Influence of the formulation variables on the viscosity of anionic surfactant-oil-water emulsions.

Phase transition and viscosity behavior of emulsified systems were studied after modifying their physicochemical formulation. Effects of concentration and nature of salts and n-alcohols, and water/oil relation on the rheological properties of emulsions were also studied. Pre-equilibrated systems were emulsified according to an agitation procedure, and the viscosity (cP) was measured at different shear rates ranging from 1 to 300 s-1. The phase behavior, as well as the emulsion type based on electrolytic conductivity, was observed. Several interpretations of the flow and viscosity curves of emulsions were made through the estimation of rheological parameters such as consistency index "k" and behavior index "n"

Síntesis asistida por microondas de derivados acilados de lignina de diferentes masas molares con posible actividad superficial.

Lignins of different molar masses were esterified using microwave radiation and the surface activity of the derivatives obtained were evaluated.The lignin was fractionated by ultrafiltration using ceramic membranes of 15 and 8 kDa. Succinic anhydride and glutaric anhydride were used to modify the lignin. The surface activity of the derivatives was evaluated by measuring the surface tension. FTIR spectra showed the incorporation of carboxylic acid-ester groups in lignin. Esterified products decreased the surface tension between 10-20% with respect to the original lignin, and this effect was greater for glutaric anhydride esterified products at high concentrations. The incorporation of new acid-ester groups in the lignin structure provides a higher amphiphilic character to lignin, due to the presence of new polar functional groups that allow the adsorption on the surface minimizing the attraction forces within the liquid.Se esterificaron ligninas de diferentes masas molares empleando radiación microondas y se evaluó la actividad superficial de los derivados obtenidos. La lignina se fraccionó por ultrafiltración utilizando membranas cerámicas de 15 y 8 KDa. Se emplearon anhídrido succínico y anhídrido glutárico para modificar la lignina. La actividad superficial de los derivados se evaluó midiendo la tensión superficial. Los espectros FTIR mostraron la incorporación de los grupos éster-ácido carboxílico en la lignina. Los productos esterificados disminuyeron la tensión superficial entre un 10-20% con respecto a la lignina original, siendo este efecto mayor para los productos esterificados con anhídrido glutárico a altas concentraciones. La incorporación de los nuevos grupos éster-ácido en la estructura lígnica le proporciona un mayor carácter anfifílico, debido a la presencia de nuevos grupos funcionales polares que permiten la adsorción en la superficie minimizando las fuerzas de atracción en el seno del líquido

Estudio del coeficiente de reparto de ácidos carboxílicos grasos en sistemas modificados heptano/agua

The use of fatty acids (FAs) as amphiphiles is very important because they have a behaving similar to surfactants. The formulation for the preferential partition of these species was studied by varying the amount of salt at constant acid concentration. As the salt concentration increases, a Winsor I→III→II transition is observed for all the systems studied. Furthermore, the electrolyte concentration required to obtain the optimum formulation varies inversely with the chain length of the acid. The partition coefficient of the surfactant allows one to obtain thermodynamic information on the acid transfer process between the phases of the system

Comportamiento de agregación de noveles surfactantes de par iónico: Aggregation behavior of novel ion pair surfactants

Los ácidos alquilcarboxílicos pueden dar origen a la formación de una especie iónica con características anfifílicas que disminuye la tensión superficial de un sistema agua/aire. El tipo de contraión de estas especies juega un papel fundamental en las propiedades superficiales del compuesto. Se preparó una novedosa clase de surfactantes de par iónico (SPI) por neutralización de cantidades equimolares del ácido carboxílico con una base de tipo ciclohexilamina (cHACn) bajo condiciones suaves de reacción. Se estudió el comportamiento de agregación por tensión superficial. Los compuestos obtenidos disminuyeron la tensión superficial presentando baja concentración micelar crítica (CMC) y por tanto una mayor actividad superficial. La CMC de todos los compuestos estudiados disminuyó con la longitud de la cadena alquílica aniónica (n).  Palabras clave: ácidos alquilcarboxílicos, surfactantes de par iónico, comportamiento de agregación, tensión superficial. ABSTRACT The alkylcarboxylic acids can give origin to the formation of ionic species with amphiphilic characteristics that decreases the surface tension of a water/air system. The type of counterion of these species plays a fundamental paper in the surface properties of the compound. Novel class ion pair surfactants (IPS) were prepared by neutralization of equimolar amounts of carboxylic acid with a base of type cyclohexylamine (cHACn) though mild reaction conditions. The aggregation behavior through surface tension was studied. The compounds obtained reduced the surface tension presenting low critical micelar concentration (CMC) and therefore a greater surface activity. The CMC of all compounds studied decreased with the length of the anionic alkyl chain (n).  Key words: Alkylcarboxylic acids, ion pair surfactant, aggregation behavior, surface tension

Utilization of industrial by-product fungal biomass from Aspergillus niger and Fusarium culmorum to obtain biosorbents for removal of pesticide and metal ions from aqueous solutions

In this work, Aspergillus niger and Fusarium culmorum cell wall by-products were chosen as microbial sources for chitin and chitosan production. Both polysaccharides were characterized by FTIR and C-13-CPMAS NMR, but GPC analysis was only performed for chitosan. SEM-EDX analysis was performed to fungal chitosan loaded with metal ions. Chitosan extracted from both fungus had low to medium molecular weight (Mw) and degree of deacetylations (DD) ranging from 65.7-83.3%. Fungal chitosan samples were intended to be used for bioremediation applications. For this purpose, two independent absorption experiments regarding pesticide Dimethoate (DM) and heavy metal ions (Al(III), As(III), Cd(II), Cu(II), Mg(II), Mn(II), Pb(II), Zn(II), Fe(II)) in a complex mixture were carried out. An experimental design considering the solution pH, contact time and chitosan physicochemical properties (DD) were performed. The highest percentage of dimethoate pesticide and selected metal ions absorption was obtained with highest DD chitosan, the contact time of 24 h, pH 6 for metals and pH 4 for pesticide, repectively. Molecular dynamics simulation studies allowed to analyze at the molecular level the chitosan-DM interaction. A higher number of h-bonds were identified as the main interactions that stabilize the affinity of the chitosan-DM complexes. Based on our results, we suggest the use of a multipurpose fungal chitosan system for water bioremediation