PCE DNAPL degradation using ferrous iron solid mixture (ISM).

Area of Science:

• Environmental Chemistry
• Remediation Technologies
• Geochemistry

Background:

• Tetrachloroethene (PCE) is a common groundwater contaminant, often present as a dense non-aqueous phase liquid (DNAPL).
• Effective remediation strategies are needed to address PCE contamination in subsurface environments.

Purpose of the Study:

• To synthesize and evaluate a ferrous iron solid mixture (ISM) for PCE DNAPL degradation.
• To develop and validate a method for measuring PCE concentrations in aqueous and non-aqueous phases.
• To elucidate the degradation kinetics and pathways of PCE by ISM.

Main Methods:

• Synthesis of ferrous iron solid mixture (ISM) containing Fe(II), Fe(III), and Cl.
• Development of a methanol-hexane extraction procedure for PCE quantification.
• Kinetic experiments monitoring PCE and its degradation products under varying conditions.
• Development of a kinetic model to describe observed degradation patterns.

Main Results:

• ISM effectively dechlorinates PCE, with degradation rates dependent on total PCE concentration and Fe(II) content.
• PCE degradation followed first-order kinetics in the absence of DNAPL and a linear decrease with total PCE concentration when DNAPL was present.
• Trichloroethylene (TCE) was a major intermediate, suggesting slower degradation of TCE by ISM.
• Detection of ethene, acetylene, and ethane indicated hydrogenolysis and beta-elimination as degradation pathways.

Conclusions:

• The synthesized ISM shows promise for PCE DNAPL remediation.
• The degradation mechanism involves multiple pathways, influenced by Fe(II) concentration and PCE phase.
• Further research may be needed to optimize ISM for complete degradation of chlorinated intermediates like TCE.