Use of water in the biodiesel purification process: optimization by controlling electrical properties of effluent

La producción sustentable de biodiesel requiere la optimización del consumo de agua. Este es un factor clave que debe tenerse en cuenta en la etapa de diseño y en la operación de las plantas. El impacto ambiental y la calidad del producto final dependen críticamente del correcto diseño del proceso de purificación y del control del mismo durante la producción. En plantas pequeñas y medianas el consumo de agua empleado respecto al volumen de biocombustible a purificar llega al 100% o 150%; la proporción cae al 35% en instalaciones grandes, en que se recupera la mayor parte del agua. Los efluentes de la producción de biodiesel consisten principalmente en el agua de lavado, que contiene cantidades variables de alcohol y catalizador. En consecuencia, un tratamiento deficiente de los efluentes involucra riesgos ambientales debidos a la contaminación de aguas subterráneas y superficiales, y sistemas de desagüe. En este trabajo se analiza la optimización del uso de agua en la producción de biodiesel, en particular durante la etapa de purificación. Se miden las propiedades eléctricas de los efluentes (permitividad, conductividad y factor de disipación), como función de la frecuencia y la temperatura. La reducción progresiva de los valores medidos constituye una indicación de la remoción del alcohol y los restos de catalizador del producto en las sucesivas etapas de lavado. Esto permite controlar el grado de avance del proceso y verificar su finalización. La purificación se considera adecuada cuando los valores medidos en los efluentes de la última etapa de lavado son cercanos a los del agua limpia empleada. Asimismo, los apartamientos respecto de los valores óptimos de los parámetros se detectan por comparación con valores de referencia. A diferencia de otras técnicas (cromatografía, espectrofotometría, etc.), las mediciones de propiedades eléctricas son rápidas, eficientes y económicas, y se adaptan bien a los sistemas de control automáticoSustainable production of biodiesel requires the optimization of water use. This is a key issue that must be considered at the design stage and during plant operation. The environmental impact and the quality of the final product depend critically on the correct design of the purification process and its control during production. In plants of small and medium size water consumption may reach 100% to 150% of the volume of the product to be purified; this ratio falls to 35% in large installations, where most of the water is recovered. Effluent from biodiesel production consists mainly of water from the washing steps, containing variable amounts of alcohol and catalyst. In consequence, the inadequate treatment of effluent involves serious environmental risks due to contamination of sewer systems and surface and underground water. In this work the optimization of water use in biodiesel production is analyzed, particularly during the purification stage. Electrical properties of effluent (permittivity, conductivity and dissipation factor) are measured as a function of frequency and temperature. The steady reduction of the measured values in the effluent indicates the removal of alcohol and catalyst remaining in the product at the successive washing steps. This makes possible to monitor the advance of the process and verify its completion. The purification is regarded as adequate when the measured values in the effluent of the last washing stage are close to those of the clean water used. Also, deviations from optimum parameter values are detected by comparison to reference values. Compared with other techniques (chromatography, spectrophotometry, etc.), electrical properties measurements are fast, efficient and economical, and adapt well to automated control systems.Comité de Medio Ambient

Required Hydrophilic-Lipophilic Balance values of octyldodecanol from emulsion stability tests and relative dielectric permittivity measurements

Although octyldodecanol has been used for several decades as an ingredient for emulsions, no required Hydrophilic-Lipophilic Balance (HLB) values for this alcohol were found in the literature. The purpose of this paper is to present the results of the experimental determination of the required HLB values, from emulsion stability tests and from low-frequency relative dielectric permittivity measurements. The required HLB values obtained from emulsion stability tests for oil-in-water and water-in-oil emulsions are 11.2 and 5.9, respectively. By relative dielectric permittivity measurements, the required HLB value obtained for oil-in-water emulsions was 10.9 ± 0.4, in agreement with the results from emulsion stability tests.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Solubility and stability studies of benzoyl peroxide in non-polar, non-comedogenic solvents for use in topical pharmaceutical formulation developments

Non-irritant, non-comedogenic and non-polar emollients were pre-selected for determinations of relative dielectric permittivity and solubility of benzoyl peroxide (BP). Those solvents capable of solubilizing BP in concentrations commonly utilised in topical formulations (between 1 and 10 %) were taken into account for stability studies. The developed pre-formulations were also studied for acute irritation both clinically and instrumentally. Even though the solubility of BP in the solvents studied had relatively low values; in some cases, such as with caprylic/capric triglyceride (CapCap) and dicaprylyl carbonate (DicCar) it has been possible to obtain acceptable concentrations of BP from a therapeutic viewpoint (19.9 and 19.5 mg/mL, respectively). Two BP pre-formulations (PBCapCap and PBDicCar) with enhanced stability and with the capability to decrease adverse application site reaction by maintaining moisture in the stratum corneum were developed with potential application in topical formulations of BP with solvents of low relative dielectric permittivity (CapCap and DicCar, respectively).Colegio de Farmacéuticos de la Provincia de Buenos Aire

Propagation of Gaussian beams through active layers

Knowledge of propagation, transmission and reflection properties of space- and time-limited beams is relevant to the classical description of electromagnetic field modes in laser and other optoelectronic devices. For many reasons, Gaussian beams have been the most widely studied; for instance, they correspond to the fundamental mode in cylindrical or rectangular resonators, and they are often desirable at the output of amplifiers. To describe the behavior of beams with a Gaussian amplitude profile, the usual method consists of making an approximation in Maxwell equations, such that the solution of the approximate equations is a Gaussian beam. In this work we propose a different method to study Gaussian beams in active media, describing the beam by a continuous spectrum (spatial or temporal) of plane waves. We consider active media far from saturation, i.e. the gain is independent of the electric field amplitude. As a first step in the study of propagation, transmission and reflection of pulses through thin layers of active media, we analyze the properties of the transmitted beam in the case of a thin slab with gain between two isotropic transparent semi-infinite media, assuming normal incidence of a two-dimensional, space- or time-limited gaussian beam.Fil: Vázquez, Verónica. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; ArgentinaFil: Fernández, Juan Carlos. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; ArgentinaFil: Garea, María T.. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; ArgentinaFil: Matteo, Claudia Leda. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Perez, Liliana Ines. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Sorichetti, Patricio A.. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; Argentin