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.

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.

In this work the synthesis of amphiphilic hydrogels is reported, based on methacrylic acid derivatives with hydrophobic spacers of aliphatic type (1, 3, 5, 9 and 10 methylene units). The prepared hydrogels show critical pH values for deswelling-swelling transition in accordance with the aliphatic spacer: the longer the aliphatic spacer the higher the critical pH. The critical pH corresponds well with the pKa shifts expected as effect from the aliphatic spacer when the number of methylene units goes from 1 to 5. However, when the number of methylene units is 9 and 10, the observed critical pH is higher than that expected from the aliphatic spacer influence. Additional hydrophobic interactions could be responsible for the observed behavior.

En este trabajo se reporta la síntesis de hidrogeles anfifílicos, derivados del ácido metacrílico con espaciadores hidrofóbicos tipo alifático de diferente longitud (1, 3, 5, 9 y 10 metilenos). Los hidrogeles obtenidos mostraron un pH crítico de contracción-hinchamiento en función del espaciador alifático: a mayor longitud del espaciador alifático mayor pH crítico. El pH crítico coincide con el cambio de pKa por efecto del espaciador alifático cuando el número de metilenos va de 1 a 5. Sin embargo, cuando el espaciador contiene 9 y 10 metilenos el pH crítico está por arriba del cambio de pKa por efecto del espaciador. Interacciones hidrofóbicas adicionales pueden ser responsables de este comportamiento.