Photothermal destruction of the vapor of organic compounds

The results of thermal and photothermal destruction of the vapors of organic compounds were compared by conducting tests in a photothermal detoxification unit. A xenon arc lamp was used as the irradiation source. The tests were conducted on trichlorethylene (TCE), 1,2-dichlorobenzene (DCB), and a mixture of benzene, toluene, ethyl benzene and m-xylene (BTEX). These materials represent various types of common pollutants at contaminated sites. The results showed that both TCE and DCB can be destroyed photothermally at much lower temperatures than in a pure thermal process. The photothermal effect of xenon arc radiation on BTEX was also clearly shown for all components except benzene; the effect was not as great as that on the chlorinated compounds. Carbon tetrachloride from TCE was the only significant product of incomplete conversion observed in all experiments. The absorption spectra of these six compounds were taken at various temperatures using a custom-built high-temperature absorption spectrophotometer. The absorption strength, rate of photon absorption, and photothermal quantum yields of these six compounds all increased with temperature. The predicted radiant intensities of the mercury arc lamp and the predicted temperatures of the reactor for the complete mineralization of TCE, DCB and toluene were estimated using a mathematical model. The results showed that a mercury arc lamp with relatively low radiant intensity is capable of destroying 99% of various categories of organic pollutants at moderate temperatures. This makes the process ideal for non-combustion on-site destruction of the off-gas from remediation technologies such as soil vapor extraction, thermal desorption and air stripping.