This paper reports a method for simultaneous determination of H2, O2, N2, CO, CO2, CH4, C2H2, C2H4, C2H6, C3H4 (propadiene and propyne), C3H6, C3H8 and C4H10 (n-butane and isobutane) by gas chromatography using thermal conductivity and flame ionization detectors. A single porous layer open tubular column (0.53 mm internal diameter ? 30 m length ? 30 µm thick) was applied and no catalytic converter was needed to convert CO and CO2 into CH4 to enable identification by a flame ionization detector. The most appropriate chromatographic conditions were defined for the method and it was validated according to the recommendations of the National Health Surveillance Agency and the National Institute of Metrology, Standardization and Industrial Quality. Chromatographic conditions defined for the target gases presented satisfactory linearity (r > 0.99), and limits of detection ranged between 0.0916 and 2.75 ppm. High accuracy (98-101%) obtained for the gas chromatography/thermal conductivity detector/flame ionization detector method associated to low relative standard deviation (?λτ; 2%) confirmed its applicability in routine quantification of target gases formed during the pyrolysis of municipal refuse-derived fuel.

The degradation of a pharmaceutical mixture (gemfibrozil, hydrochlorothiazide and naproxen) by TiO2/UV-A in different aqueous matrices was evaluated. The matrix components affected the operational conditions, rate constants, and removal efficiency of the pharmaceuticals, as well as toxicity. For sewage treatment plant effluent, a TiO2 concentration three-fold higher (450 mg L−1) and an irradiation time 1.5-3 times longer were required to reach the same efficiency of degradation as the pharmaceuticals in deionized water and surface water matrices. An improvement in the rate constants and the removal efficiency of the pharmaceuticals was achieved by adding 6 mg L−1 of H2O2 and 150 mg L−1 of TiO2 in deionized water and surface water, but not in the sewage treatment plant effluent, due to the coupling of 450 mg L−1 of TiO2 and 50-200 mg L−1 of H2O2. Overall, TiO2/UV-A efficiently degraded all compounds, but an additional step is needed for the removal of residual toxicity.

This study reports a protocol for the treatment of a sanitary landfill leachate through integration between a stage of coagulation-flocculation, a step of filtration of the resulting suspension, and application of the photo-Fenton process using a ferrioxalate complex and solar irradiation. The best results for turbidity removal by coagulation-flocculation were reached using Al3+ as nitrate salt mainly using concentrations up close 4.4 mmol L-1, at the natural pH of the effluent (pH 7.9), when the removal of 66% of the turbidity was achieved. By using a ferrioxalate complex after adjusting the pH of the effluent to 5, it was possible to circumvent the classical limitations of the Fenton process (related to the pH of the medium limited to between 2.5 and 3.0), performing a removal of 68% of the remaining dissolved organic carbon. The global dissolved organic carbon removal in this process was of 86% after a membrane filtration step before the photo-Fenton process.

In this study the coagulation-flocculation process was evaluated as an alternative for treatment of biodiesel wastewater. The role of two coagulants, Al3+ and Fe3+, as well as its dosage, pH, treatment time, stirring and aeration were evaluated. It was observed that in the treatment using Al3+ the pH of the effluent (9.7) does not need to be adjusted, while for Fe3+ a previous adjustment to pH 5.0 was necessary. On the other hand, a high concentration of Al3+ (243 mg L-1) and a relatively long treatment time (70 min) were required to reach more than 96% of turbidity removal, when compared to the processing using Fe3+ (56 mg L-1 and 53 min), attributed to the formation of different mole fractions of hydrolyzed cationic species. Under the optimized conditions, more than 96% of turbidity, apparent color and suspended solids, and 82% of oil and fats were removed.

