In view of the global concern about the occurrence of taste and odor (T&O) compounds in waters for drinking water supply and the necessity for the development of more innovative and efficient ...technologies for water treatment and depuration, the focus of this study is to provide a state of the art overview on current knowledge for the application of advanced oxidation technologies for the treatment of T&O compounds in aquatic media. The most representative and newly emerging compounds belonging to the major groups of T&O compounds, such as geosmin, methylisoborneol, benzothiazoles, mercaptans and sulfides as well as aromatic and other miscellaneous T&O compounds, are included in the systematic overview. The current data has been compiled and extensively discussed in terms of the degree of degradation, reaction kinetics, effect of operational parameters and water quality, identity of intermediate and final products and possible transformation pathways.
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•The applications of AOPs for the treatment of T&O compounds in water are reviewed.•AOPs exhibited fast kinetics and great degrees of mineralization of T&O compounds.•The main effects of operational parameters and water constituents are discussed.•An overview of the transformation products and reaction mechanisms is provided.•Data gaps and future research needs of AOPs for T&O removal have been assessed.
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•The photocatalytic degradation and mineralization of venlafaxine was studied.•A great number of intermediates were detected by HR-LC–MS.•Ηydroxylation, oxidation, demethylation ...and/or dehydration were the main routes.•Near additive/synergistic toxicity effects between TPs were observed.
The photochemical degradation of the antidepressant drug venlafaxine (VNF) by UV/TiO2 process was investigated in the present study. Prescreening experiments were conducted to study the effects of main parameters affecting the photocatalytic process. In addition, the effects and interactions of most influenced parameters were evaluated and optimized by using a central composite design model and a response surface methodology. Results indicated that VNF was quickly removed in all the irradiation experiments and its degradation was mainly affected by the studied variables (catalyst dose, initial VNF concentration and pH), as well as their interaction effects. Parallel to kinetic studies, the transformation products (TPs) generated during the treatment was investigated using LC coupled to low and high resolution mass spectrometry. Based on identification of the main TPs, tentative transformation pathways were proposed, including hydroxylation, demethylation and dehydration as major transformation routes. Τhe potential risk of VNF and its TPs to aqueous organisms was also investigated using Microtox bioassay before and during the processes. The obtained results showed an increment in the acute toxicity in the first stages and a continuously decreasing after then to very low values reached within 240min of the photocatalytic treatment, demonstrating that UV/TiO2 can lead to the elimination of parent compound and the detoxification of the solution.
In this study, the degradation of Nimesulide (NIM), a non-steroidal anti-inflammatory drug, using photolysis, heterogeneous (TiO2 in dispersion) and homogeneous (photo-Fenton reactant) ...photocatalysis, under simulated solar light (SSL) radiation, was investigated. Various parameters affecting the degradation rate of the target compound during the applied processes were optimized. The efficiency of all treatments used (direct photolysis; TiΟ2/SSL; TiΟ2/Η2Ο2/SSL; TiΟ2/S2Ο82−/SSL; Fe3+/H2O2/SSL; Fe3+/S2O82−/SSL and Fe(C2O4)33−/H2O2/SSL) was evaluated by means of initial reaction rate and mineralization. Moreover, the generated transformation products (TPs) by each basic process (photolysis; TiΟ2/SSL and Fe3+/H2O2/SSL) were identified, using liquid chromatography coupled to high resolution mass spectrometry, and their formation kinetic profiles were given. The main transformation routes of NIM were hydroxylation and fragmentation, for all three treatments applied. Finally, toxicity measurements were conducted using Microtox bioassay in order to evaluate the potential risk of NIM and its TPs to aqueous organisms. Although, the acute toxicity increased during the first stages of treatment the final outcome lead to very low toxicity levels even within 60 min of TiO2/SSL treatment. Concluding, the obtained results suggest that the photocatalytic degradation of NIM can lead to its complete elimination and simultaneously to the detoxification of the solution.
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•NIM is eliminated in less than 45 min, under all photocatalytic treatments.•High percentages of mineralization were achieved by all photocatalytic processes.•Eleven TPs were identified.•Photocatalysis can result in considerable reduction of toxicity towards V. ficheri.
