No abstract

In this work, an alternative utilization of agro-industrial waste coconut endocarp (Cocos nucifera L.) as raw material for the synthesis of magnetic adsorbent aiming the phenol removal is proposed. The synthetized adsorbent, denominated magnetic activated carbon (MAC), was prepared by coprecipitation of cobalt ferrite (CoFe 2 O 4 ) onto activated carbon surface obtained by carbonization of coconut endocarp. Characterization of MAC was carried out by point of zero charge (PZC), Brunauer, Emmett, and Teller (BET) surface area, scanning electron microscopy (SEM), x-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD) analysis, and magnetization curves. Adsorption experiments were performed in batch system to evaluate kinetics and equilibrium of phenol adsorption. Adsorbent regeneration method was proposed to evaluate the reutilization of MAC in successive cycles of adsorption-desorption. Resultsshowed that obtained magnetic compounds present cubic phase structure covered in activated carbon surface. MAC has microporous structure with functional groups like carbonyl and hydroxyl that can behave as adsorption sites.Kinetic studies indicate that adsorption rate increased rapidly around the initial 60 min, reaching equilibrium at 240 min; following pseudo-first-order and pseudo-second-order kinetic models in characterization concentrations of 50 and 100 mg L À1 , only the second-order model fit the kinetic data at 150 mg L À1 , while both models were outside the chi-square interval at 200 and 230 mg L À1 . The adsorption equilibrium is represented by Langmuir isotherm with high adsorption capacity of 116.0 ± 3.61 mg g À1 . The desorption experiments revealed that adsorption capacities of MAC still viable after three adsorption-desorption cycles. It was observed that chemical affinity of small concentrations of methanol with phenol allowed to exert greater desorption capacity to other solvents with permanence of adsorbed phenol of 17.5 mg g À1 .

In this study, we reported data of phase equilibria of the ternary {CO2 (1) + acetone (2) + pluronic F-127 (3)} system using the static synthetic method with a visual cell at temperatures ranging from 303 to 323 K, pressures near to 10 MPa, two concentrations of pluronic F-127 in acetone (0.01 g·cm–3 and 0.02 g·cm–3), and molar fractions varying between 0.3 to 0.9. The thermodynamic modeling using the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EoS) was capable of describing the behavior of the experimental data (liquid–vapor transitions bubble points) satisfactorily.

No presente trabalho, foram estudadas as isotermas de adsorção do CO2 sobre carvão ativado produzido a partir de endocarpo de coco (Cocos nucifera L.) que constitui um resíduo gerado em diversos processos agroindustriais. O carvão sintetizado foi caracterizado por espectroscopia de infravermelho com transformada de Fourier (FTIR), fluorescência de raios X (FRX) e quantificação de grupos ácidos e básicos via método de Boehm. Na obtenção das isotermas de adsorção do CO2 foi utilizada a técnica volumétrica estática em uma coluna de leito fixo de 2 cm de diâmetro interno, 25 cm de altura e volume interno de 138,55 cm3, sob temperatura constante de 24 °C. Os resultados mostraram que a superfície do adsorvente apresentou grupos ácidos, fenólicos, lactonas e básicos. A isoterma de equilíbrio obtida seguiu o comportamento do tipo I da classificação da IUPAC. A capacidade máxima de adsorção de CO2 foi de 64,196 mg.g-1, sob pressão inicial de 3,4 bar e temperatura de 24°C.

In this study, we prepared activated carbon using coconut residue (Cocos nucifera L.) and evaluate the potential use of this activated carbon for capture and storage of carbon dioxide (CO 2). Regeneration tests indicated that the activated carbon has a good regenerative capacity and maypotentially be used in CO 2 adsorption systems. For example, the ability of the activated carbon to capture and then release CO 2 is not significantly affected even after three consecutive adsorption/desorption cycles, regardless of the temperature tested (either 125, 150 or 180°C). Kinetic studies revealed that the time required for total saturation of the activated carbon was 25 min for the pressure range investigated (0.14-0.34 MPa). This ability to retain considerable amounts of CO 2 quickly under low pressures is likely due to the presence of microporous at the surface of this adsorbent, as suggested by reports in the literature and the morphological features of the activated carbon presented here. In addition, equilibrium studies using the Langmuir and Freundlich isotherms showed that the activated carbon has a maximum adsorption capacity of 76.03 mg gG 1 at 15°C. This adsorption capacity decreases with temperature increase, reaching 58.84 mg gG 1 at 35°C. Similar behavior has been observed for other absorbents and is expected for adsorption processes due to the exothermic nature of these processes. In summary, the results indicated that the activated carbon produced with coconut residue has great potential as a CO 2 absorbent.