In this study it was evaluated the role of the composition of sanitary landfill leachate on the removal of dissolved organic carbon (DOC) by photo-Fenton process. The composition of the matrix (high turbidity and color, as well as presence of inorganic ions sulfate and chloride) does not reduce the efficiency of DOC removal by photo-Fenton reactions, but influences significantly the reaction time and consumption of H2O2. An expressive increase in the efficiency of DOC removal occurred for concentrations of Fe2+ between 50 and 100 mg L-1, remaining constant in the range between 100 and 200 mg L-1. On the other hand, the pre-treatment of this effluent by coagulation-flocculation before the photo-Fenton process is recommended, since a similar efficiency of DOC removal, between 70 and 77%, was achieved using only 17% of the time and 7% of H2O2 necessary for the treatment of raw leachate treatment.

The photocatalytic performance of a composite based on the association of TiO2 and 2.5 wt.% of zinc(II) phthalocyanine (TiO2/ZnPc) was evaluated towards the mineralization of paracetamol and compared to that observed for the bare oxide in different pH and H2O2 concentrations. The results show that the photocatalytic performances were influenced by the pH, with maximum efficiency around the isoelectric point. Mineralization efficiencies between 86-91% was obtained using TiO2/ZnPc in pH 5.5-6.8, with 33 mg L-1 of H2O2, ca. 15% higher than that observed with TiO2. The mineralization efficiencies using bare TiO2 and TiO2/ZnPc were respectively 112 and 18% lower in the absence of H2O2. The better performance of TiO2/ZnPc is related to its extended light absorption and non-uniform coating of the TiO2 surface by ZnPc aggregates. Above pH 6.8, the mineralization efficiencies decrease for both photocatalysts, although the consumption of H2O2 remains above 90%, due to its decomposition in alkaline pH.

In this study, we evaluated the combination between an electrochemical process, occurring in the dark, and a heterogeneous photocatalytic process for dye degradation, using the azo dye tartrazine as model of oxidizable substrate. TiO2 P25 and an Ag-doped TiO2 were used as photocatalysts in suspensions containing 50 mg L–1 of tartrazine. The best result, 74% of dye mineralization in 120 min of reaction, was obtained using TiO2 P25 as photocatalyst and a current density of 10 mA cm–2 in the electrochemical cell, a value 30% higher than the sum of the results obtained by heterogeneous photocatalysis (44%) and electrochemical oxidation (13%). The use of Ag-doped TiO2 did not result in significant improvement on tartrazine mineralization, due to the aggregation of these nanoparticles. Our results suggest that this process can be an alternative for a complete treatment (discoloration and mineralization) of tartrazine and most likely other azo dyes.

A fotodegradação de cloranfenicol (CAP) em água ultrapura (UW), água superficial não tratada (USW), e efluente tratado de estação de tratamento de esgoto (TESTP) em escala de laboratório e planta piloto, foi avaliada usando radiação artificial e solar. Os resultados mostram, em todos os casos, que a degradação de CAP ocorre segundo uma cinética de pseudo-primeira ordem, com as constantes de velocidade de degradação aparente (k app) seguindo a ordem UW ≡ USW > TESTP. A k app e o tempo de meia-vida foram influenciados pela fonte de radiação. Produtos de transformação mono e di-hidroxilados foram identificados em UW após 40 min de irradiação solar, enquanto toxicidade aguda para Artemia salina aumentou de 35% para 100%, respectivamente após 180 e 1440 min, sob irradiação artificial e solar (94 e 132 kJ L-1), quando houve 99,2% e 97,7% de degradação de CAP. Os produtos de transformação não apresentaram atividade antimicrobiana.

The photodegradation of cloramphenicol (CAP) in ultrapure water (UW), untreated surface water (USW), and treated effluent from sewage treatment plant (TESTP) in laboratory scale and pilot scale, was evaluated using solar and artificial radiation. The results show, in all cases, that the CAP degradation occurs according to pseudo-first order kinetics, with the apparent degradation rate constants (k app) following the order UW ≡ USW > TESTP. The k app and half-life were strongly influenced by the radiation source. Mono- and di-hydroxyl transformation products were identified in UW after 40 min of solar irradiation, while the acute toxicity to Artemia salina increased from 35% to 100%, respectively after 180 and 1440 min of artificial and solar irradiation (94 and 132 kJ L-1), when 99.2 and 97.7% of CAP degradation occurred. The transformation products did not present antimicrobial activity.

