TRANSFORMATION OF CARBON-TETRACHLORIDE BY PYRITE IN AQUEOUS-SOLUTION

The reactivity of CCl4 with pyrite was investigated by measuring the CCl4 transformation rates and products under aerobic and anaerobic conditions. Under all reaction conditions, >90% of the CCl4 was transformed within 12-36 days in the presence of 1.2-1.4 m(2)/L pyrite at 25 degrees C. A zero-order dependence on the CCl4 concentration supports a surface-controlled reaction mechanism wherein the rate of reaction depends on the absorbed CCl4 concentration. In aerobic systems >70% of the CCl4 was transformed to CO2 whereas in a fresh-ground/anaerobic pyrite system approximately 50% of the CCl4 was transformed to CHCl3. X-ray photoelectron spectroscopy of the reacted pyrite showed that an FeOOH coating formed on the surface under aerobic conditions. Under all reaction conditions, the pyrite surface was depleted of ferrous iron.