Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15.

Mesostructured silica SBA-15 and amino-functionalized silica SBA-15-NH2 were synthesized, and then, characterization, adsorption capacity, and immersion enthalpies in caffeine and glyphosate on SBA-15 and SBA-15-NH2 were evaluated. The enthalpy parameter was determined using a local construction Tian-type heat conduction calorimeter. Calorimetric studies in caffeine solutions exhibit negative enthalpy values; exothermic process characteristics for SBA-15 were between -13.90 and -194.06 J g-1 and those for SBA-15-NH2 were between -7.22 and -60.34 J g-1, and the adsorption capacity of caffeine was better in SBA-15 than that in SBA-15-NH2. In contrast, the enthalpies of immersion in glyphosate solutions were -5.06 to -56.2 J g-1 and the immersion of SBA-15-NH2 in each solution generated enthalpy values of -9.06 to -41.2 J g-1, but the adsorption capacity of glyphosate was better in the amino-functionalized SBA-15. The results show that functionalization of SBA-15 produced differences in physicochemical characteristics of solids, since energy and affinity for the calorimetric liquids are related to the surface properties of solids as well as the chemical nature of the target molecule, immersion enthalpy, was different.

Simple and Competitive Adsorption Study of Nickel(II) and Chromium(III) on the Surface of the Brown Algae Durvillaea antarctica Biomass.

In this work Ni(II) and Cr(III) adsorption on Durvillaea antarctica surface were studied, optimal condition of pH, adsorption time is achieved at pH 5.0, with contact times of 240 and 420 minutes for a maximum adsorption capacity of 32.85 and 102.72 mg g-1 for Ni(II) and Cr(III), respectively. The changes in the vibration intensity of the functional groups detected in the starting material by Fourier transform infrared spectroscopy and the opening of the cavities after the biosorption process detected by scanning electron microscopy images suggested the interaction of the metal ions with the surface and the changes in the chemical behavior of the solid. The heavy metal adsorption equilibrium data fitted well to the Sips model. The effect of competitive ions on adsorption equilibrium was also evaluated, and the results showed that the two metals compete for the same active sites of the biosorbent; the increase of the Ni(II) initial concentration increases its adsorption capacity but decreases the adsorption capacity of Cr(III).

Data for the synthesis of pyrogallol-formaldehyde aerogels using two acid catalysts oxalic acid y hydrochloric acid.

Aerogels are extremely porous materials with large pore volumes and low bulk densities. Their unique structure imparts extraordinary properties and wide applications. The synthesis of pyrogallol-formaldehyde xerogels has been reported using HClO4 as a catalyst, but according to the literature review the synthesis of aerogels of these materials has not been documented. In the present work, the data for the synthesis of aerogels pyrogallol-formaldehyde are presented using oxalic acid and hydrochloric acid as catalysts. Also includes the data of the characterization of these materials by Infrared spectroscopy, thermogravimetric analysis Tg-DTG, Physisorption of N2, Raman Spectroscopy, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It was determined that the use of these precursors of the synthesis of aerogels in acid medium, leads to the obtaining of microporous solids with a high value of the surface area, the material with the highest value of this parameter has been CAePF OA550 at have a BET area value of 1066 m2 g-1.

Adsorption of Cd (II) on Modified Granular Activated Carbons: Isotherm and Column Study.

In this work, equilibrium and dynamic adsorption tests of cadmium Cd (II) on activated carbons derived from different oxidation treatments (with either HNO3, H2O2, or NaOCl, corresponding to GACoxN, GACoxP, and GACoxCl samples) are presented. The oxidation treatments determined an increase in the surface functional groups (mainly the acidic ones) and a decrease in the pHPZC (except for the GACoxCl sample). A slight alteration of the textural parameters was also observed, which was more significant for the GACoxCl sample, in terms of a decrease of both Brunauer-Emmett-Teller (BET) surface area and micropore volume. Adsorption isotherms were determined for all the adsorbents and a significant increase in the adsorption performances of the oxidized samples with respect to the parent material was observed. The performances ranking was GACoxCl > GACoxP > GACoxN > GAC, likely due to the chemical surface properties of the adsorbents. Dynamic tests in a fixed bed column were carried out in terms of breakthrough curves at constant Cd inlet concentration and flow rate. GACoxCl and GACoxN showed a significantly higher value of the breakpoint time, likely due to the higher adsorption capacity. Finally, the dynamic tests were analyzed in light of a kinetic model. In the adopted experimental conditions, the results showed that mass transfer is controlled by internal pore diffusion, in which surface diffusion plays a major role.