Parâmetros que influenciam a eficiência da degradação do glifosato (adição única de Fe2+, adição simultânea de Fe2+ e Fe3+ numa razão molar de 1:1 (Fe2+/Fe3+), adição de íons oxalato e de H2O2) foram avaliados em escala de laboratório. Efeitos sinérgicos sobre a degradação e formação de fosfato foram observados utilizando a adição simultânea de Fe2+/Fe3+, bem como adicionando oxalato. Por outro lado, aumentos nas concentrações de Fe2+/Fe3+, oxalato e H2O2 não proporcionaram incremento linear da mineralização de glifosato e liberação de fosfato. Utilizando concentrações elevadas dessas espécies, a eficiência de mineralização de glifosato e de liberação de fosfato foi constante ou até mesmo reduzida. Sob condições otimizadas (0,27 mmol L-1 de Fe2+/Fe3+; 1,13 mmol L-1 de oxalato e 10,3 mmol L-1 de H2O2), os resultados obtidos em escala laboratorial e de planta piloto solar foram próximos. Uma relação direta entre a redução da toxicidade e concentração de glifosato também foi observada.

Parameters that influence the efficiency of the degradation of glyphosate (addition of Fe2+, simultaneous addition of Fe2+ and Fe3+ at a 1:1 (Fe2+/Fe3+) molar ratio, addition of oxalate and of H2O2) were evaluated at lab-scale. Synergic effects on its degradation and release of phosphate were observed using Fe2+/Fe3+, as well as adding oxalate. On the other hand, the concentration increase of Fe2+/Fe3+, oxalate and H2O2 did not promote a linear increase of glyphosate mineralization and release of phosphate. Using high concentrations of these species, the efficiency of glyphosate mineralization and release of phosphate was constant or even decreased. Under optimized conditions (0.27 mmol L-1 of Fe2+/Fe3+; 1.13 mmol L-1 of oxalate and 10.3 mmol L-1 of H2O2), close results for mineralization and release of phosphate were obtained in lab-scale and using a solar pilot plant. A direct ratio between reducing the toxicity and glyphosate concentration was also observed.

Este trabalho descreve a influência e otimização dos reagentes de Fenton (concentração de Fe2+ e H2O2) na eficiência da mineralização do herbicida paraquat (PQT, 50 mg L-1) em água, após 60 min (equivalendo a 642 kJ L-1 de radiação UVA acumulada) de tratamento por processo foto-Fenton em escala de laboratório, usando planejamento composto central (CCD). Sob condições otimizadas, experimentos cinéticos foram feitos, avaliando a remoção do PQT, sua mineralização e toxicidade em escala de laboratório, usando irradiação artificial, e em planta piloto sob irradiação solar. A mesma eficiência de remoção e mineralização do PQT foram obtidas em ambos os reatores utilizados. A toxicidade das amostras, estimada em termos de mortalidade de Artemia salina, diminui simultaneamente com o decaimento da concentração de PQT, sugerindo a formação de intermediários de menor toxicidade. Dessa maneira, o processo foto-Fenton/solar pode ser considerado uma alternativa viável para o tratamento de águas residuais contendo PQT.

This study describes the influence and optimization of Fenton's reagent (concentration of Fe2+ and H2O2 ) on the efficiency of mineralization of the herbicide paraquat (PQT, 50 mg L-1) in water, after 60 min (equivalent to 642 kJ L-1 of accumulated UVA radiation) treatment by photo-Fenton process in laboratory scale, using central composite design (CCD). Under optimized conditions, kinetic experiments were done, evaluating the PQT removal, its mineralization and toxicity in laboratory scale, using artificial irradiation, and in a pilot plant under solar irradiation. The same removal efficiency and mineralization of PQT were obtained in both reactors. The toxicity of the samples, estimated in terms of mortality of Artemia salina, decreases simultaneously with the decay of concentration of PQT, suggesting the formation of intermediates of lower toxicity. In this way, the solar photo-Fenton process can be considered as a viable alternative for the treatment of wastewater containing PQT.