In the present study, the photocatalytic activity of TiO2-based photocatalysts toward degradation and mineralization of the anti-cancer drug 5-fluorouracil (5-FU) in aqueous phase was investigated ...under simulated solar and visible irradiation. Commercial TiO2 (P25) and N/S-doped TiO2 catalysts synthesized by a simple sol–gel method were used as photocatalysts. TiO2 P-25 was found to be the most photoactive catalyst for the removal of 5-FU, under simulated solar irradiation. Among N/S-doped TiO2 catalysts, the one with molar Ti:N/S ratio equal to 0.5 was the most efficient under simulated solar irradiation. In contrast, under visible irradiation the catalyst with equimolar Ti:N/S ratio showed the highest performance for the removal of 5-FU. Scavenging experiments revealed that HO radicals and h+ were the major reactive species mediating photocatalytic degradation of 5-FU using TiO2 P-25 and N/S-doped TiO2 catalysts, under simulated solar irradiation. On the other hand, the essential contribution of 1O2 and O2− in the degradation of 5-FU under visible light was proved. The transformation products (TPs) of 5-FU, were identified by LC-MS-TOF suggesting that defluorination followed by hydroxylation and oxidation are the main transformation pathways, under all the studied photocatalytic systems.
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•Photocatalytic degradation of 5-fluorouracil using TiO2-based photocatalysts was studied.•N/S-doped TiO2 catalysts was proved efficient for the removal of 5 fluorouracil.•Defluorination followed by hydroxylation and oxidation are the main transformation pathways.•HO radicals are the main reactive radicals under simulated solar light.•1O2 and O2− oxidant species contributed significantly under visible light.
Although, several recent greenhouse studies are beginning to address the uptake of pharmaceuticals and personal care products (PPCPs) by a variety of crops, few studies have assessed the effects of ...exposure to complex, realistic wastewater effluents on uptake. Hence, in this study, a greenhouse experiment was conducted in order to study the interactions occurring exclusively between PPCPs in soil, and in the edible plant part of beets (Beta vulgaris) after exposure to treated wastewater effluent. According to the findings, the interactions between the pharmaceuticals caffeine (CFN) with bisoprolol (BSP), carbamezapine (CMZ), clarithromycin (CMC), metoprolol (MPL), sulfamethoxazole (SMX), and trimethoprim (TMP) occurring in soil were almost 99% synergistic; it was noted variability in the interactive capacity of the pharmaceuticals; the concentrations of pharmaceuticals which measured did not affect unfavorably beet yield; interactions between the PPCPs via the PPCPs contribution in plant and soil affect the qualitative and quantitative characteristics of the beets.
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•Interactions between pharmaceuticals occurring in soil were almost 99% synergistic.•Variability in the interactive capacity of the pharmaceuticals was noted.•Most of pharmaceuticals in soil did not affect unfavorably beet yield.•Interactions of pharmaceuticals and plant/soil, affect characteristics of beets.
Nanoparticles of TiO2 were synthesized and characterized by XRD, BET, TG/DTA and TEM measurements. The commercial azo dye Reactive Red 195 (RR195) was selected as a model dye in order to examine the ...adsorption capacity of TiO2 at room temperature, under dark conditions. It was demonstrated that RR195 could be efficiently adsorbed in aqueous suspension of TiO2. A study on the effects of various parameters like initial pH, concentration of dye and concentration of adsorbent has been carried out in order to find optimum adsorption conditions. The optimum pH of sorption was 3. Substantial reduction of COD, besides removal of colour, was also achieved. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. Equilibrium data fitted very well with the Langmuir model signifying the energetic homogeneity of TiO2 surface adsorption sites. At the temperature of 30 degrees C, the maximum monolayer adsorption capacity obtained from the Langmuir model is approximately 87 mg/g (pH 3.0). Kinetic studies were carried out and showed a rapid sorption of dye in the first 30 min while equilibrium was reached at 1h. Three kinetic adsorption models were used to describe the kinetics data, the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model. The sorption kinetics of dye was best described by the pseudo-second-order kinetic model.
