The mechanisms for chemical adsorption of trichloroethylene (TCE) to iron surfaces were studied using periodic density functional theory (DFT). DFT modeling of adsorbed species was performed using the generalized gradient approximation with the Perdew-Burke-Enzerhof (PBE) functional. Chemisorption structures were obtained for four adsorbed initial configurations. Di-sigma C-Fe and Cl-Fe complexes were formed by initial configurations with two carbon (C-bridge) or two chlorine atoms (Cl-bridge) adsorbed at bridge sites between adjacent iron atoms, respectively. Calculated binding energies indicated that chemisorption was highly exothermic, with the complex formed at the C-bridge site being the most energetically favorable. Chemisorption at the C-bridge site had an early transition state in which all three C-Cl bonds were activated from ∼ 1.7 to ∼ 2.2 Å, with an activation energy of 50 kJ/mole. The early transition state and the loss of all three Cl atoms upon chemisorption were consistent with most experimental observations that TCE undergoes complete dechlorination in one interaction with the iron surface. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 1/04/2005).