Effect of temperature on the electro-oxidation of ethanol on platinum

We present in this work an experimental investigation of the effect of temperature (from 25 to 180 ºC) in the electro-oxidation of ethanol on platinum in two different phosphoric acid concentrations. We observed that the onset potential for ethanol electro-oxidation shifts to lower values and the reaction rates increase as temperature is increased for both electrolytes. The results were rationalized in terms of the effect of temperature on the adsorption of reaction intermediates, poisons, and anions. The formation of oxygenated species at high potentials, mainly in the more diluted electrolyte, also contributes to increase the electro-oxidation reaction rate.

Thermodynamic study of the solubility of triclocarban in ethanol + propylene glycol mixtures

By using the van't Hoff and Gibbs equations the apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for triclocarban in ethanol + propylene glycol mixtures were evaluated from solubility data determined at temperatures from (293.15 to 313.15) K. The drug solubility was greatest in the mixture with 0.60 in mass fraction of ethanol and lowest in neat propylene glycol at almost all the temperatures studied. Non-linear enthalpy-entropy compensation is found indicating apparently different mechanisms of the solution process according to the mixtures composition.

Solution thermodynamics of methocarbamol in some ethanol + water mixtures

Apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of solution and mixing, for methocarbamol in ethanol + water mixtures, were evaluated from solubility data determined at temperatures from 293.15 K to 313.15 K and from calorimetric values of drug fusion. The drug solubility was greatest in the mixtures with 0.70 or 0.80 mass fraction of ethanol and lowest in neat water across all temperatures studied. Non-linear enthalpy-entropy compensation was found for the dissolution processes. Accordingly, solution enthalpy drives the respective processes in almost all the solvent systems analyzed.

Use of sorghum straw (Sorghum bicolor) for second generation ethanol production: pretreatment and enzymatic hydrolysis

Agronomic biomass yields of forage sorghum BRS 655 presented similar results to other energy crops, producing 9 to 12.6 tons/ha (dry mass) of sorghum straw. The objective of this study was to evaluate the lignocellulosic part of this cultivar in terms of its potential in the different unit processes in the production of cellulosic ethanol, measuring the effects of pretreatment and enzymatic hydrolysis. Three types of pre-treatments for two reaction times were conducted to evaluate the characteristics of the pulp for subsequent saccharification. The pulp pretreated by alkali, and by acid followed by delignification, attained hydrolysis rates of over 90%.

Advances in ethanol reforming for the production of hydrogen

Catalytic steam reforming of ethanol (SRE) is a promising route for the production of renewable hydrogen (H2). This article reviews the influence of doping supported-catalysts used in SRE on the conversion of ethanol, selectivity for H2, and stability during long reaction periods. In addition, promising new technologies such as membrane reactors and electrochemical reforming for performing SRE are presented.

Amphoteric behavior of di-2-pyridyl ketone benzoylhydrazone in ethanol-water mixtures

The ligand di-2-pyridyl ketone benzoylhydrazone (DPKBH) is widely used for the determination of transition metal ions in environmental samples. Due to its low solubility in water it is used in aqueous-ethanol (1:1) solvent and for higher sensitivity the pH must be properly adjusted. The properties of DPKBH solutions must be known at different ethanol-water percentages in order to achieve higher sensitivity and/or selectivity for metal analysis. The acid-base behavior of this reagent in aqueous-ethanol solvent and the dissociation/ionization constants (pK1 and pK2) of DPKBH have been determined in different aqueous-ethanol solvent mixtures (10, 20, 30 and 50 % V/V of ethanol) from potentiometric titrations at 25.0 ± 0.1° C. As the amount of ethanol increases from 10 to 30% the pK1 and pK2 values increased, but they decreased in 50% of the organic solvent. The results are correlated with the medium composition and its effects.

Effect of alcohol concentration and electrode composition on the ethanol electrochemical oxidation

The electrochemical oxidation on platinum and platinum rhodium bimetallic electrodes was studied by Differential Electrochemical Mass Spectrometry for several ethanol concentrations in solution. It is found that increasing the ethanol concentration the production of the partially oxidized products (acetaldehyde) increases as the concentration increases. On the other hand, addition of 25% at. of rhodium increases the full oxidation to CO2. Another interesting result observed is a correlation between the intensity of the dehydrogenations peak at 0.3 V vs. RHE and the CO2 yield for the different ethanol concentration studied.

