Dechlorination of Carbon Tetrachloride by Fe(II) Associated with Goethite

Carbon tetrachloride (CT) was dechlorinated to chloroform (CF) under anoxic conditions by Fe(II) that was sorbed to the surface of goethite (α-FeOOH). No reaction occurred when Fe(II) was present and goethite was absent. Several abiotic experiments were conducted with goethite at 30 °C in which the total amount of Fe(II) in the system, the amount of sorbed Fe(II), the density of sorbed Fe(II), and the pH were varied. Regeneration of sorbed Fe(II) occurred when dissolved Fe2+ was available and maintained pseudo-first-order conditions with respect to CT. Analysis of the rates of CT loss for experiments with sorbed-Fe(II) regeneration showed the rate-determining-step to be first order with respect to CT, second order with respect to the volumetric concentration of sorbed Fe(II) (i.e., mmol sorbed Fe(II) L-1 suspension), and zero order with respect to H+ for pH between 4.2 and 7.3. The absolute rate constant for the reaction was determined to be 42 ± 5 M-2 s-1. Normalization of the observed rate constants to ...