X-ray contrast media iomeprol, which contribute to the adsorbable organic halogen compounds, and the antiepileptic drug carbamazepine were selected. The irradiation experiments were carried out in batch experiments with simulated UV-sunlight. The photodegradation of the pharmaceuticals showed a pseudo-first-order kinetics. The objective of this investigation was to demonstrate that the extent of photoinduced degradation of pharmaceuticals can vary significantly for the different pharmaceuticals and it strongly depends on the water constituents present in solution. The influences of different initial pharmaceutical concentrations, the presence of other pharmaceuticals like carbamazepine or clofibric acid and the presence of natural organic matter on the photochemical degradation rate of pharmaceuticals in aqueous solutions were investigated. Analyses of the pharmaceuticals and their photodegradation products were carried out by high performance liquid chromatography with diode-array and fluorescence detection.

Pharmaceutical evaluation of carbamazepine modifications: comparative study for photostability of carbamazepine polymorphs by using Fourier-transformed reflection-absorption infrared spectroscopy and colorimetric measurement.

The tablet surface was evaluated without physical damage by means of Fourier-transform infrared reflection-absorption spectroscopy (FT-IR-RAS) and colorimetric measurement (colour difference, delta E) of the carbamazepine polymorphs I, II and III, after photodegradation at two irradiation intensities (3.0 and 12.0 J cm-2s-1) under a near-UV fluorescent lamp. The surface of sample pellets of all crystalline forms turned gradually from white to yellow-orange upon exposure to light, and the discoloration rate of form II was faster than that of forms I and III, indicating that form II was the most unstable of the three. The major photoproducts were identified by HPLC, NMR and MS analyses. The carbamazepine content on the surface of the tablet was determined based on the absorption at 1685 cm-1 attributable to C=O stretch vibration in the FT-IR-RAS spectra before and after irradiation by a near-UV fluorescent lamp. The semilogarithmic plots of the photodegradation profiles of the various polymorphs were straight lines, including the induction period, indicating that degradation of the drug on the surface followed first-order kinetics. The induction periods of all forms were not significantly different. However, the degradation rate constant of form II at 12.0 J cm-2s-1 was 5.1 and 1.5 times larger than those of forms I and III, respectively.