| abstract |
A purifying agent and a purification method for use in efficiently removing noxious halogen-containing gases such as fluorine, chlorine, boron trifluoride, boron trichloride, tungsten hexafluoride and silicon tetrachloride which are contained in an exhaust gas from a process for semiconductor production. The purifying agent is prepared by impregnating a charcoal with an alkali metal formate and/or an alkaline earth metal formate or by impregnating a charcoal with an alkali metal hydroxide and/or an alkaline earth metal hydroxide together with an alkali metal formate and/or an alkaline earth metal formate. Noxious halogen-containing gases in an exhaust gas can be removed with good efficiency by contacting the purifying agent with the exhaust gas, and desorption from the purifying agent occurs scarcely. The safety and the efficiency of purification treatment can be further improved by disposing a purifying agent containing, as an active component, a metal oxide or a metal hydroxide as an active component as a former purifying agent and disposing a purifying agent prepared by impregnating a metal oxide with sodium formate as a latter purifying agent. |