RESUMEN
An experimental study of the homogeneous Fenton and photo-Fenton degradation of 4-amidophenol (paracetamol, PCT) is presented. For all the operation conditions evaluated, PCT degradation is efficiently attained by both Fenton and photo-Fenton processes. Also, photonic efficiencies of PCT degradation and mineralization are determined under different experimental conditions, characterizing the influence of hydrogen peroxide (H2O2) and Fe(II) on both contaminant degradation and sample mineralization. The maximum photonic degradation efficiencies for 5 and 10 mg L(-1) Fe(II) were 3.9 (H2O2 = 189 mg L(-1)) and 5 (H2O2 = 378 mg L(-1)), respectively. For higher concentrations of oxidant, H2O2 acts as a "scavenger" radical, competing in pollutant degradation and reducing the reaction rate. Moreover, in order to quantify the consumption of the oxidizing agent, the specific consumption of the hydrogen peroxide was also evaluated. For all operating conditions of both hydrogen peroxide and Fe(II) concentration, the consumption values obtained for Fenton process were always higher than the corresponding values observed for photo-Fenton. This implies a less efficient use of the oxidizing agent for dark conditions.
Asunto(s)
Acetaminofén/química , Acetaminofén/efectos de la radiación , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/efectos de la radiación , Acetaminofén/análisis , Compuestos Ferrosos/química , Peróxido de Hidrógeno/química , Oxidación-Reducción , Procesos Fotoquímicos , Contaminantes Químicos del Agua/análisisRESUMEN
This work studied the photocatalysed oxidation of the antibiotic oxolinic acid (OA) in an annular reactor operated with immobilized TiO(2) on sintered glass cylinders (SGC). Experiments were carried out in 1l solution of OA (18 mg l(-1)) at pH 9 with oxygen bubbling. Irradiation was performed with black light (36 W). The reaction was monitored by COD, TOC and average oxidation state (AOS) calculations. The antibacterial activity of intermediates was followed using the inhibition halo technique on Escherichia coli cultures. The initial antibiotic concentration decreases in one order of magnitude after 60 min irradiation, and was completely eliminated at 100 min reaction. The TOC was reduced in 54% and the AOS reach values around +3 indicating the formation of low molecular weight carboxylic acids. The oxidation reaction fit well with the Langmuir-Hinshelwood kinetic model indicating the dependence of reaction rate with initial adsorption step. The antibacterial activity of the solution decreases with antibiotic removal, demonstrating that intermediates do not present antibiotic activity.
Asunto(s)
Ácido Oxolínico/química , Titanio/química , Catálisis , Oxidación-Reducción , Fotoquímica , Espectrofotometría UltravioletaRESUMEN
Titanium dioxide was obtained in its pure form (TiO2) and in the presence of urea (u-TiO2) and thiourea (t-TiO2) using the sol-gel technique. The obtained powders were characterized by BET surface area analysis, Infrared Spectroscopy, Diffuse Reflectance Spectroscopy and the Rietveld refinement of XRD measurements. All the prepared catalysts show high anatase content (>99%). The a and b-cell parameters of anatase increase in the order TiO2
Asunto(s)
Antibacterianos , Fluoroquinolonas , Luz Solar , Titanio/química , Contaminantes Químicos del Agua , Purificación del Agua/métodos , Antibacterianos/química , Antibacterianos/efectos de la radiación , Catálisis , Fluoroquinolonas/química , Fluoroquinolonas/efectos de la radiación , Fotoquímica , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
Degradation of 2.5 mM EDTA-Fe solution was performed in a coupled photocatalytic-biological reactor. The system consists of a photochemical annular reactor filled with TiO2 immobilized on glass Raschig rings coupled with an activated sludge continuous reactor. Around 50% of EDTA degradation was reached after 150 min irradiation. Simultaneously a four-fold increase in biodegradability, measured as BOD5/COD ratio, was observed. The activated sludge is not capable to degrade the complex EDTA-Fe but it removed partially the COD and efficiently the BOD5 of the photochemically treated solution.