A greenhouse experiment was conducted, using a randomized block design, including twelve heavy metal (Mn, Zn, Cu, Cd, Co, Cr, Ni, Pb) mixture treatments, with each metal participating in the ...treatment with 0, 2, 4, 6, 8, 10, and 12 mg/kg, respectively. Common beet (Beta vulgaris L.) was chosen as test plant. The plants were irrigated with treated municipal wastewater taken from the Wastewater Treatment Plant of the town of Amaliada, N.W., Peloponnese, Greece. The experiment aimed at studying the interactions between heavy metals and macro-microelements, and pharmaceuticals and personal care products (PPCPs). The basic scope was to shed some light on the potential environmental implications, of these interactions on the soil PPCPs for a more effective monitoring of these emerging contaminants in the plants and soil continuum. It was found that the PPCPs have a very high potential interactive capacity, having interacted with all the studied metals, and metalloids, as well as with plant macro elements (P, and K). The uptake of PPCPs by plants was statistically significantly related with their respective content in the soil. The general inference is that the interactive relations between heavy metals, macro-, microelements, and emerging contaminants, being mainly antagonistic, which contribute to the decrease the uptake of soil PPCPs.
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•The PPCPs interacted with the metals and metalloids.•The most studied soil metals and elements interact antagonistic on PPCPs.•The pH and soil pollution interacted with PPCPs mainly synergistically.
Highly active IrO2-modified Ti anodes have been prepared via a simple galvanic deposition process whereby a Ti substrate (freshly etched in boiling HCl containing fluoride ions) has been treated with ...an Ir(IV) solution, resulting in the reduction-deposition of Ir(IV) as metallic Ir on the surface of the Ti substrate with the simultaneous oxidation of nearby freshly etched Ti sites. Cyclic voltammetry of the resulting (Ir-TiO2)/Ti electrode in acidic solutions revealed features of IrO2 formation at positive applied potential values during continuous potential cycling. SEM micrographs showed good Ir dispersion on the Ti substrate, while EDS and XPS analysis of the deposits provided direct evidence for Ir and IrO2 presence on the surface of the electrodes. These electrodes, when tested as oxygen evolution reaction (OER) anodes by slow potential sweep voltammetry and constant potential amperometry, exhibited one of the highest mass specific activities for OER (560 mA mgIr−1) reported for IrO2 anode materials.
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•Galvanic deposition of Ir particles on a Ti substrate by a simple immersion method.•Electrochemical preparation of an IrO2/Ti anode.•Enhanced oxygen evolution reaction (OER) electrocatalytic activity.
•Degradation of CBZ during US, TiO2/UV and TiO2/UV/US processes has been evaluated.•The combined TiO2/UV/US oxidation resulted in significant enhancement of the CBZ degradation rate.•Transformation ...products were identified and the transformation pathways were proposed.•An acute toxicity test showed an increase in toxicity over the time-course of the studied processes.
This study examines the degradation of the antiepileptic carbamazepine (CBZ) by sonolysis, TiO2-based heterogeneous photocatalysis under UV-A and simulated solar irradiation, and by the combined use of UV-A and ultrasound irradiation (i.e. sonophotocatalysis) in demineralized water, ground water and effluent wastewater. The processes were compared with respect to substrate conversion rate and the extent of DOC reduction as a measure of mineralization. CBZ was degraded following a pseudo-first order kinetics. Sonophotocatalysis provided the highest rate of CBZ transformation over the time-course of the experiment while the degree of DOC removal in pure water was similar for all the studied treatments (around 40%), and always lower than CBZ conversion. This indicated that a considerable organic load remained in the treated solutions that could also be attributed to the presence of persistent oxidation products. UPLC–(+ESI)-QToF-MS was employed to determine major CBZ-related transformation products. Several recalcitrant hydroxy- and keto-derivatives of CBZ were tentatively identified. A Daphnia magna bioassay was used to evaluate the potential toxicity of the samples collected at different time points showing that the mixtures were highly toxic to D. magna.
In the present study, the coupling of adsorption capacity and photocatalytic efficiency of two different industrially produced titania catalysts was investigated and compared. The azo dye Reactive ...Red 195 was selected as a model compound. The tested catalysts, PK-10 and PK-180, exhibited different adsorption capacities due to their significant difference in their specific surface, but both have proven to be effective photocatalysts for photodegradation of the studied dye. PK-10 exhibited strong adsorption of the studied dye due to its high specific surface area, while the second studied catalyst, PK-180, demonstrated negligible adsorption of Reactive Red 195. The effect of the pH, the concentration of the catalyst and the initial concentration of the dye appear to affect the photocatalytic rate. The effect of the presence of humic acids and inorganic ions was also examined, while the contribution of various reactive species was indirectly evaluated through the addition of various scavengers. To evaluate the extent of mineralisation of the studied dye, total organic carbon (TOC) measurements during the experiment were also conducted. Besides total colour removal, evident reduction of TOC was also achieved using both catalysts.
