No abstract

No abstract

The photocatalytic degradation of textile effluent was investigated using TiO, ZnO, and NbO catalysts under solar irradiation. The procedures were carried out at ambient conditions in April 2014, with pH 3.0 and catalyst concentration of 0.250 g L. The photocatalytic activity of the oxides was evaluated by means of kinetic efficiency (rate constant and half-life time), chemical oxygen demand reduction, and absorbance reduction at 228, 254, 284, 310, 350, 500, and 660 nm (λ). Mineralization in terms of the formation of inorganic ions and toxicity reduction using bioassays with Artemia salina were performed. TiO reduced the absorbance at 660 nm (λ) after 300 min of solar irradiation around 94 and 93%; and 68 and 60% of COD, respectively. ZnO showed lower photocatalytic activity giving 64 and 42% of absorbance and COD reduction, respectively. The photocatalytic activity of NbO was very close to TiO-P25. In this sense, NbO becomes a promising alternative to replace the commercial TiO-P25. Bioassays confirmed the efficacy of treatment, increasing the lethal concentration of 27.59 (in natura) to 131.95% in the presence of NbO.

The present work investigated the degradation of a dyeing factory effluent by advanced oxidative process under UV irradiation. TiO and ZnO were used as catalysts and the influence of different concentrations of HO added to the system was studied. The catalysts were characterized in terms of crystal structure (X-ray diffraction), textural properties (Brunauer-Emmett-Teller area and pore volume) and point of zero charge, which indicated the semiconductors had a positively charged surface in an acidic medium. After 8 h of irradiation at pH 3.0 and catalyst concentration of 0.0625 g L, the effect of HO was evaluated by means of kinetic efficiency (rate constants), absorbance reduction (at 284, 621 e 669 nm), total organic carbon reduction and mineralization (in terms of the formation of ions such as [Formula: see text] and [Formula: see text]). Adding HO to the photocatalytic system significantly increased pollutants' removal, highlighting tests with 1.0 × 10 mol L, showing higher absorbance reduction and rate constants at 621 and 669 nm for TiO and best mineralization rates for ZnO. Ecotoxicity bioassays using Artemia salina L confirmed the treatment efficacy, with effluent lethal concentration (LC) increasing from 65.68% (in natura) to over 100% after photocatalysis treatment.

No abstract

Calcium titanate zirconate, Ca(TiZr)O (CZT), powders have been synthesised by the polymeric precursor method. The structural analysis of the CZT powders was monitored by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS) and textural analysis. The photocatalytic properties were evaluated by methylene blue (MB) decomposition and real textile wastewater (RTW) combined treatment (coagulation/flocculation/photocatalysis). Chemical oxygen demand (COD) of RTW was successfully reduced from 6195 mg L (untreated) to 662 mg L after coagulation/flocculation with a tannin-based coagulant (Tanfloc®) and finally to 471 mg L after combined treatment (coagulation/flocculation/photocatalysis) applying ultraviolet radiation and CaTiO as photocatalyst.