Asunto(s)
Compuestos Férricos/aislamiento & purificación , Quelantes del Hierro/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Biodegradación Ambiental , Reactores Biológicos , Catálisis , Ácido Edético/química , Ácido Edético/aislamiento & purificación , Ácido Edético/metabolismo , Ácido Edético/efectos de la radiación , Compuestos Férricos/química , Compuestos Férricos/metabolismo , Compuestos Férricos/efectos de la radiación , Quelantes del Hierro/química , Quelantes del Hierro/metabolismo , Quelantes del Hierro/efectos de la radiación , Oxidación-Reducción , Aguas del Alcantarillado , Titanio/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismo , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
The interactions of TiO2 with phospholipid bilayers found in cell membrane walls were observed to perturb the bilayer structure under UVA light irradiation. The structure changes in the phospholipid bilayers upon contact with TiO2 under light and in the dark were followed by X-ray diffraction. Hydration effects at the semiconductor-phospholipid interface played an important role in the degradation of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) bilayers taken as cell wall lipid bilayer models. Evidence is provided that the fluidity of the phospholipid bilayers plays a significant role when interacting in the dark with the TiO2 or in processes mediated by TiO2 under light irradiation.
Asunto(s)
Membrana Dobles de Lípidos , Fosfolípidos/química , Semiconductores , Titanio/química , Agua/química , Catálisis , Fotoquímica , Difracción de Rayos XRESUMEN
Leather tanning effluents are a source of severe environmental impacts. In particular, the unhairing stage, belonging to the beamhouse processes, generates an alkaline wastewater with high concentrations of organic matter, sulphides, suspended solids, and salts, which shows significant toxicity. The objective of this work was to evaluate the biodegradation of this industrial wastewater by combined oxidative and biological treatments. An advanced oxidation process (AOP) with Fenton's reagent was used as batch pretreatment. The relationships of H2O2/Fe2+ and H2O2/COD were 9 and 4, respectively, reaching an organic matter removal of about 90%. Subsequently, the oxidised beamhouse effluent was fed to an activated sludge system, at increasing organic load rates (OLR), in the range of 0.4 to 1.6 g COD/L x day. The biological organic matter removal of the pre-treated wastewater ranged between 35% and 60% for COD, and from 60% to 70% for BOD. Therefore, sequential AOP pretreatment and biological aerobic treatment increased the overall COD removal up to 96%, compared to 60% without pretreatment. Bioassays with D. magna and D. pulex showed that this kind of treatment achieves only a partial toxicity removal of the tannery effluent.
Asunto(s)
Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Animales , Biodegradación Ambiental , Bioensayo , Bovinos , Daphnia , Peróxido de Hidrógeno/química , Hierro/química , Oxidantes/química , Oxidación-Reducción , Oxígeno/análisis , Oxígeno/metabolismo , Piel , Contaminantes Químicos del Agua/toxicidadRESUMEN
Mineralization of a 5 mM EDTA solution at pH 3 was evaluated via TOC removal under UV-C irradiation in the presence of H2O2 at various conditions. The highest TOC removal (78%) was obtained using a 40:1 H2O2/EDTA molar ratio, after 540 min irradiation. However, a 20:1 ratio gave slightly lower results, being economically more attractive. Best results of TOC removal were obtained under pH controlled conditions. Addition of TiO2 (1 g l(-1)) was detrimental, even in the presence of H2O2, indicating that at this concentration, TiO2 inhibits the mineralization, probably by scattering or by screening of the light.
