Effects of Seepage Velocity and Temperature on the Dechlorination of Chlorinated Aliphatic Hydrocarbons

摘要

The influence of seepage velocity and groundwater temperature on the dechlorination rates of trichloroethylene (TCE) and tetrachloroethylene (PCE) by zero-valent iron (Fe0) were investigated by running laboratory column tests at seepage velocities ranging from 31 to 1,884 m/year at temperatures of 10 and 23°C. By increasing the seepage velocity from 31 to 1,884 m/year at 10°C, there were approximately seven- and nine-fold increases in the normalized dechlorination rate constants (SA) of TCE and PCE, respectively. Similarly, a four-fold increase in the SA of TCE and PCE was also observed at 23°C when increasing the seepage velocity from 103 to 1,183 m/year. Raising the groundwater temperature from 10 to 23°C at a given seepage velocity resulted in 2.7 and 1.1 times increases in the TCE SA and PCE SA, respectively. With the application of the Arrhenius equation, activation energies of 70.3 kJ/mol for TCE and 38.6 kJ/mol for PCE dechlorination were determined, indicating domination of the electron transfer process over the mass transfer as a major rate-limiting step of the dechlorination reactions by Fe0.