Abstract: Activated charcoal, or ASC whetlerite charcoal for use in providing protection against chemical warfare agents, contains chromium VI, which is a known carcinogen, as well as other metal impregnants. Thus disposal of the charcoal can present problems. The charcoal is usually impregnated with the chromium and other active metals by placing the charcoal in a solution of the metals, and oven drying the charcoal so that crystals are deposited thereon. It has been found that if the charcoal is freeze-dried the quantity of the metals such as chromium VI can be reduced by as much as 50% without compromising the performance of the charcoal.

Abstract: Activated carbon is used on gas-mask canisters for filtering air to remove toxic vapors. For military use, the charcoal is impregnated with inorganic salts or organic compounds for improving the chemical activity of the charcoal with respect to toxic vapors having low boiling points and small molecular sizes, e.g. cyanogen chloride. One such compound, namely triethylenediamine (TEDA) has been added to charcoal by sublimation at atmospheric pressure. A more effective method of impregnating charcoal with TEDA utilizes reduced pressure 0.13 to 13 Pa, preferably 1.3 Pa as a driving force to facilitate vaporization of the TEDA by sublimation. The activated carbon to be impregnated is dried at 110.degree. C. to 160.degree. C. for three hours and transferred to a vacuum desiccator. The required amount of the amine, namely 1.57 to 12.57%, preferably 4.7% is placed in the container on top of the activated carbon and the container is evacuated to a pressure of about 1.3 Pa and heated at 40.degree. C.