No abstract

La semilla de aguaje (fruto típico de la selva amazónica) fue empleada como un material precursor para la preparación de carbón activado usando ácido fosfórico como agente activante en dos concentraciones diferentes: 0,75 y 1,0 g /g . Las propiedades H3PO4 Precursor fisicoquímicas se estudiaron mediante mediciones de adsorción de nitrógeno, titulación Boehm, microscopía electrónica de barrido y espectroscopía de rayos X por energía dispersiva. Los carbones activados se utilizaron en la adsorción de tres metales pesados: plomo, cadmio y cromo. La máxima capacidad de adsorción se logró utilizando el carbón activado AG0,75_600 con soluciones con un pH mayor a 4; los valores obtenidos estaban en el -1 -1 -1 siguiente orden: plomo (74,8 mg g ) , cadmio (26,5 mg g ), cromo (18,8 mg g ). Los factores más importantes que influyen en el proceso de adsorción fueron el pH de la solución, la estructura porosa y la acidez superficial del carbón activado.

View references (22) Water-resistant MOF-235 was used to adsorb N,N-dimethylamine (DMA) from aqueous solutions. It was synthesized from terephthalic acid and FeCl3.6H2O under air-free conditions and characterized by its crystalline structure, functional groups and temperature resistance. The kinetic data results were best adjusted to the pseudo-second order model (R 2 >0.963). The best-fit isotherm, Langmuir model, suggested the adsorption of DMA is localized on homogenously distributed active sites on the surface. This fit was confirmed by the value of β = 1 on the Redlich-Peterson model. Our study suggests that the manipulation of novel materials such as MOF-235 promises new avenues for water treatment solutions. Schematic structure of MOF-235 and its application as adsorbent.

Activated carbons (ACs) were prepared from aguaje seeds at different impregnation ratios of (Formula presented.)/precursor equivalent to 0.5, 0.75, 1.0 and 1.5, for the adsorption of N,N-dimethylamine (DMA). The samples were characterized by (Formula presented.)-sorption ((Formula presented.)), X-ray diffraction, infrared spectroscopy (FTIR), Boehm titration, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The samples were successfully activated to obtain highly microporous surface (>95 %) with high total BET surface area ((Formula presented.)695 (Formula presented.)). Common acid functional groups were determined by the Boehm titration and FTIR. The kinetic data revealed that the results were better adjusted to pseudo-second order and Elovich models. To predict the adsorption process, different isotherm models were tested. The best t isotherm model for AC-0.5 and AC-0.75 samples was the Temkin isotherm model. Meanwhile, the Langmuir isotherm was the best t model for AC-1.0 and AC-1.5 samples. Moreover, it was found that the adsorption of DMA was highly in uenced by the surface acidity and the microporosity of the carbons.

Activated carbon was prepared from the seeds of aguaje palm ( Mauritia flexuosa L.f.) by a chemical activation with phosphoric acid. This activated carbon was used for adsorbing metal ions: Pb(II), Cd(II), and Cr(III). To understand the mechanism of adsorption of these heavy metals (Cr, Cd, and Pb), the activated carbon surface was oxidized with nitric acid (1 M) increasing the oxygenated surface groups showing an increasing in their adsorption capacities of these metals. The oxidized activated carbon slightly increased the maximum adsorption capacity to 5–7%. The order of adsorption for unoxidized and oxidized activated carbons was Pb> Cd> Cr. This experimental information was corroborated by molecular modeling program Hyperchem 8 based adsorption mainly on two factors: the electron density and orbitals—highest occupied molecular orbital and lowest unoccupied molecular orbital.Activated carbons were characterized by adsorption/desorption of N2, obtaining an increase of microporous surface area for oxidized activated carbon. An increase of surface acidity and a reduction of isoelectric points were observed in oxidized activated carbon. According to these results, the adsorption of metal ions is favored in contact with an oxidized activated carbon, which has more amount of phenolic and carboxylic functional groups. Similarly, decreasing the isoelectric point indicates that the surface has a higher negative charge. The surface information was corroborated by Hyperchem, which indicates that the surface of the oxidized activated carbon has a higher electron density, indicating a larger amount of electrons on its surface, which means the surface of oxidized activated carbon charges negatively and thereby attracts metal ions.