ELECTRON-BEAM DEGRADATION OF CHLORINATED HYDROCARBONS IN AIR

Using a low-energy electron accelerator (180 keV, 3 kW) synthetic air polluted with chlorinated hydrocarbons such as cis-dichloro-, trichlor o- and perchloroethene was irradiated in a flow system. Already at dos es of 2.5 kGy, more than 90 vol% of the initial pollutant concentratio n (2 - 50 ppm) could be removed. As main products HCl, CO, chlorometha nes, chloroacetyl chlorides and phosgene were identified. After hydrol ysis of phosgene and chloroacteyl chlorides in a wet scrubbing system, the chlorine balance shows nearly complete mineralization of the poll utants to HCl, CO and CO2. Less than 5 vol% of chloromethanes and abou t 0.1 vol% chloroacetic acids were detected after irradiation and hydr olysis. An attempt is made to describe the degradation mechanism as OH radical induced chain reaction. The OH radical adds to the ethene dou ble bond. The resulting adduct releases a chlorine radical. In presenc e of oxygen a chain reaction is initiated by this radical, which leads to decomposition of the chloroethenes.