La Plata, Argentina


La Plata, Argentina
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Fernandez M.,CETMIC CCT la Plata | Curutchet G.,National University of San Martín of Argentina | Torres Sanchez R.M.,CETMIC CCT la Plata
Water, Air, and Soil Pollution | Year: 2014

In this study, the characterization and adsorption properties of montmorillonite (MMT) and organomontmorillonites with different surfactant/cationic exchange capacity (CEC) ratios (1 and 2) of tetradecyl trimethylammonium (TDTMA+) and hexadecyl trimethylammonium (HDTMA+) cations were evaluated. The particle apparent diameter, determined by laser and scanning electron microscopy showed aggregate formation, which varied with loading and cation length of the surfactant used. X-ray diffraction analysis revealed the formation of a pseudotrilayer arrangement of both surfactants in the interlayer space, FTIR showed the characteristic bands of the surfactants and micelle formations, and zeta potential determinations indicated neutral or negative surface charge values, except for sample obtained with one CEC concentration exchanged with HDTMA+ (HDTMA1-MMT) where a charge reversal to positive was found. Higher adsorption amounts of humic acid (HA) were found for HDTMA1-MMT and TDTMA1-MMT samples than for MMT sample, while the increase in the loading of both surfactants decreased the amounts of HA adsorbed could be assigned to a higher micelle formation and different packing density of alkyl chain, in the external surface. The correlation found between the total surface area and negative zeta potential values and the HA adsorption rate, within each surfactant, indicated the strong influence that these properties have on HA adsorption. © Springer International Publishing 2014.

Flores F.M.,CETMIC CCT La Plata | Gamba M.,CETMIC CCT La Plata | Sanchez R.M.T.,CETMIC CCT La Plata | Brendle E.,Adscientis | Brendle J.,CNRS Mulhouse Institute of Materials Science
Applied Clay Science | Year: 2016

The importance of fungicides uses to maintain healthy crops and reliable, high-quality yields poses environmental issues due to the water and soil contaminations. The montmorillonite is known as efficient adsorbent for many pesticides, while the organo modification enabled to use them in wider range of applications. In this study, the fungicide fludioxonil (FDX) was adsorbed on raw and organo-modified Patagonian montmorillonite. The effects of the organo treatment as well as the FDX adsorption on the surface properties were investigated by X-ray diffraction, microelectrophoresis and inverse gas chromatography. The importance of the organo treatment was revealed both for the changes in the surface properties (dispersive component of the surface energy, nanoroughness and surface acidity as well as zeta-potential) and for the adsorption of FDX as it enabled increase two times respect to the pristine montmorillonite. © 2016 Elsevier B.V.

Yapar S.,Ege University | Ozdemir G.,Ege University | Solarte A.M.F.,CETMIC CCT La Plata | Sanchez R.M.T.,CETMIC CCT La Plata
Clays and Clay Minerals | Year: 2015

Catanionic surfactant systems are used as drug-delivery vehicles and as nanocompartments in the formation of biomaterials and nanosized particles. Clay minerals are compatible with organic tissues and also have biomedical applications. The aim of the present study was to combine the properties of catanionic surfactants and clay minerals to obtain new materials with potential uses in medicine, wastewater treatment, and antibacterial applications. The surfactants chosen to make the catanionic surfactant were cetylpyridinium (CP) and lauroyl sarcosinate (SR), which interact strongly in aqueous media and cause specific aggregations such as ion-pair amphiphiles and needle- and leaf-like structures. Aside from the aqueous solution, new ternary systems are formed with different structures and properties through the addition of montmorillonite (Mnt). The surface and interlayer structures of the different Mnt-CP-SR samples prepared by using CP and SR in amounts equal to various ratios of cationic exchange capacity of the clay mineral were studied. They were also compared with the structured surfactant aggregates formed in aqueous media. The Mnt-CP-SR samples were subjected to X-ray diffraction (XRD), thermogravimetric analyses, and zeta-potential measurements to elucidate the interlayer- and external-surface structures. The XRD analyses showed the formation of a compact structure in the interlayer region resulting from the interaction between randomly oriented pyridinium and negatively charged SR head groups. The triple interactions among the Mnt surface, CP, and SR were more complex than the double interactions between the Mnt and cationic surfactant, and the CP played a dominant role in the formation of external and interlayer surface structures regardless of the amount and order of the addition of SR. The new findings support new applications for organoclays in the fields of biomedicine, remediation of polluted water, and nanocomposite materials. © 2015, Clay Minerals Society. All right reserved.

Bianchi A.E.,National University of La Plata | Fernandez M.,National University of La Plata | Pantanetti M.,CETMIC CCT La Plata | Vina R.,National University of La Plata | And 3 more authors.
Applied Clay Science | Year: 2013

In this work we investigate the microstructure and properties of organo-montmorillonites (OMts) synthesized by intercalation of a Patagonian Mt with different surfactant/CEC ratios (0.5, 1 and 2) of octadecyl trimethylammonium (ODTMA+) and hexadecyl trimethylammonium (HDTMA+) cations. X-ray diffraction (XRD) patterns showed that in all OMt samples d001 value increases with respect to raw Mt (1.258nm). Small angle and wide angle X-ray scattering (SAXS and WAXS) curves, particle apparent diameters (determined by laser), zeta potential values and scanning electron microscopy (SEM) images, showed the presence of assorted d001 values (which depend on storage conditions), aggregate formation and charge reversal (which varied with loading and cation length) for samples obtained with 1 and 2 CEC. However, for samples intercalated with 0.5 CEC, we found evidence of smaller aggregate formation, no charge reversal, and similar d001 and zeta potential values (both higher than those of Mt). Findings reported here will help attain better conditions to functionalize highly charged Mt making them suitable to be used as nanocomposite precursors for different applications. © 2013 Elsevier B.V.

Gamba M.,CETMIC CCT La Plata | Flores F.M.,CETMIC CCT La Plata | Madejova J.,Slovak Academy of Sciences | Sanchez R.M.T.,CETMIC CCT La Plata
Industrial and Engineering Chemistry Research | Year: 2015

To remove fungicide Imazalil (IMZ) (commercial formulation) from agricultural wastewater, adsorption was performed and compared among montmorillonite (Mt) and four organo-Mts (OMts), with different octadecyltrimethylammonium (ODTMA) loadings. The agglomerates size increase of OMts with respect to Mt found encourages the use of the former in agricultural wastewater treatment. Characterization of the OMts adsorbents by powder X-ray diffraction, infrared spectroscopy, and thermogravimetric analyses, indicated that ODTMA was present in the interlayer with diff erent molecular arrangements, a diminution of the thermal stability of the OMts and an increase of ODTMA loading being observed at the same time. Zeta potential measurements showed electric surface charge reversion from negative to positive when the surfactant loading exceeded 100% of the clay cation exchange capacity (CEC). The IMZ adsorption on the raw Mt showed high pH dependence and affinity toward the fungicide, while OMts showed best IMZ adsorption capacity at high IMZ concentrations inversely related with the ODTMA loading. The characterization of IMZ-adsorbed samples indicated that for IMZ-Mt the interaction between IMZH+ and the siloxane surface was electrostatic. For IMZ-OMt samples the presence of new XRD and FTIR peaks suggested different IMZ interlayer arrangements and direct interaction with the surface, respectively. Analysis of zeta potential measurements indicated synergetic effects between the ODTMA and IMZ molecules at the external surface. © 2015 American Chemical Society.

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