RESUMEN
Physical adsorption on activated carbons has shown to be a very attractive methodology for CO2 separation from flue gas streams and biogas. In this context, the goal of this work was to prepare granular activated carbons intended for CO2 adsorption from an abundant and low-cost biomass residue (coconut shell) by using practical and cost-effective procedures. By the first time, parameters involved in chemical activation with dehydrating agents (H3PO4 or ZnCl2) and/or physical activation with CO2 were systematically screened in depth in order to obtain materials with improved performance for CO2 adsorption on a volume basis. Compared with the commonly used mass basis, the data expressed on a volume basis are very important for industrial applications because they permit to estimate the efficiency of a fixed bed adsorption column. The work permitted to prepare granular activated carbons with a blend of relatively high gravimetric CO2 uptake and bulk density, so that high volumetric CO2 uptakes were attained. The highest values were 2.67 and 1.17 mmol/cm3 for CO2 pressures of 1.0 and 0.15 bar, respectively. It is remarkable that the obtained results were similar to those reported by other authors for carbons chemically activated with KOH, the activation methodology that has been widely claimed as the one that produce ACs with the best performances for CO2 adsorption, but which involves severe restrictions. Therefore, the present work can be considered a very important step in paving the way toward making CO2 adsorption an each time more interesting technology to reduce the emissions of anthropogenic greenhouse gases.
RESUMEN
AIM: Sol-gel is a suitable and advantageous method to synthesize mixed oxide nanomaterials with unique physicochemical and biological properties. MATERIALS & METHODS: In this work, TiO2-SiO2 nanopowders cogeled with platinum acetylacetonate were developed and studied in the perspective of nanomedicine. The physicochemical properties of the Pt/TiO2-SiO2 nanopowders, named NanoRa2-Pt, were evaluated in detail by means of complementary spectroscopic and microscopic tools. The nanopowder's biocatalytic efficiency in wound healing was evaluated in a Type I diabetes animal model. RESULTS: These are TiO2-SiO2 submicron mesoporous particles with variable size and shape containing ultra-small platinum nanoparticles with catalytic properties. CONCLUSION: The use of NanoRa2-Pt catalyzes the natural healing processes with a faster remodeling stage. These sols, which we call nanobiocatalysts, belong to an emerging and very promising research field known as catalytic nanomedicine.
Asunto(s)
Nanopartículas/química , Platino (Metal)/química , Dióxido de Silicio/química , Titanio/química , Cicatrización de Heridas/efectos de los fármacos , Animales , Catálisis , Complicaciones de la Diabetes/tratamiento farmacológico , Complicaciones de la Diabetes/fisiopatología , Diabetes Mellitus Tipo 1/complicaciones , Diabetes Mellitus Tipo 1/tratamiento farmacológico , Humanos , Masculino , Nanopartículas del Metal/química , Nanomedicina , Porosidad , Ratas , Ratas Wistar , Propiedades de SuperficieRESUMEN
KOH activation of a mesophase pitch produces very efficient carbons for the removal of sulfide in aqueous solution, increasing the sulfur oxidation rate with the degree of activation of the carbon. These carbons are characterized by their graphitic structures, with domains of sizes of around 20 nm, and a moderate concentration of surface oxygen groups (0.2-0.5 mmol·g-1) dominating the basic groups. Because the activation leads first to a strong development of the micropores and later to a development of the mesopores, the surface area values are always high, reaching values of as high as 3250 m2·g-1 in the most activated carbon, with a volume of mesopores of as high as 44% of the total pore volume. In the presence of this carbon, the sulfide oxidation rate is 100 times higher than that found for a commercial activated carbon, the results indicating that the porosity of the carbon, especially mesoporosity, plays a role more important than the structure or the chemical nature of the carbon in the kinetics of sulfide oxidation to different polysulfides.
RESUMEN
The catalytic adsorption of NO on activated carbon materials provides an appropriated alternative for the control of low-concentration emissions of this air pollutant. The surface complexes formed upon NO adsorption at 30 degrees C were studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The effects of the addition of O2 and the presence of copper as a catalyst were studied. Copper assisted the oxygen transfer to the carbon matrix. For the Cu-impregnated carbon sample, the presence of O2 favored NO adsorption by increasing the breakthrough time, the adsorption capacity, and the formation of nitrogen and oxygen complexes of higher thermal stabilities, which mainly desorbed as NO and CO2.