Reductive dechlorination of chlorinated hydrocarbons using iron(II) and modified green rusts in degradative solidification/stabilization

Degradative solidification/stabilization (DS/S) is an attractive alternative for soils and sediments polluted by multiple contaminants, especially those contaminated with heavy metals and chlorinated aromatic hydrocarbons (CAH). Several reductants were synthesized by modifying green rust (GR) and Fe(II) precipitates with cement extracts and cement elements. The activity of the synthesized agents for degrading perchloroethylene (PCE) was evaluated. Reductive dechlorination of 2,2′,3,3′,4,4 ′-hexachlorobiphenyl (HCB) in ferrous iron/Portland cement system was characterized.; Portland cement extract (PCX), Portland cement suspension (PC) and some cement element solutions significantly enhance the activity of GR_Cl and Fe(II)-based reductant in reducing PCE. Modified GRs and modified Fe(II)-based reductants were found to be attractive potential active agents for the DS/S system.; Reductive dechlorination of HCB by GR and Fe(II) in a 10% Portland cement slurry was characterized using batch slurry reactors. The effects of GR _Cl dose, pH and modifying agents were investigated for dechlorination of HCB by GR in cement slurry. A pseudo second-order rate law was used to analyze these data.; The effects of Fe(II) dose, pH, reaction temperature, initial HCB concentration and modifying agents were examined for the dechlorination of HCB by Fe(II) in cement slurry. A pseudo first-order rate law was used to analyze the kinetic data for these experiments. Based on the results of initial HCB concentration experiments, a saturation model was also discussed to describe the kinetics of HCB degradation by Fe(II) in cement slurry. The temperature effect was discussed using Arrhenius equation and the Arrhenius plot was non-linear. Chlorines were most easily removed from HCB in the order meta > ortho > para.; HCB dechlorination by both GR and Fe(II) in cement slurry is strongly dependent on pH. The optimum values of pH for GR and Fe(II) in cement slurry were similar regardless of target compound.