Characterization of MgCl2/AC composite adsorbent and its water vapor adsorption for solar drying system application.

Abstract In order to realize dehumidification and heat recovery from solar drying system, a fresh walnut-shell activated carbon (AC0) was prepared by KOH chemical activation method and used as a novel host matrix for hygroscopic salt MgCl 2 impregnation. The effects of MgCl 2 loading amounts and cerium (Ce) addition on water vapor adsorption performance of the composite adsorbents were investigated. N 2 adsorption-desorption isotherm and scanning electron microscope were employed to characterize pore development and morphology of the composite adsorbents. Finally, regenerabilities and stabilities of AC0, AC40 (theoretical MgCl 2 loading amount 40 wt%), and AC404 (theoretical MgCl 2 loading amount 40 wt% and theoretical Ce addition amount 4 wt%) were studied. The results show that water vapor adsorption amount of the composite adsorbents decreases slightly and then increases significantly with the increase of the MgCl 2 loading amount. Under the 70% relative humidity and the adsorption temperature of 298 K, water vapor adsorption amounts of AC0, AC40, and AC404 are 0.6022 g/g, 0.9410 g/g and 1.0502 g/g, respectively. AC0 does well in excellent reversibility of water vapor adsorption. Ce addition slightly promotes uniform distribution of MgCl 2 within the composite adsorbent, prevents the conversion from MgCl 2 ·6H 2 O to Mg 2 CO 3 Cl(OH)·3H 2 O, and improves adsorption-regeneration performance. The present study confirms that the composite adsorbent would be one of the potential candidates for dehumidification and heat recovery in solar drying system. Highlights • A walnut-shell activated carbon is prepared and used for MgCl 2 modification. • The effect of MgCl 2 loading amount on water vapor adsorption were studied. • The maximum of water vapor adsorption amount onto AC404 was 1.0502 g/g. • AC0 possessed an excellent reversibility of water vapor adsorption. • Ce addition improved the adsorption-regeneration performance of AC404. [ABSTRACT FROM AUTHOR]