Physiological changes in green and red cherry tomatoes after photocatalytic ethylene degradation using continuous air flux.

In this work photocatalytic ethylene degradation (TiO2-UV) was applied in green cherry tomatoes with the aim to control biochemical and physiological changes during ripening. Photocatalytic process was performed at 18 °C ± 2 °C and 85% HR for 10 days using continuous air flux. Ethylene, O2 and CO2 concentration from cherry tomatoes under TiO2-UV and control (c) fruits, were measured by GC-MS for 10 days. After that, the tomatoes were stored for 20 days. During the photocatalysis process, ethylene was completely degraded and control fruits, the ethylene was 28.73 nL/g. Respiration rate was lower for fruits under TiO2-UV than control. During storage period, cherry tomatoes treated by TiO2-UV, showed lower ethylene concentration, respiration rate, total soluble solid, lycopene, sugar and organic acid content than control showing that the fruits treated with photocatalysis did not reach the full maturity. In addition, all the cherry tomatoes showed different maturity stages. Fungal incidence was higher in control fruits than fruits treated with photocatalysis. This research showed for the first time that photocatalytic technology preserved the physiological quality of cherry tomatoes for 30 days of storage, being a promised technology to preserve cherries tomatoes.

An investigation of scale effect and applicability of compact light sources in microchannel reactors applied to pollutant abatement.

In this work, the performance of microreactors irradiated with conventional (fluorescent) and UV-LED light was evaluated. For this purpose, a microfluidic reactor with an equivalent diameter of 133.5 µm was used. In addition, the effect of scale variation on the performance of photochemical reactors was assessed using reactors with three internal diameters (600, 1200, and 2300 µm), 2 residence times (30 and 60 s), and two sources of UVA radiation (A with irradiance of 115 W m-2 and B with irradiance of 44 W m-2). Also, the relationship between the configuration of the photocatalyst film and the effect of the scale on the performance of photochemical reactors was experimentally and theoretically investigated. For both cases, methylene blue dye was used as a model pollutant and titanium dioxide (TiO2) as a photocatalyst deposited on the inner wall of the photocatalytic reactors. For the residence time of 30 s, the smaller the reactor diameter, the greater was the degradation (22, 18, and 6%, respectively, for lamp A and 17, 16, and 8 %, respectively, for lamp B). The influence of the diameter of the reactor was also observed for the residence time of 60 s, but only for the reactor with a 2300-µm internal diameter. The reactors with diameters 600 and 1200 µm only showed different results when illuminated with lamp B (33 and 28% of methylene blue conversion, respectively). Moreover, computational simulation results suggested higher efficiency as the reactor's diameter is decreased and an optimum thickness of photocatalyst film to maximize the performance of devices in which photocatalytic reactions are carried out.

Photocatalytic effect of addition of TiO2 to acrylic-based paint for passive toluene degradation.

Volatile organic compounds (VOCs) are known to be hazardous and associated with several human health problems. Thus, many technologies have been developed in recent years for their removal, such as thermal catalysis, photocatalysis and ozonization. In this study, the main objective was to evaluate the effects of incorporating titanium dioxide into an acrylic-based paint for gaseous toluene abatement. Paints with photocatalytic properties were prepared by adding TiO2 P25 powder to an acrylic-based paint, using the following proportions: 0, 10, 15, 20 and 50 wt% (dry basis). Toluene and CO2 concentrations at the reactor input and output were determined using GC/MS, and GC/FID, respectively, and the toluene conversion and CO2 formation were assessed. The compounds adsorbed onto photocatalytic paints were extracted and then identified by GC/MS. The results indicated that the addition of 50 wt% of TiO2 P25 results in a paint of reduced quality. The addition of 20 wt% of TiO2 P25 to the paint led to higher values for the photocatalytic conversion of toluene to CO2. The occurrence of two simultaneous processes was observed: the photocatalytic oxidation of toluene to CO2 and the self-degradation of the organic compounds, such as polymeric acrylic, in the paint. The adsorption of different compounds onto the photocatalytic paints was identified by GC/MS analysis. The use of photocatalytic paints is a promising technique for toluene abatement, but it requires further study and improvement particularly with regard to the effects of the self-degradation of the paint.

