REDUCTIVE DECHLORINATION OF CARBON-TETRACHLORIDE WITH ELEMENTAL IRON

Carbon tetrachloride (CCl4 ) as abiotically dechlorinated to chloroform (CHCl3) and methylene chloride (CH2Cl2) by zero valent iron (Fe-0). Dechlorination of CCl4 was rapid, and approximately followed first-order kinetics in the range of concentrations tested (CCl4: 1.5-5.5 mu M; Fe-0 powder: 1-10g per 265 ml distilled water). Initial dechlorination rate coefficients for anoxic batch reactors (0.290 +/- 0.009 h(-1) for 1 g Fe-0; 1.723 +/- 0.078 h(-1) for 10 g Fe-0) increased with iron surface area (initially 2.4 +/- 0.2m(2)/g). Rate coefficients also increased with time, probably because of an increase in; reactive surface area due to cathodic depolarization and pitting of the iron surface. Dechlorination also occurred under oxic conditions, although the rates were significantly slower (e.g., 0.085 +/- 0.041h(-1) for 1g Fe-0 and initial dissolved oxygen 7.4mg/l). A rapid pH increase was synchronous to dissolved oxygen consumption, and the pH remained constant after the oxygen was depleted. This was attributed to the proton and oxygen consuming aerobic corrosion of the Fe-0 surface. The potential for developing remediation technology with Fe-0 is discussed.