Removal of halogenated organic compounds in landfill gas by top covers containing zero-valent iron

Transformation of gaseous CCl3F and CCl4 by zero-valent iron was studied in systems unsaturated with water under anaerobic conditions-in an N-2 gas an d in a landfill gas atmosphere. The transformation was studied in batch as well as flow-through column tests. In both systems, the transformation proc ess of the compounds was pseudo-first-order. Transformation rate constants, referring to the water phase and normalized to 1 m(2) iron surface/mL., of up to 1100 mt m(-2) h(-1) (batch) and 200 mL m(-2) h(-1) (flow-through) we re found. The transformation was strongly dependent on pH and the presence of oxygen. During continuous aerobic conditions, the transformation of CCl3 F decreased toward zero. Model calculations show that use of zero-valent ir on in landfill top covers is a potential treatment technology for emission reduction of halogenated trace compounds from landfills.