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.
The generation of leachate, from the disposal of waste in sanitary landfills, is a major socioeconomic and environmental issue that deserves special attention. The particularly complex composition ...and the hazardous nature of some pollutants that are present in landfill leachate make evident the necessity of developing effective treatment methods. UV/Fe2+/H2O2 process seems to be a particularly useful tool for removing the organic load, thus reducing the toxicity effect of landfill leachate. In this research paper, such a process was applied in a stabilized and a biologically pretreated leachate sample with the aim of examining the ecotoxicity and phytotoxicity abatement before and after the chemical oxidation. The findings showed that UV-Fenton process can give excellent results, achieving 85.14% COD and 88.35% TOC removals of the stabilized leachate in lab-scale applications and 66.36% COD reduction in pilot-scale application, under the same experimental conditions (H2O2:COD = 3:1, Fe2+ /H2O2 = 1:10, treatment time = 180 min and pH = 3). Additionally, the results from the phytotoxicity tests, using Sorghum saccharatum seeds, revealed that chemical oxidation was able to reduce the toxic effects of landfill leachate, although it couldn't degrade completely the hazardous compounds. Similar conclusions were drawn by ecotoxicity tests with Daphnia magna, whose mortality was markedly lower in the treated samples. The above findings can serve as an adequate basis for future research studies so as to develop efficient treatment approaches.
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•Laboratory and pilot scale treatment of landfill leachates.•UV/Fe2+/H2O2 process reduces the organic content of landfill leachates.•UV-Fenton caused abatements of phytotoxicity and ecotoxicity values.•Phytotoxicity results indicate the reuse of landfill leachates for irrigation.
In the present study, photo-Fenton and Fenton-like processes were investigated for the degradation and mineralization of the antineoplastic drug 5-fluorouracil (5-FU). For the optimization of ...photo-Fenton treatment under simulated solar light (SSL) radiation, the effects of several operating parameters (i.e., 5-FU concentration, Fe
3+
, and oxidant concentration) on the treatment efficiency were studied. According to the results, SSL/Fe(C
2
Ο
4
)
3
3−
/Η
2
Ο
2
process was the most efficient, since faster degradation of 5-FU and higher mineralization percentages were achieved. All the applied processes followed quite similar transformation routes which include defluorination-hydroxylation as well as pyrimidine ring opening, as demonstrated by the transformation products identified by high resolution mass spectrometry analysis. The toxicity of the treated solutions was evaluated using the Microtox assay. In general, low toxicity was recorded for the initial solution and the solution at the end of the photocatalytic treatment, while an increase in the overall toxicity was observed only at the first stages of SSL/Fe
3+
/Η
2
Ο
2
and SSL/Fe
3+
/S
2
O
8
2−
processes.
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.
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.
The photochemical degradation of the antidepressant drug venlafaxine (VNF) by UV/TiO
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/TiO
can lead to the elimination of parent compound and the detoxification of the solution.
Green macroalgae were collected from four locations in the Thermaikos Gulf, Greece, and heavy-metal concentrations were measured. Two of the sampling locations were not directly impacted by a ...specific pollution source, but the other two were. Samples were collected monthly over a 1 yr period, during which time heavy-metal concentrations in seawater were also determined. Results showed that heavy-metal bioaccumulation was higher in Enteromorpha sp. than in Ulva sp. In both species, iron was bioaccumulated most strongly, followed by manganese, zinc, lead, chromium, copper, and cadmium. The sampling site proved to be a very significant source of variation in metal concentrations, while sampling period was significant only for Cr, Cd, and Zn in Ulva sp.
The purpose of the present study was the assessment of the potential reusability of landfill leachates for agricultural irrigation, after advanced oxidation treatments. The UV/Fenton and Fenton ...processes were applied to the treatment of two different landfill leachate samples, L1 and L2, classified as intermediates, collected from two different landfills located in Macedonia, Greece. Samples were characterized by high COD and TOC values, ranging from 5500-6100 mg/l and 1700-1780 mg/l, respectively. The treatment efficacy and toxicity characteristics were evaluated by conducting phytotoxicity tests. Sorghum saccharatum seeds were used and the germination index (GI) was estimated. The results showed that the UV/Fenton process achieved better organic matter removal rates for both samples. The untreated undiluted leachates L1 and L2 were highly toxic, resulting in GI values of 0. The results of the study showed that Sorghum saccharatum seed germination depends on the nature of the irrigation media and that optimum germination rates were achieved at dilutions of treated leachates with ratios higher than 1:4.
