Methyl bromide adsorption on activated carbon to control emissions from commodity fumigations

A process to control emissions of methyl bromide (MB) into the atmosphere f ollowing the fumigation of commodities has been developed. The process cons ists of adsorbing the MB in the vent-stream from a fumigation process onto activated carbon (carbon), Research was undertaken to observe the effects o f (I) temperature, (2) relative humidity (r.h.), (3) the concentration of M B 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 effect 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 significantly for different carbon types. These diff erences were consistent with the type of pore structures of the carbons, wh ich in turn is determined by the raw materials and by the activation proced ures used during the carbon manufacturing process. Temperatures in the carb on column rose in response to the adsorption of MB. By monitoring the tempe ratures, the adsorption zone could be followed throughout the column from t he inlet at the start of an adsorption run to column exhaustion, or breakth rough at the end of the trial. Breakthrough was reached when the MB concent ration in the column exhaust stream reached 500 ppm (2 mg/l) MB. Relative h umidity of the vent-stream was less critical than first 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 increas ed adsorption capacity normally associated with low humidities. Published b y Elsevier Science Ltd.