Membrane fouling by natural organic matter (NOM) is a major problem in ultrafiltration (UF) water treatment. The objective of this study was to evaluate the effects of operations modes on natural organic matter fouling, rejection and flux decline during UF. A comparison of constant pressure and constant flux tests confirmed that modest constant flux provided the most beneficial conditions. As general observation hydrophilic membranes were less prone to NOM fouling.

Waste glass from plasma display panel, PDP, is usually disposed of in a landfill, without recycling. The recovery of the PDP glass was investigated to contribute to the sustainable development use of this waste, once the coatings were removed from the glass in order to minimize the generation of hazardous waste. The process was designed on a laboratory level for the recovery of PDP waste glass. The chemical procedure of recovering residual glass was investigated to eliminate the coatings from the glass using corrosive wet scrubbing. A previous study was performed about the percent of removal of the coatings by treatment with five acids and two bases. It was determined that the aqua regia (HNO3: HCl, 1:3) and sodium hydroxide (NaOH) are the best removal agents of the coatings in combination with ultrasonic treatment. The parameters that were evaluated to determine the optimum condition of removal are the concentration of the acid and the base, the temperature, the volume of the dissolution and the time of the wash. Two washing stages were established: first the treatment with aqua regia, and second the treatment with sodium hydroxide; the used procedure removed nine of twelve layers, which corresponds to 97% of the coatings weight. The recovered glass has sufficient quality to be used in other production process. The processes of removal, the treatment of 261 samples of PDP glass and the results, are discussed in the following article.

Se investigó la recuperación del vidrio de pantallas de plasma (plasma display panel, PDP) para contribuir al desarrollo sustentable de la utilización de residuos, al remover las capas de los recubrimientos del vidrio y minimizar los residuos peligrosos generados. Se propone un nuevo método para el proceso a nivel laboratorio de la recuperación del vidrio PDP residual. Se investigó sobre el procedimiento químico de recuperación del vidrio PDP residual, eliminando las capas de recubrimientos que contiene el vidrio mediante lavados corrosivos con baño ultrasónico. Se realizó un estudio previo sobre el porcentaje de remoción de las capas mediante el tratamiento con cinco ácidos o dos bases. Se determinó que el agua regia (HNO3:HCl, 1:3) e hidróxido de sodio (NaOH) son los mejores agentes removedores de capas vítreas. Los parámetros evaluados para determinar las mejores condiciones de remoción son el cambio de concentración del ácido y de la base, la temperatura, el volumen de disolución y el tiempo de lavado. Se establecieron dos etapas de lavado: primer tratamiento con agua regia y segundo tratamiento con hidróxido de sodio; mediante el procedimiento utilizado se removieron nueve de doce capas, el cual corresponde al 97 % en peso de los recubrimientos. El porcentaje de vidrio recuperado tiene la calidad suficiente para su aprovechamiento en la manufactura de materiales vítreos. El proceso de remoción, el tratamiento de 261 muestras de vidrio PDP y los resultados, son discutidos en el presente artículo.

The covalent functionalization of multiwall carbon nanotubes (MWCNT) and its characterization techniques are reported. MWCNT were functionalized with tert-butyldiazoacetate to give methano-bridged ester group. Functionalized carbon nanotube by ester and its hydrolyzed carboxylic acid were characterized by high resolution electron microscope techniques, scanning electron microscopy (SEM), transmission electron microscopy (TEM) to study the shape a structure and fast Fourier transform infrared (FT-IR) to evaluate types of binding.

Se reporta un método de funcionalización covalente para nanotubos de carbono de multicapas y su respectiva caracterización de la superficie. Los nanotubos de carbono con un puente de metano y grupos éster es funcionalizado con diazoacetato de terbutilo. El material funcionalizado se caracterizó por técnicas de microscopía electrónica de alta resolución en sus modalidades de barrido y trasmisión, también se uso espectroscopia de infrarrojo con transformadas de Fourier para evaluar los enlaces generados.

Membranas bipolares foram preparadas pela junção de membranas de troca catiônica e aniônica. Para a preparação da camada seletiva a cátions, soluções aquosas de PVA [poli(vinil álcool)] e PASA [poli(sódio anatolesulfonato)], em que a razão PVA/PASA foi modificada para o controle da densidade de carga da membrana, foram preparadas para produzir membranas carregadas negativamente. Estas membranas foram tratadas a 100 ºC por 45 min e reticuladas em solução aquosa contendo 10% de Na2SO4, 1,5% de H2SO4 e 0,5% de glutaraldeído, a fim de controlar a quantidade de água no gel das membranas. As camadas seletivas a ânions foram preparadas pela dispersão de uma solução de PVA e PDDAB [poli(brometo de dialildietilamônio)] em DMF, em que a razão PVA/PDDAB foi modificada para o controle da densidade de carga na membrana. A resistência elétrica de membranas bipolares preparadas por esta metodologia aumentou ligeiramente, enquanto a seletividade diminuiu e sua perme-seletividade não mudou com o pós-tratamento ácido ou alcalino.