Asunto(s)
Quelantes/aislamiento & purificación , Ácido Edético/aislamiento & purificación , Peróxido de Hidrógeno/química , Oxidantes/química , Purificación del Agua/métodos , Quelantes/química , Ácido Edético/química , Concentración de Iones de Hidrógeno , Residuos Industriales , Rayos UltravioletaRESUMEN
Photocatalysis using ZnO-Fe2O3 coupled catalyst removed partially the organic matter dissolved in kraft black liquor obtained from pinus wood cooking. The photo-assisted oxidation using different ZnO/Fe2O3 ratios was studied following the CO, evolution during the course of the reaction. A synergy of the composite improves the mineralization observed. The optimal ZnO to Fe2O3 ratio varied from 0.5 to 0.7 which allowed the highest mineralization rates.
Asunto(s)
Compuestos Férricos/química , Lignina/química , Semiconductores , Administración de Residuos/instrumentación , Óxido de Zinc/química , Catálisis , Humanos , Papel , Administración de Residuos/métodosRESUMEN
The photocatalytic degradation of three reactive azo dyes (yellow-2, orange-16 and red-2) and one anthraquinone reactive dye (blue-19) was studied. The reactions were carried out in a reactor with recirculation using TiO2 immobilised on glass Raschig rings (system A) and compared with a batch system using the catalyst in aqueous suspension (system B). Both reaction systems were irradiated with a 125 W, lambda > 254 nm lamp. The suspended TiO2 system was also studied using a 125 W 360 nm lamp (system C). Kinetic studies indicated a rapid colour removal, following the order B > A > C. The same trend was observed in COD and TOC removal profiles. The energy consumption per order of magnitude of catalytic degradation of the dyes was lower in the batch reactor (system B) than in the reactor with recirculation and immobilised TiO2 (system A).
Asunto(s)
Compuestos Azo/química , Colorantes/química , Titanio/química , Catálisis , Oxígeno , Fotoquímica , Industria Textil , Purificación del Agua/métodosRESUMEN
A cellulose bleaching effluent (E1) was degraded in batch conditions by photocatalysis using TiO2 and ZnO supported on glass Raschig rings. The effluent was completely decolourised and the total phenol content was reduced by 85% after 120 min treatment with both catalysts. Partial mineralization of the organic matter was confirmed by total organic carbon (TOC) reduction, approximately 50%. The residual organic matter shows a low acute toxicity as compared to the initial values and AOX values are strongly reduced after the photocatalytic oxidation. Molecular mass distribution showed that high molecular mass compounds were almost completely degraded.
Asunto(s)
Celulosa/metabolismo , Colorantes/metabolismo , Titanio/metabolismo , Eliminación de Residuos Líquidos/métodos , Óxido de Zinc/metabolismo , Catálisis , Color , Papel , FotoquímicaRESUMEN
The oxidation of a 186 ppm 6-chlorovanillin solution was performed using impregnated TiO2 glass rings in a 1 l photochemical reactor. Fifty per cent degradation was obtained after 60 min with recirculation of the solution. Then, oxidised samples were submitted under aerobic conditions to bacterial degradation in the Pseudomonas paucimobilis (S37) and Burkholderia cepacia (PZK). Both selected aerobic bacteria degrade more efficiently the photocatalysed samples, being PZK strain better than S37. A first-order kinetic was observed in both systems photocatalytic and bacterial degradation.
Asunto(s)
Pseudomonas/metabolismo , Microbiología del Suelo , Ácido Vanílico/metabolismo , Biodegradación Ambiental , Catálisis , Colorantes/química , Industrias , Oxidación-Reducción , Papel , Fotoquímica , Titanio/química , Ácido Vanílico/análogos & derivados , Eliminación de Residuos LíquidosRESUMEN
The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied. The initial biodegradability of the organic matter present in the effluent, estimated as the BOD5/COD, was low (0.3). When the effluent was submitted to ozonation and to five different advanced oxidation systems (O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, O2/UV/TiO2), the biodegradability increase significantly. After five minutes of reaction, the O3/UV system appears as the most efficient in to transform the organic matter to more biodegradable forms. A similar effect was observed when the effluent was submitted to an activated sludge treatment. The COD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments.