Observations and Comments on the Displacement of Pre-Adsorbed Water from BPL Activated Carbon by Chloropicrin Vapour

Abstract

The breakthrough curves of chloropicrin vapour through beds of BPL activated carbon pre-equilibrated at different relative humidities (RH) have been measured. The associated water displacement curves and effluent temperature profiles are also presented. At first, as the experimental RH increases, the slope of the breakthrough curves gradually decreases. However, at high RH (i.e. 80%) the curve becomes distinctly biphasic. It is proposed that the initial steep part of the curve is the result of a build-up of water in the macro (transport) pore structure of the carbon which restricts access of chloropicrin to the micropores. The accumulation of water in the transport pores is a consequence of both the high carbon water content at RH 80% and the limitation on the amount of water that can be carried away in the air- stream (which rapidly reaches saturation). The shape of the water displacement curves is also influenced by re-adsorption of displaced water further along the filter bed. In most experiments there is a significant depression in the temperature of the effluent airstream. At RH 80% the overall process is notably endothermic.