Treatment of aqueous solutions of 1,4-dioxane by ozonation and catalytic ozonation with copper oxide (CuO).

In this study, treatment for the removal of 1,4-dioxane by ozone and by catalytic ozonation using CuO as the catalyst was investigated. While the removal of 1,4-dioxane was small (20%) and mineralization negligible after 6 h of ozonation treatment, the removals of 1,4-dioxane and total organic carbon increased by factors of 10.35 and 81.25, respectively, after catalytic ozonation in the presence of CuO. The mineralization during catalytic ozonation was favoured at pH 10 (94.91 min-1), although it proceeded even at pH 3 (54.41 min-1). The CuO catalyst decreased the equilibrium concentration of soluble ozone and favoured its decomposition to reactive oxidative species. Radical scavenging experiments demonstrated that superoxide radicals were the main species responsible for the degradation of 1,4-dioxane. Further scavenging experiments with phosphate confirmed the presence of Lewis active sites on the surface of CuO, which were responsible for the adsorption and decomposition of ozone. The reaction mechanism proceeded through the formation of ethylene glycol diformate, which quickly hydrolyzed to ethylene glycol and formic acid as intermediate products. The stability of CuO indicated weak copper leaching and high catalytic activity for five recycling cycles. The toxicity of the water, assessed by Vibrio fischeri bioluminescence assays, remained the same (low toxicity) after catalytic ozonation while it increased after treatment with ozonation alone.

Liming as a means of reducing copper toxicity in black oats / Calagem como forma de redução da toxidez por cobre em aveia preta

ABSTRACT: Soils which are cultivated with grapevines have high available copper (Cu) content, which can be toxic to cover crops cohabiting vineyards, such as black oats. This study aimed to assess the effect of liming in reducing Cu toxicity in black oats grown in sandy soils. Samples of a Typic Hapludalf were collected at 0-20cm, dried and subjected to the addition of Cu (0 to 50Mg kg-1) and limestone (0, 1.5, and 3.0Mg ha-1). The soil was placed in a rhizobox and black oats were grown for 30 days. We assessed root and shoot dry matter production, copper (Cu), calcium (Ca) and magnesium (Mg) contents in the tissues; Cu content in the root symplast and apoplast, as well as Cu, carbon and pH values in the rhizosphere and bulk soil. Liming reduced Cu toxicity in black oats. Cu was preferentially accumulated in the roots, mostly in the apoplast, which may be the result of a plant tolerance mechanism to prevent the transport of Cu to the shoots.

RESUMO: Solos cultivados com videiras possuem alto teor de cobre (Cu) disponível, que pode ser tóxico às plantas de cobertura do solo que coabitam vinhedos, como a aveia preta. O estudo objetivou avaliar o efeito da calagem na redução da toxidez por Cu em plantas de aveia preta cultivadas em solo arenoso. Amostras de um Argissolo Vermelho foram coletadas na camada de 0-20cm, secas e submetidas à adição de duas doses de Cu (0 e 50Mg kg-1) e três de calcário (0, 1,5 e 3,0Mg ha-1). O solo foi acondicionado em rhizobox e submetido ao cultivo de aveia preta durante 30 dias. Avaliaram-se a produção de matéria seca das raízes e da parte aérea, o teor de cobre (Cu), cálcio (Ca) e magnésio (Mg) nos tecidos; o teor de Cu no simplasto e apoplasto das raízes, e os teores de Cu, de carbono e valores de pH no solo rizosférico e não rizosférico. A aplicação de calcário reduziu a toxidez por Cu na aveia preta. O Cu foi preferencialmente acumulado nas raízes, especialmente no apoplasto, o que pode ser resultado de mecanismo de tolerância das plantas para evitar o transporte de parte do elemento para a parte aérea.