A influência do pH na degradação do fármaco diclofenaco (DCF) por processo foto-Fenton/solar foi avaliada usando o complexo citrato de amônio e ferro(III) (FecitNH4). Embora a eficiência de degradação diminua com o aumento do pH (no intervalo de pH de 5 a 8), a concentração de DCF ficou abaixo do limite de detecção após 45 min de irradiação enquanto que 77% do carbono orgânico total foi removido após 150 min em pH 7 (sem ajuste posterior). Foi verificada cinética de primeira ordem para a degradação de DCF, cuja constante de velocidade aumentou com o aumento das concentrações de FecitNH4 e H2O2. Menor degradação de DCF foi observada quando presente na matriz efluente de estação de tratamento de esgoto (ETE), devido principalmente à alta concentração de carbonato e bicarbonato em pH 7. Entretanto, após ajuste de pH para 5, a concentração de DCF ficou abaixo do limite de detecção após 75 min de irradiação.

The influence of pH on the degradation of the pharmaceutical diclofenac (DCF) by the solar/photo-Fenton process was investigated using ammonium iron(III) citrate complex (FecitNH4). Although the degradation efficiency decreased as the pH increased (in the pH range 5 to 8), the DCF concentration was lower than its limit of detection after 45 min irradiation while 77% of the total organic carbon was removed after 150 min irradiation at initial pH 7 (without further adjustment). A pseudo-first-order kinetics of DCF degradation was observed, which kinetic constant increased with the increase of the concentrations of FecitNH4 and H2O2. Lower DCF degradation was observed when present in a sewage treatment plant (STP) effluent sample, mainly due to the high concentration of carbonate and bicarbonate at pH 7. However, after adjusting the pH to 5, the DCF concentration was lower than its detection limit after 75 min irradiation.

Este trabalho descreve a utilização do processo Fenton para degradação de diesel em solo e destaca aspectos comuns em situações reais de contaminação que podem afetar a eficiência da remediação. Foi observado que a maior parte dos hidrocarbonetos presentes no diesel com menos de 14 carbonos foi perdida por volatilização antes da remediação. Em solo franco, cerca de 80% do diesel foi degradado enquanto que em solo franco-argiloso a degradação foi inferior a 20%. Adições múltiplas de H2O2 proporcionaram degradação de até 80% do diesel, enquanto que com adição única a degradação foi inferior a 14%. A adição de ferro solúvel foi essencial para obtenção de altas porcentagens de degradação. Não foi observado aumento significativo (t-test; P = 0.05) na degradação do diesel quando foram utilizadas dosagens de H2O2 entre 0,09 e 0,36 g g-1. Além disso, a alta dosagem de H2O2 (0,36 g g-1) degradou 87% da matéria orgânica originalmente presente no solo.

This work reports the use of Fenton process for diesel degradation and addresses common aspects of real situations that can affect the soil remediation efficiency. It was observed that most of diesel hydrocarbons containing less than 14 carbon atoms were lost by volatilization prior to the treatment. About 80% degradation was achieved in a loam soil, while less than 20% was observed in a clay loam soil. The multiple additions of H2O2 resulted in 80% diesel degradation, while only 14% of diesel was degraded after a reaction time of 80 h using a single addition. The addition of soluble iron was essential to achieve high degradation levels. No significant increase in diesel degradation (t-test; P = 0.05) was observed using H2O2 dosages between 0.09 and 0.36 g g-1. Furthermore, the highest H2O2 dosage applied (0.36 g g-1) degraded around 87% of the organic matter originally present in the soil.

Wastewater and soil treatment processes based on Fenton's reagent have gained great attention in recent years due to its high oxidation power. This review describes the fundaments of the Fenton and photo-Fenton processes and discusses the main aspects related to the degradation of organic contaminants in water such as the complexation of iron, the use of solar light as the source of irradiation and the most important reactor types used. An overview of the main applications of the process to a variety of industrial wastewater and soil remediations is presented.