Produção de estruturas carbonáceas sustentáveis e sua aplicação na remoção de compostos orgânicos voláteis (COVs)

Abstract

Activated carbons were prepared from banana pseudostem and used to capture 5 different volatile organic compounds (VOCs), which are dichloromethane, chloroform, ethyl acetate, hexane and cyclohexane. The biomass was first dried in an oven and passed through a process of hydrothermal pyrolysis followed by a dry pyrolysis and the activating agents used were KOH or ZnCl2. Activated carbons showed high surface areas (701-1312m²/g), and different pore size distributions. VOC capture studies were performed in thermal analyzer and capacity up to 933mg/g for dichloromethane, 775mg/g for chloroform, 480mg/g for ethyl acetate, 414mg/g for hexane and 376mg/g for cyclohexane were reached, and these values are higher than those presented by some studies in the literature. Higher adsorption capacities were related to the amount of available micropores, and this capture capacity was enhanced by the amount of small mesopores. As the highest adsorbed amounts were obtained for the material activated with ZnCl2 in greater proportions and for the dichloromethane molecule, further studies were carried out with this adsorbent and this adsorbate. The variation of the adsorption isotherm showed that it is an exothermic process and that it is governed by physisorption, and this hypothesis was confirmed with the pseudo first order kinetic model, where this model was the one that most adjusted to the studies . The study in different atmospheres showed that there is a coadsorption phenomenon and the relative humidity studies showed that the capture capacity decreases slightly at equilibrium. The cycle test proved that the adsorbent can be used in up to 10 adsorption/desorption cycles without significantly losing its efficiency.