Reductive dechlorination of tetrachloroethylene in soils by Fe(II)-based degradative solidification/stabilization

Area of Science:

• Environmental Chemistry
• Soil Science
• Remediation Technologies

Background:

• Conventional solidification/stabilization (S/S) immobilizes contaminants.
• Fe(II)-based DS/S enhances S/S by using Fe(II) as a reducing agent for chlorinated organics.
• Natural organic matter's potential interference with Fe(II) in DS/S needed investigation.

Purpose of the Study:

• To assess the feasibility of Fe(II)-based DS/S for treating tetrachloroethylene (PCE) contaminated soils.
• To evaluate the impact of natural organic matter on PCE degradation.
• To characterize the degradation kinetics and byproducts of PCE using this technology.

Main Methods:

• Conducted PCE degradation experiments in the presence of humic acid.
• Performed solid-phase degradation experiments to analyze PCE treatment in soils.
• Applied pseudo-first-order rate law to describe degradation kinetics.
• Identified and quantified chlorinated intermediates and byproducts.

Main Results:

• Fe(II)-based DS/S effectively degraded PCE in soils.
• Natural organic matter did not significantly interfere with the Fe(II) degradative reaction.
• PCE degradation followed pseudo-first-order kinetics with half-lives from 13 to 335 days.
• Trichloroethylene (TCE) was the primary, transitory chlorinated byproduct (<7% molar basis).
• Surface reaction kinetics controlled PCE degradation.

Conclusions:

• Fe(II)-based DS/S is a viable technology for treating PCE-contaminated soils.
• The technology offers effective contaminant treatment with manageable degradation rates for in-situ applications.
• Minimal production of harmful chlorinated intermediates suggests a favorable environmental profile.