Methyl Bromide Adsorption on Activated Carbon to Control Emissions from Commodity Fumigations

Abstract A process to control emissions of methyl bromide (MB) into the atmosphere following the fumigation of commodities has been developed. The process consists of adsorbing the MB in the vent-stream from a fumigation process onto activated carbon (carbon). Research was undertaken to observe the eects of (1) temperature, (2) relative humidity (r.h.), (3) the concentration of MB in the vent-stream, and (4) carbon type on the amount of MB that could be adsorbed (loaded) on the activated carbon. Temperature had the most eect on the loading, followed by r.h., for a given type of carbon. The loading decreased as temperature and r.h. increased. For a given temperature and r.h., the loading varied signi®cantly for dierent carbon types. These dierences were consistent with the type of pore structures of the carbons, which in turn is determined by the raw materials and by the activation procedures used during the carbon manufacturing process. Temperatures in the carbon column rose in response to the adsorption of MB. By monitoring the temperatures, the adsorption zone could be followed throughout the column from the inlet at the start of an adsorption run to column exhaustion, or breakthrough at the end of the trial. Breakthrough was reached when the MB concentration in the column exhaust stream reached 500 ppm (2 mg/l) MB. Relative humidity of the vent-stream was less critical than ®rst anticipated because of the heating of the column. The temperature increase due to the heat of adsorption lowered the r.h. at the adsorption zone which led to the increased adsorption capacity normally associated with low humidities. Published by Elsevier Science Ltd