Her Majesty the Queen in Right of Canada, As Represented by the Minister

Minister of National Defence of Her Majesty's Canadian Government

Jack G Pagotto

Septimus H Liang

Brian H Harrison

A novel organic amine-impregnated activated carbon composition is disclosed which may be used in breathing gas filters to enhance removal of various toxic perfluorocarbons. Three processes for impregnating activated carbon with organic amines are also disclosed. One of these processes comprises the steps of placing the amine in contact with substantially dry activated carbon, subjecting the carbon and amine to an environment devoid of oxidizing gases or vapors (such as oxygen gas), and then heating the carbon and amine for an extended period while maintaining this oxidizer-free environment. Pretreatment procedures to enhance both the shelf-life and service-life of the amine-impregnated activated carbon are also disclosed.

Organic amine impregnated activated carbon

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.

Preparation of low chromium active charcoal by freeze drying impregnated

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. for two to three days until the amine compound is no longer visible on the carbon. The resulting TEDA impregnated carbon provides improved protection against toxic gases compared to the precursor charcoal.

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Nepean, Canada

Jack G Pagotto