Effect of channel geometry, degree of activation, relative humidity and temperature on the performance of binderless activated carbon monoliths in the removal of dichloromethane from air

This work addresses the adsorption of dichloromethane (DCM), as a model volatile organic compound (VOC) over activated carbon monoliths (ACM). Several binderless ACM have been prepared at MAST Carbon Ltd. with different channel geometries (square and regular hexagon), cell densities and degrees of activation. The influence of relative humidity (RH) and temperature, as most important atmospheric variables, on DCM adsorption over the ACM have been studied.The influence of the monolith geometric variables onto DCM adsorption has been experimentally proved and explained by the analysis of the mass transfer coefficients. Hexagonal channel monoliths present higher internal and external mass transfer coefficients and lower pressure drops than square ones. The influence of the degree of activation has been studied, both in equilibrium and dynamic vapour phase adsorption experiments. The variation of the degree of activation level from 23% to 40% increased the pore size of this materials leading to higher pore volumes and diffusivities, however DCM enthalpy of adsorption decreased due to confinements effects that are more important for smaller pores.RH and temperature decreased the adsorption capacities at breakthrough and saturation time. As main conclusion, hexagonal channel monoliths with low activation levels present the best properties on DCM adsorption in different atmospheric conditions.

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► Adsorption on activated carbon monoliths (ACM) is a soft technology in VOC abatement.
► The ACM degree of activation leads to an increase in the adsorption capacity for DCM.
► ACM with hexagonal shape perform better than square ones.
► Performance improves increasing the cell density and decreasing the wall thickness.
► The DCM saturation and breakthrough capacities decrease with the relative humidity.