Oxidación de lassuperficie de carbón activado mdiante hno3 y h2o2: efecto sobrre la remoción de níquel (ii) en solución acuosa / Activated carbon surface oxidatio by hno3 and h2o2: effect on the removal of nicckel (ii) from aqueous solution / Oxdação da superrfície de carvão aivado por meio de hno3 e h2o2: efeito na remoção de níquel (ii) em solução aquosa

Este trabajo analiza el efecto de la modificación de la química superficial de un carbón activado granular, CAG, por oxidación con ácido nítrico, CAG-N, y peróxido de hidrogeno, CAG-P en la adsorción de iones níquel desde solución acuosa. Las muestras obtenidas se caracterizaron a través de diferentes técnicas; la química superficial se evaluó por determinaciones de acidez y basicidad total, punto de carga cero y espectroscopia IR, que muestran el efecto del agente oxidante. Los parámetros texturales, como área superficial BET y volúmenes de poro, se evaluaron mediante adsorción de gases. Los valores de área superficial BET de los sólidos se encuentran entre 816 y 876 m²g-1, adicionalmente se determinaron entalpías de inmersión de los carbones activados en agua y benceno. Finalmente, los resultados experimentales de la adsorción desde solución se ajustaron a los modelos de Langmuir, Freundlich, Redlich-Peterson y Toth, y se encontró el mejor ajuste para este último. Los valores de la capacidad de adsorción determinadas por el modelo de Langmuir están entre 29,68 y 50,97 mg g-1, lo que indica que la capacidad de adsorción depende, en gran medida, de la química superficial del sólido.

In this work is studied the effect in the surface chemistry modification of a granular activated carbon, CAG, by oxidation with nitric acid, CAG-N, and hydrogen peroxide, CAG-P, in the nickel ions adsorption from aqueous solution. The samples were characterized by different techniques, surface chemistry was evaluated by acidity and basicity total determinations, point of zero charge and IR spectroscopy that show the effect of oxidant agent. The textural parameters such as BET surface area and pore volumes were evaluated by gas adsorption. The BET surface area values of the solids are between 816 and 876 m²g-1; additionally were determined immersion enthalpies in water and benzene. Finally, the experimental results of the adsorption from solution were adjusted to the Langmuir's, Freundlich's, Redlich-Peterson's and Toth's models, and were found the best adjustment for the latter. The capacity adsorption determined by Langmuir's model is between 29.68 50.97 mg g-1, which indicates that the adsorption capacity depends to a great extent on the solid surface chemistry.

Neste trabalho se estudou o efeito na da modificação da química superficial de um carvão ativado granular, CAG, por oxidação com ácido nítrico, CAG-N, e peróxido de hidrogênio, CAG-P na adsorção de íons níquel desde solução aquosa. As mostras obtidas foram caracterizadas por diferentes técnicas; a química superficial foi avaliada por determinações de acidez e basicidade total, ponto de ônuszero e espectroscopia IR, que mostram o efeito do agente oxidante. Os parâmetrostexturais, como área superficial BET e volumes de poro se avaliaram mediante adsorção de gases. Os valores de área superficial BET dos sólidos se encontram entre 816 e 876 m²g-1, adicionalmente se determinaram entalpias de imersão dos carvõesativados em água e benzeno. Finalmente, os resultados experimentais da adsorção desde soluçãoforam ajustados aos modelos de Langmuir, Freundlich, Redlich-Peterson e Toth, e se encontrou o melhor ajuste para esse último. Os valores da capacidade de adsorção determinados pelo modelo de Langmuir estão entre 29,68 e 50,97 mg g-1, o que indica que a capacidade de adsorção depende em grande parte da química superficial do sólido.