Activated carbons were prepared from a lignocellulosic material, African palm shells (Elaeis guineensis), by chemical impregnation of the precursor with solutions of 1–7% w/v Cu­(NO3)2 at five different concentrations. These were carbonized in a carbon dioxide atmosphere at 1073 K to obtain different carbons. Their textural properties were characterized by nitrogen and carbon dioxide adsorption isotherms in order to evaluate the pore-size distribution. The immersion enthalpies of the activated carbons in benzene, dichloromethane, and water were determined. The CO2 adsorption capacities of the materials at 273 K under low-pressure conditions were also determined. Chemical characterization was performed by mass spectrometry, Fourier transform infrared spectroscopy, and temperature-programmed reduction. With this method of preparation under the concentrations described, activated micro–mesoporous carbons were obtained, with the formation of highly mesoporous solids that favored the process of diffusion of molecules of CO2 into the material. Here, we show that activated carbons were obtained with different textural characteristics: surface Brunauer–Emmett–Teller areas varied between 473 and 1361 m2 g–1 and micropore volume between 0.18 and 0.51 cm3 g–1. The activated carbon with the highest values of textural parameters was ACCu5-1073. Micro–mesoporous solids were obtained with the methodology used. This is important as it may help the entry of CO2 molecules into the pores. The adsorption of CO2 in the materials prepared presented values between 103 and 217 mg CO2 g–1; the values of volume of narrow microporosity obtained were between 0.16 and 0.45 cm3 g–1. The solid with the greatest capacity for adsorption of CO2 and volume of narrow microporosity was ACCu3-1073. The use of these solids is of importance for future practical and industrial applications. The adsorption kinetic of CO2 in the activated carbons prepared with metallic salt of copper is in good accordance with the intraparticle diffusion model, for which diffusion is the rate-limiting step. The adsorption of CO2 in the prepared activated carbons is favorable from the energy and kinetic point of view, as these accompanied by the presence of wide micro–mesoporosity favor the entry of CO2 into the micropores.

<p>Se obtuvieron carbones activados mediante activación química de cuesco de palma africana con soluciones de cloruro de magnesio y cloruro de calcio a diferentes concentraciones. Los materiales preparados se caracterizaron textural y químicamente. Los resultados obtenidos muestran que los carbones activados con los mayores valores de área superficial y volumen de poro se obtienen cuando se emplean soluciones con las menores concentraciones del agente activante. Los carbones activados obtenidos presentan áreas superficiales y volúmenes de poro con valores entre 10 y 501 g y 0,01 y 0,29 cm/g respectivamente. Los valores de las entalpías de inmersión de los sólidos en agua se encuentran entre -14,3 y -32,8 J/gy en benceno entre -13,9 y -38,6 J/g. La acidez y la basicidad total de los carbones activados presentan valores entre 23 y 262 µmol/g y 123 y 1724 µmol/g respectivamente. También se determinó el pH en el punto de carga cero, con valores entre 4,08 y 9,92 para el conjunto de los carbones activados. Los resultados muestran que la activación con las sales MgCl y CaCl producen carbones activados con poros en el rango de los mesoporos que facilitan la entrada del adsorbato al interior del material.</p>

Granular-type activated carbons were prepared from African palm shells (Elaeis guineensis) by chemical activation with aqueous solutions of MgCl 2 and CaCl 2 at concentrations of 3, 5 and 7 % w/v, at temperatures between 773 and 1073 K. The textural parameters were obtained from N 2 adsorption isotherms of the prepared activated carbons. The textural parameters included the surface area and pore volume, with values between 10 and 501 m 2 g -1 and 0.01 and 0.29 cm 3 g -1 , respectively. Enthalpic characterisation of the activated carbons was performed through the immersion calorimetry technique in three different solvents: benzene, cyclohexane and water. The enthalpies of immersion values of the solids in water were between -7.4 and -42.7 J g -1 ; for the immersion in benzene, the values were between -13.9 and -38.6 J g -1 and were between -6.4 and -24.2 J g -1 for the immersion in cyclohexane. The results show that activation with MgCl 2 and CaCl 2 salts produces activated carbons with differences in their characteristics of energy and affinity for the calorimetric liquids that are related to the surface properties.Keywords Activated carbon Á Chemical activation Á CaCl 2 solutions Á MgCl 2 solutions Á N 2 adsorption Á pH at point of zero charge Á Enthalpy of immersion Á Hydrophobic factor

This article has been retracted due to honest error by the author. For further information, please see https://doi.org/10.1515/ijcre-2017-9198. Activated carbons are obtained by chemical activation of African Palm shells (Elaeis guineensis) with different impregnating agents, i. e. magnesium chloride (MgCl2) and calcium chloride (CaCl2) aqueous solutions at different concentrations (3, 5 and 7 % w/v) and temperatures (between 773 and 1073 K), in order to assess their influence on the development of the porosity. The activated carbons prepared are characterized in terms of both textural and chemical properties. The activated carbons have a surface area and a pore volume ranging between 19–501 m2.g−1 and 0.03–0.29 cm3.g−1, respectively. Based on the obtained results, the samples with higher surface area and pore volume (i. e. those impregnated with MgCl2 and CaCl2 solutions and thermally treated at 1073 K) are selected to evaluate the adsorption capacity and affinity for CO2. CO2 adsorption capacity varies between 1.78 and 2.95 mmolCO2.g−1 at 273 K and low pressure, and the activated carbon impregnated with the solution of MgCl2 3 % and activated at 1073 K (i. e. ACMg3-1073) showed the best performances. Finally, the kinetic results show that adsorption rate for sample ACMg3-1073 is enhanced by its micro-mesoporous nature, being the access routes to the micropores larger.

En la presente investigación se prepararon sólidos porosos tipo carbón activado (CA) a partir de la activación química del cuesco de palma africana procedente de los cultivos de la región de la Guajira, Colombia, con soluciones de Fe(NO3)3 y Cu(NO3)2 con cambio en la concentración a dos diferentes temperaturas: 973 y 1073 K. Los sólidos adsorbentes preparados se caracterizaron para determinar sus propiedades fisicoquímicas y capacidades de adsorción de CO2. Los CA obtenidos presentan micro-mesoporosidad con áreas superficiales entre 5 y 1300 m2g-1. Los valores con respecto al contenido de carbono fijo se encuentran entre 47,1 y 78,4%; los resultados evidencian que el proceso de activación tiene efectos sobre los parámetros texturales, composición elemental y proximal de los sólidos obtenidos. También se realizó la caracterización morfológica de la superficie de los materiales con SEM evidenciando la formación de mayor rugosidad en las muestras activadas a 1073 K, específicamente, los carbones activados con el nitrato cúprico; además, mediante EDX se cuantificó la presencia de algunos elementos. Los valores obtenidos de la adsorción de CO2 a bajas presiones se encuentran entre 80 y 250 mg·g-1, evidenciándose una mayor afinidad hacia los sólidos adsorbentes (MCu3 y MFe5).

No abstract

No abstract

Retraction of https://doi.org/10.1515/ijcre-2017-0198.