Reductive dechlorination of carbon tetrachloride in acidic soil manipulated with iron(II) and bisulfide ion

Batch and column tests were conducted to investigate the effect of reductant concentration, reductant contact time, and suspension pH on reductive dechlorination of carbon tetrachloride (CT) by soil manipulated with Fe(II) and HS−. Kinetic rate constants for the reductive dechlorination increased as the reductant concentrations increased. Fe(II) was more effective reductant than HS−, resulting in higher rate constants. The contact time of 1 day for the soil with HS− and that of 4 h with Fe(II) showed the highest reaction rates, respectively. The kinetic rate constants increased as the pH of soil suspensions with Fe(II) (5.2-8.0) and HS− (8.3-10.3) increased. Soil column with Fe(II) showed larger bed volumes (13.8) to reach a column breakthrough than that with HS− (4.0). Fe(II) treatment showed better removal of CT in the soil column with the addition of CaO than HS− treatment did. In contrast, HS− treatment not producing toxic products could be considered as an environmentally favorable reductant.