Cu n Clusters (n = 13, 43, and 55) as Possible Degradant Agents of mSF6 Molecules (m = 1, 2): A DFT Study.

In order to obtain the structural and electronic properties of pristine copper clusters and Cu13-SF6, Cu43-SF6, Cu55-SF6, Cu13-2SF6, Cu43-2SF6, and Cu55-2SF6 systems, DFT calculations were carried out. For Cu13-mSF6, its surface suffers a drastic deformation, and Cu43-mSF6 at its outer surface reveals strong interaction for the first chemical molecule; when the second molecule is interacting, these outer surfaces are not severely affected. These two cases degraded fully the first SF6 molecule; however the second molecule is bonded to the latter systems and for Cu55-mSF6 (m = 1 and 2) a structural transformation from SF6 →SF4 appears as well as inner and outer shells that display slight deformations. The electronic gaps do not exhibit drastic changes after adsorption of mSF6 molecules, and the magnetic moment remains without alterations. The whole system shows thermal and vibrational stability. In addition, for Cu13-mSF6 the values of the optical gap and intensity of the optical exhibit changes with respect to the pristine case (Cu13), and the rest of the systems do not exhibit major oscillations. These icosahedral copper clusters emerge as a good option to degrade mSF6 molecules.

Adsorption of textile dyes using an activated carbon and crosslinked polyvinyl phosphonic acid composite.

Activated carbon is one of the most studied materials for the adsorption of textile dyes. The adsorptive properties of this material are a result of its high specific surface area and some of the functional groups acquired during the chemical activation. This work reports the preparation of a composite material using CarZN400 activated carbon and polyelectrolyte poly(VPA-co-TEGDMA). The adsorptive properties of the material obtained are a result of the combination of the high specific surface area of the carbon and the ionic exchange capability of the polyelectrolyte. The covering of the surface of activated carbon with poly(VPA-co-TEGDMA) allowed to obtain a composite material (CarZN400C) with greater adsorption capacity for cationic dyes compared to the carbon. The adsorption isotherms of the dyes fit Langmuir's model, and the adsorptive capacities for cationic dyes for CarZN400C ranged between 222 and 416 mg/g. The kinetic study showed that the adsorption of basic and acid dyes fit the pseudo-second order kinetic model. CarZN400C also exhibited the ability to adsorb textile dyes present in wastewater. It was observed that, when making a previous treatment of the wastewater using coagulation-flocculation followed by adsorption using CarZN400C, it was possible to obtain removal percentages of color close to 100%. The wastewaters treated by coagulation-flocculation and adsorption improved their quality by decreasing the value for COD.

Elimination of textile dyes using activated carbons prepared from vegetable residues and their characterization.

In this study, three mesoporous activated carbons prepared from vegetable residues were used to remove acid, basic, and direct dyes from aqueous solutions, and reactive and vat dyes from textile wastewater. Granular carbons obtained by chemical activation at 673 K with phosphoric acid from prickly pear peels (CarTunaQ), broccoli stems (CarBrocQ), and white sapote seeds (CarZapQ) were highly efficient for the removal of dyes. Adsorption equilibrium studies were carried out in batch systems and treated with Langmuir and Freundlich isotherms. The maximum adsorption capacities calculated from the Langmuir isotherms ranged between 131.6 and 312.5 mg/g for acid dyes, and between 277.8 and 500.0 mg/g for basic dyes at 303 K. Our objective in this paper was to show that vegetable wastes can serve as precursors for activated carbons that can be used for the adsorption of dyes. Specifically CarBrocQ was the best carbon produced for the removal of textile dyes. The color removal of dyes present in textile wastewaters was compared with that of a commercial powdered carbon, and it was found that the carbons produced using waste material reached similar efficiency levels. Carbon samples were characterized by bulk density, point of zero charge, thermogravimetric analysis, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, methylene blue adsorption isotherms at 303 K, and nitrogen adsorption isotherms at 77 K (SBET). The results show that the activated carbons possess a large specific surface area (1025-1177 m(2)/g) and high total pore volume (1.06-2.16 cm(3)/g) with average pore size diameters between 4.1 and 8.4 nm. Desorption and regeneration tests were made to test the viability of reusing the activated carbons.

Determination of textile dyes by means of non-aqueous capillary electrophoresis with electrochemical detection.

Eight textile dye compounds including five cationic dyes, namely, basic blue 41, basic blue 9, basic green 4, basic violet 16 and basic violet 3, and three anionic dyes, acid green 25, acid red 1 and acid blue 324, were separated and detected by non-aqueous capillary electrophoresis (NACE) with electrochemical detection. Simultaneous separations of acid and basic dyes were performed using an acetonitrile-based buffer. Particular attention was paid to the determination of basic textile dyes. The optimized electrophoresis buffer for the separation of basic dyes was a solvent mixture of acetonitrile/methanol (75:25, v/v) containing 1 M acetic acid and 10 mM sodium acetate. The limits of detection for the basic dyes were in the range of 0.1-0.7 microg mL(-1). An appropriate solid-phase extraction procedure was developed for the pre-treatment of aqueous samples with different matrices. This analytical approach was successfully applied to various water samples including river and lake water which were spiked with textile dyes.