Bipolar membranes (BMP) were prepared by bonding together separate anion and cation exchange membrane. For the preparation of the cation selective layer, aqueous solution of PVA [poly(vinyl alcohol)], and PASA [poly(anetholesulfonic acid sodium salt)], where the ratio of PVA/PASA was changed for the control of the membrane charge density, were cast for negatively charged membranes. These membranes were annealed at 100 ºC for 45 min and cross-linked in an aqueous solution containing 10% Na2SO4, 1.5% H2SO4, and 0.5% glutaraldehyde in order to control water content of the gel membranes. The anion selective layers were prepared by dispersing a solution of PVA and PDDAB [poly(diallyldiethylammonium bromide)] in DMF, where the ratio of PVA/PDDAB was changed for the membrane charge density control. The electrical resistance of BMP formed by this methodology was slightly increased while the selectivity decreased, while their permselectivity did not change with the acid or alkaline post-treatment.

This paper reports the synthesis and characterization of asymmetric ultrafiltration membrane made from recycled polystyrene foam (PS) with different additives and polyvinylpyrrolidone (PVP). The polystyrene is currently employed as packing, in fabrication of glasses and dishes. The recycled polystyrene is inexpensive and easy to acquire and, at less in Mexico, not a conscience exists of recycled. The membranes where prepared by phase inversion process from casting solution containing polystyrene as polymer, l-methyl-2-pyrrolidone (NMP) as solvent, and polyethylene glycol (PEG) of different molecular weights and dioctyl phthalate (DOP) as additives. The membranes where characterized in terms of pure water permeation (PWP), molecular weight cut off (MWCO), flux and membrane morphology. The results revealed that the addition of PEG with high molecular weights, produce membrane with higher pure water permeation. The presence of additives affects the surface roughness and membrane morphology.

Recently, a renewed interest has emerged in reformulated and alternative fuels as a way to control emissions and provide energy independence. Biodiesels (fatty acid methyl esters) derived from the transesterification of vegetable oils or animal fats with methanol are potential substitutes for petroleum-based diesel fuels. Compared with conventional diesel, biodiesel has the advantages of being biodegradable, renewable, non-toxic, and producing low emission of pollutants emissions (especially SOx). The biodiesel yield and its ester content were dependent on the type of vegetable oil used; both of these parameters decrease when the vegetable oil's acid value increased due to neutralization of the free fatty acids in the oil. The work that we present here describes a process for the preparation of biodiesel using blended commercial oils and lithium hydroxide as a catalyst. The viscosity, peroxide and acid value of biodiesel complied with specifications established by the EU (European Union) for this type of fuel.

En la actualidad existe gran interés en reformular los combustibles, como una alternativa para controlar las emisiones y satisfacer las demandas energéticas. El biodiesel se obtiene por transesterificación de aceites vegetales o grasas animales con metanol y son los substitutos potenciales para diesel derivado del petróleo. Comparado con diesel convencional, el biodiesel tiene las ventajas de ser biodegradable, renovable, no tóxico, y generar emisiones bajas de contaminantes (especialmente SOx). El rendimiento de Biodiesel y contenido de éster dependen del tipo de aceite vegetal, ambos disminuyen cuando el número ácido del aceite vegetal aumenta debido a la neutralización del contenido libre de ácido graso en el aceite. La presente investigación se enfoca en la obtención de biodiesel a partir de mezclas comerciales de aceite comestible e hidróxido de litio como catalizador. La viscosidad, el valor del peróxido, y el número ácido estuvieron dentro de las especificaciones de la comunidad europea establecidas para el biodiesel.

This paper present a method to determine pore diameters and effective transport through membranes using a mixture of oligosaccharides. The results are compared with the Maxwell-Stefan equations. The partition coefficients of the solutes are a function of the pore diameter according to the Ferry equation. Thus, with the pore diameter as the only unknown parameter, rejection is described and the pore diameter is obtained by a Marquardt-Levenberg optimization procedure.

Se presenta un método para determinar el diámetro de poro y transporte efectivo de masa a través de membranas, empleando una mezcla de oligosacáridos. Los resultados se comparan con la ecuación de Maxwell-Stefan. Los coeficientes de partición de los solutos son función del tamaño de poro, de acuerdo con la ecuación de Ferry. El diámetro de poro se determina como único parámetro desconocido, el rechazo y el diámetro de poro se obtienen mediante el procedimiento de optimización de Marquardt-Levenberg.

Ordinary polymeric membranes are hydrophobic in nature, thus hydrophobic polymeric membranes foul rapidly in water purification operations. A change in membrane surface properties can reduce fouling; this may be accomplished by increasing the hydrophilicity of the membrane surface, and by using a membrane with smaller pore size. The ultrafiltration membranes were prepared via phase inversion process in our laboratory, from polysulfone / polyvinylpyrrolidone (PS / PVP). The basic characteristics of these membranes like water permeability, water content and membrane selectivity were measured.

Las membranas poliméricas por naturaleza son hidrofóbicas, por tanto se ensucian rápidamente en operaciones de purificación de agua. Un cambio en las propiedades de las membranas puede reducir el ensuciamiento; esto se puede lograr al incrementar la hidrofilicidad de la membrana. Las membranas de ultrafiltración empleadas, se prepararon en nuestro laboratorio, por el método de inversión de fases, a partir de polisulfona/polivinilpirrolidona (PS / PVP). Se determinó la permeabilidad, contenido de agua, peso molecular límite, rugosidad superficial de las membranas y se estudio la sección transversal de las membranas