Adsorption of hidrogen peroxide on the surface of silica - titania mixed oxide obtained by the sol-gel processing method

This work describes the sol-gel mixed oxide SiO2/TiO2 property, ST, as prepared, and submitted to heat treatment a 773 K, STC. SEM and EDS images show, within magnification used, a uniform distribution of the TiO2 particles in SiO2/TiO2 matrix. Both, ST and STC adsorb hydrogen peroxide on the surface and through EPR and UV-Vis diffuse reflectance spectra, it was possible to conclude that the species on the surface is the peroxide molecule attached to the Lewis acid site of titanium particle surface, alphaTi(H2O2)+. As the material is very porous, presumably the hydrogen peroxide molecule is confined in the matrix pores on the surface, a reason why the adsorbed species presents an exceptional long lived stability.

Production of biodiesel from babassu oil using methanol-ethanol blends

Maranhão state in Brazil presents a big potential for the cultivation of several oleaginous species, such as babassu, soybean, castor oil plant, etc... These vegetable oils can be transformed into biodiesel by the transesterification reaction in an alkaline medium, using methanol or ethanol. The biodiesel production from a blend of these alcohols is a way of adding the technical and economical advantages of methanol to the environmental advantages of ethanol. The optimized alcohol blend was observed to be a methanol/ethanol volume ratio of 80 % MeOH: 20 % EtOH. The ester content was of 98.70 %, a value higher than the target of the ANP, 96.5 % (m/m), and the biodiesel mass yield was of 95.32 %. This biodiesel fulfills the specifications of moisture, specific gravity, kinematic viscosity and percentages of free alcohols (methanol plus ethanol) and free glycerin.

Potential of adjuvants to reduce drift in agricultural spraying

The reduction of pesticide spraying drift is still one of the major challenges in Brazilian agriculture. The aim of this study was to evaluate the potential of different adjuvant products, such as surfactants, drift retardants, mineral oil and vegetable oil for reducing drift in agricultural spraying. The experiment consisted of quantifying drift of sprayings of 18 adjuvants dissolved in water under controlled conditions in a wind tunnel. Tests were performed in triplicates with spraying nozzles type Teejet XR8003 VK, pressure of 200kPa and medium drops. Solutions sprayed were marked with Brilliant Blue dye at 0.6% (m v-1). The drift was collected using polyethylene strips transversally fixed along the tunnel at different distances from the nozzle and different heights from the bottom part of the tunnel. Drift deposits were evaluated by spectrophotometry in order to quantify deposits. The adjuvants from chemical groups of mineral oil and drift retardant resulted in lower values of drift in comparison with surfactants and water. The results obtained in laboratory show that the selection of appropriate class and concentration of adjuvants can significantly decrease the risk of drift in agricultural spraying. However, the best results obtained in laboratory should be validated with pesticide under field conditions in the future.

Effect of working pressure at different spray nozzles on drift quantification in wind tunnel

Each year, there is an increase in pesticide consumption and in its importance of use in the large-scale agricultural production, being fundamental the knowledge of application technology to the activity success. The objective of the present study was to evaluate the influence of working pressure on the drift generated by different spray nozzles, assessed in wind tunnel. The treatments were composed of two spray nozzles AXI 110015 and AXI 11002 with pressure levels of 276 and 414 kPa. The spray solution was composed by water and NaCl at 10%. The applications were conducted at wind speed of 2.0 m s-1, being the drift collected at 5.0; 10.0 and 15.0 m away from the spray boom and at heights of 0.2; 0.4; 0.6; 0.8 e 1.0 m from the tunnel floor. To both spray nozzles, the greatest drift was collected at the smallest distance to the spray-boom and at the lowest height. The AXI 11002 nozzle gave a smaller drift relative to the AXI 110015 nozzle for the two tested pressures and for all the collection points. Regardless of the nozzle, a rise in the working pressure increases the spray drift percentage at all distances in the wind tunnel.

