Sorption of Trichloroethylene and Tetrachloroethylene in a Batch Reactive Metallic Iron-Water System

Abstract

Sorption and reduction kinetics of trichloroethylene (TCE) and tetrachloroethylene (PCE) with metallic (zero-valent) iron were determined in a closed, well-mixed, anaerobic batch system by measuring aqueous and total system concentrations of the respective chlorinated solvent as a function of time. The reaction orders with respect to TCE and PCE total system concentrations were 2.7 and 1.3, respectively, indicating that the reaction mechanisms are complex. Both compounds exhibited nonlinear sorption behavior and could be fitted by the generalized Langmuir isotherm expression. After accounting for the mass sorbed to the iron, the reduction rates of PCE and TCE are first-order. This indicates that the bulk of sorption is to nonreactive sites. Competitive sorption was observed when both PCE and TCE were present ; however, no competition for reaction was detected. The design and study of treatment systems for chlorinated solvents using metallic iron requires consideration of sorption processes.