ABSTRACT. The large volume of sugar cane vinasse generated by alcohol distillation motivated current treatment to reduce vinasse volume by a concentration process and to eliminate pollutants in the wastewater. The vinasse concentration by the coagulation/flocculation process favored the use of the thickened sludge either for fertilizing purposes or for biogas production. The photocatalysis treatment of the clarified vinasse mineralized pollutants and reduced toxicity, with subsequent water reuse. The first series of coagulation/flocculation experiments were carried out in a jar-test apparatus at room temperature with samples of 200 mL and several coagulant concentrations. In the second series of experiments, photocatalysis tests were performed on the clarified vinasse obtained by coagulation/flocculation under conditions optimized in the first series of experiments. The photocatalysis tests were performed for five consecutive days with UV irradiation, using TiO 2 -P25 as photocatalyst. Significant reduction of toxicity, consistent with the reduction in chemical oxygen demand (COD), was found when the photocatalysis treatment subsequent to coagulation/flocculation process was employed. Further, 98% reduction of turbidity and 87% reduction of color were obtained by the coagulation/flocculation process. Coupled to the photocatalysis process, significant reductions in absorbance, toxicity and COD (80%) were also achieved.Keywords: vinasse, coagulation/flocculation, photocatalysis, TiO 2 , vegetable tannin.Tratamento de vinhaça utilizando coagulante tanino vegetal e fotocatálise RESUMO. O grande volume de vinhaça de cana-de-açúcar produzido por destilarias de álcool motivou o processo de tratamento proposto, visando à redução desse volume por um processo de concentração e eliminação de poluentes nas águas residuais. A concentração de vinhaça por meio de um processo de coagulação/floculação permitiu a utilização do lodo espessado como fertilizante ou na produção de biogás, enquanto o tratamento fotocatalítico da vinhaça clarificada promoveu a mineralização dos poluentes e reduziu a toxicidade, permitindo a reutilização da água. A primeira série de experimentos de coagulação/floculação foi realizada em aparelho de jar-test em temperatura ambiente, com amostras de 200 mL e com variação da concentração de coagulante. Na segunda série de experimentos, testes fotocatalíticos foram realizados com a vinhaça clarificada obtida por coagulação/floculação em condições otimizadas na primeira série de experimentos. Os testes fotocatalíticos foram realizados por cinco dias consecutivos com irradiação UV, usando TiO 2 -P25 como fotocatalisador. Foi encontrada significativa redução da toxicidade, consistente com a redução da demanda química de oxigênio (DQO), ao utilizar o tratamento fotocatalítico após a coagulação/floculação. Com o processo de coagulação/floculação foram obtidos 98% de redução da turbidez e 87% de redução da cor. Em combinação com o processo fotocatalítico, reduções significativas na absorbância, toxicidade e DQO (...

ABSTRACT. In this work, the effect of vinasse pre-treatment and anatase content in the photocatalytic degradation of sugarcane vinasse was evaluated. The in nature vinasse was pretreated by coagulation/flocculation using vegetal tannin as coagulant and diluted 1: 2 with deionized water. The photocatalytic tests with in nature, pretreated and diluted vinasse were performed for 48 hours under UV radiation using 1 g of catalyst: TiO 2 Kronos calcined at 300 o C (100% anatase) and 1000 o C (34% anatase) and TiO 2 P25 (87% anatase). The process of coagulation/flocculation removed about 50, 85 and 97% of COD, color and turbidity of in nature vinasse, respectively. The results showed that despite the slight COD decrease of in nature vinasse, its toxicity was significantly reduced after photocatalytic treatment, especially when TiO 2 -34 and TiO 2 -87 were used. This behavior shows that the mixture of anatase and rutile phases showed a positive synergistic effect. Regarding pre-treatment of vinasse, the coagulation/flocculation process was more efficient, promoting the greatest reductions of COD (67%) and toxicity (up to 10 times).Keywords: vinasse, coagulation/flocculation, photocatalysis, toxicity.Fotodegradação da vinhaça: avaliação do efeito do pré-tratamento da vinhaça e da fase cristalina do TiO 2 RESUMO. Neste trabalho, foi avaliado o efeito do pré-tratamento da vinhaça e do teor de anatase na degradação fotocatalítica da vinhaça. A vinhaça in natura foi pré-tratada por coagulação/floculação usando tanino vegetal como coagulante e diluição 1:2 com água deionizada. Os testes fotocatalíticos com a vinhaça in natura, pré-tratada e diluída foram realizados durante 48h sob radiação UV utilizando 1 g de catalisador: TiO 2 Kronos calcinado a 300 o C (100% anatase) e a 1000 o C (34% anatase) e TiO 2 P25 (87% anatase). O processo de coagulação/floculação removeu cerca de 50, 85 e 97% de DQO, cor e turbidez da vinhaça in natura, respectivamente. Os resultados mostraram que apesar da pequena redução de DQO da vinhaça in natura, sua toxicidade foi reduzida significativamente após tratamento fotocatalítico, principalmente quando TiO 2 -34 e TiO 2 -87 foram utilizados. Esse comportamento evidencia que a mistura das fases anatase e rutile apresentou efeito sinérgico positivo. Em relação ao pré-tratamento da vinhaça, o processo de coagulação/floculação se mostrou mais eficiente, promovendo as maiores reduções de DQO (67%) e toxicidade (até 10 vezes).Palavras-chave: vinhaça, coagulação/floculação, fotocatálise, toxicidade.