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.

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.

New bifunctional asymmetric catalysts containing a Lewis acid Ti(IV)/V(IV) and a Lewis base were developed and applied to the catalytic asymmetric cyanosilylation of benzaldehyde and oxidation of sulfides to chiral sulfoxides. The products were obtained with moderate to low enantiomeric excess.

Se han desarrollado nuevos catalizadores asimétricos bifuncionales que contienen un ácido de Lewis y una base de Lewis, y se han aplicado a las reacciones asimétricas catalíticas de cianosililación de benzaldehído y oxidación de sulfuros a sulfóxidos quirales. Los productos se obtuvieron con excesos enantioméricos de moderados a bajos.

A library of chiral Schiff base ligands was synthesized from aromatic aldehydes and chiral amino alcohols. These ligands were then screened as catalysts in the asymmetric ring opening of meso-cyclohexene epoxide with phenyllithium to give (1S,2R)-phenylcyclohexanol in 9-67% ee.

Se ha sintetizado una biblioteca de ligandos quirales tipo base de Schiff a partir de aldehídos aromáticos y aminoalcoholes quirales. Se midió la capacidad catalítica de estos ligandos en la apertura asimétrica del anillo de meso-epóxido de ciclohexeno con fenillitio para dar (1S,2R)-fenilciclohexanol con 9-67% ee.

Chiral cyanohydrins were synthesized from anisaldehyde and trimethylsilylcyanide catalyzed by a chiral Schiff-base titanium complex. Cyanohydrins were converted into chiral the ß-hydroxyamides, (R)-Tembamide and (R)-Aegeline.

Se sintetizaron cianohidrinas quirales a partir de anisaldehído y cianuro de trimetilsililo por medio de la reacción catalizada con un complejo de titanio y una base de Schiff quiral. Las cianohidrinas fueron convertidas a las ß-hydroxyamidas quirales, (R)-Tembamida y (R)-Aegelina.