Cléo T. G. V. M. T. Pires

Organofunctionalized magnesium phyllosilicates as mono- or bifunctitonal entities for industrial dyes removal

Magnesium phyllosilicates with organic groups anchored onto the inorganic polymeric backbones as mono- or bifunctional entities were investigated for dye removal from aqueous solution. The synthetic methodology consisted in obtaining organofunctionalized nanostructured materials from silylating agents of general formula R1–Si(OCH3)3, in which R1-trimethoxysilane includes chains containing the functional groups: 3-aminopropyl, octadecyldimethyl(silylpropyl)ammonium, 3-mercaptopropyl, 3-ethylenediamine and 3-diethylenetriamine. The sol–gel process leads to lamellar structures similar to those of natural silicate with basal distances, in good agreement with the R1 contained in the precursor agent. The pendant electrophile attached on the new phyllosilicates interacts with the negative charge of dyes used in the textile industry, such as Reactive Yellow GR, Reactive Red RB and Reactive Blue RN. The sorption studies showed that the phyllosilicate containing octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride agent, P-OCT, presented the highest sorption capacities of 1343, 1286 and 344 mg g−1 for the dyes Yellow GR, Blue RN and Red RB, respectively, which are better than for other sorbing materials. Real samples from textile effluents assayed demonstrated that the sorption did not need to adjust the initial pH, with surface saturation after 3 h and the minimum mass necessary was 2.5 g dm−3 of P-OCT for the best efficiency. This is thus a very promising material for textile effluent treatment, with good structural disposition of the pendant groups.

A Useful Synthetic Route to Yield Silver-Nanoparticles on Phyllosilicates and Morphologic Structural Investigations

Organofunctionalized phyllosilicates containing both amino and mercapto groups were synthesized and used as support for silver nanoparticles in situ deposition. Depending on silver concentration in relation to phyllosilicate different amount of nanoparticles size and distributions were obtained, even with smallest silver used causes strong exfoliation of the phylosilicate lamella. Also such condition favors nanoparticles formation with homogeneous distribution with smaller diameters and narrower particle particles size distributions. With highest silver amounts preferential external phyllosilicate surface crystallization is obtained, as given by particle diameters up to 30 nm. Scanning and transmission electron microscopies were successfully employed to characterize morphological and structural features for these synthesized materials, enabling atomic visualization for the silver nanoparticles. These new phyllosilicates containing silver nanoparticles are extensively employed to design inorganic light emission diodes and also in applying in biological fields.

1H NMR spectroscopy study of water adsorbed on the surface of layered ilerite

The hydrated layered alkaline silicate ilerite synthesized by a hydrothermal methodology was characterized by various techniques that confirmed a good structural quality of the resulted material. In an attempting to investigate the characteristics of water boundary layers in this hydrated powder sorbent, 1H NMR spectroscopy method was performed to measure the temperature dependence of the observed proton signal intensities in water sorbed, from 200.15 to 298.15 K. Gibbs energy of water molecules at the sorbent water interface decreased due to the sorption interactions, causing the water dosed to the sorbent surface freezes at T < 273.15 K. Due to a disturbing action of the sorbent surface and confined space, water occurs in the quasi-liquid state. As a result, it is observed in the 1H NMR spectra narrow signal relatively, but increase in peak broadening with the decrease of temperature. The presence of two types of hydrogen bonding was observed with the presence of signals around 3.9 and 16 ppm. The water...