Spray adjuvant characteristics affecting agricultural spraying drift

This study defined the main adjuvant characteristics that may influence or help to understand drift formation process in the agricultural spraying. It was evaluated 33 aqueous solutions from combinations of various adjuvants and concentrations. Then, drifting was quantified by means of wind tunnel; and variables such as percentage of droplets smaller than 50 μm (V50), 100 μm (V100), diameter of mean volume (DMV), droplet diameter composing 10% of the sprayed volume (DV0.1), viscosity, density and surface tension. Assays were performed in triplicate, using Teejet XR8003 flat fan nozzles at 200 kPa (medium size droplets). Spray solutions were stained with Brilliant Blue Dye at 0.6% (m/ v). DMV, V100, viscosity cause most influence on drift hazardous. Adjuvant characteristics and respective methods of evaluation have applicability in drift risk by agricultural spray adjuvants.

KNOWLEDGE ON ADJUVANT PROPERTIES, DISPOSAL OF PESTICIDERESIDUES AND SPRAY DRIFT OCCURRENCE IN THE STATE OF MATO GROSSO

ABSTRACT This paper aimed at investigating the knowledge level of people working on pesticide spraying activities concerning spray adjuvant properties, as well as collecting information on disposal locations for residues from internal spray tank cleaning, and finally the understanding of pesticide spray drift occurrence in the state of Mato Grosso, Brazil. The information was gathered through a questionnaire answered by participants of a rural extension program in application technology located in nineteen grain and fiber producing regions of Mato Grosso state. Among the mentioned adjuvants, 49.0% belonged to the mineral oil class and 17.9% of participants did not know the functions performed by such products. In addition, 58.5% of the participants discarded residues into the field. Among the participants who answered the question about spray drift occurrence causes, 54.1% indicated problems relating to inadequate weather conditions. In conclusion, there is a lack of knowledge on adjuvant functions, besides of inappropriate residue disposal in the state of Mato Grosso. Spray drift was referred as a problem; however, most of participants were not able to discuss the causes of these losses.

Glyphosate drift affects arbuscular mycorrhizal association in coffee

Mycorrhizal association promotes better survival and nutrition of colonized seedling on field, and consequently, increasing of productivity. However, the weed management can interfere on this association, due to incorrect use of glyphosate. This work has assessed the effects of glyphosate drift on the growth and nutrition of arabica coffee plants (Catuaí Vermelho - IAC 99) colonized with arbuscular mycorrhizal fungi (AMF). The experiment was conducted in 2 x 5 factorial scheme, and included inoculated and non-inoculated plants, and five glyphosate subdoses (0.0, 57.6, 115.2, 230.4, and 460.8 g ha-1 of glyphosate), in randomized blocks with five replication. The inoculation was carried during the greenhouse phase of seedlings production with a mixture of Rhizophagus clarus and Gigaspora margarita, and after to transplanting, when the plants had seven pairs of leaves, glyphosate subdoses were applied. The product caused intoxication in up to 60% of non-inoculated and 45% on inoculated plants, when the highest dose of 460.8 g a.e. ha-1 was applied. A negative effect was noted on the growth and phosphorus content of coffee plants, this effect increased depending on glyphosate subdose, but regardless of inoculation. Glyphosate drift reduces the growth and nutrition of plants colonized by species of AMF and native fungi, negatively affecting root colonization of plants treated.

GLYPHOSATE DRIFT IN EUCALYPTUS PLANTS

ABSTRACTWith the present study we aim to assess the damage caused to Eucalyptus plants exposed to glyphosate drift in different canopy portions. The drift simulation was carried out through application of 1,080 g ha-1 of glyphosate in five canopy portions (0, 25, 50, 75 and 100% of the low branches), in four areas of cultivation. Areas I and II, plants with 0.91 and 2.98 m, and height of canopy drift exposition of 0.30 and 1.0 m, respectively. In areas III and IV both cultivations were 8.15 m high, varying the height of drift exposition between 2.0 and 2.5 m, respectively. At 30 and 480 days after application (DAA), the survival rate was assessed, and at 300 and 480 DAA diameter at breast height (DBH), height, volume and their respective increment were determined. The medium annual increment (MAI) was determined at 480 DAA. Area I, in which the plants were 0.91 m high, we observed that treatment with 100% of the low branches exposed to drift led to stand reduction of the plants around 18.75 and 38.19% at 30 and 480 DAA, respectively. Areas I and II showed reduction in plant growth in height and DBH, wood volume and MAI, to the extent that there was an increase in the portion of canopy exposed to glyphosate drift. However, in areas III and IV, in which 8.15 m height plants were found, no changes were verified for the evaluated characteristics, regardless of the portion of canopy exposed to glyphosate drift.