Silicate Enhances the Long-Term Dechlorination Performance of Sulfidized Zero-Valent Iron: Trade-Off between...

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Sulfidized zero-valent iron (S-ZVI) is effective for chlorinated hydrocarbon remediation.
• S-ZVI faces challenges due to corrosion in high dissolved oxygen (DO) environments.
• Understanding S-ZVI aging is crucial for optimizing remediation strategies.

Purpose of the Study:

• To investigate the role of silicate in mitigating the passivation and oxidative corrosion of aged S-ZVI.
• To evaluate the impact of silicate on the dechlorination performance of aged S-ZVI for trichloroethylene (TCE).
• To elucidate the mechanisms by which silicate enhances the redox reactivity of aged S-ZVI.

Main Methods:

• Aging of S-ZVI under controlled conditions.
• Treatment of TCE-contaminated water with aged S-ZVI in the presence and absence of silicate.
• Electrochemical analysis to determine electron resistance.
• Analysis of reaction kinetics and degradation capacity.
• Characterization of surface species and dissolved species.

Main Results:

• Silicate addition significantly improved the dechlorination performance of aged S-ZVI.
• Silicate decreased electron resistance by 18.9% and increased oxidative dechlorination by 23.3%.
• The dechlorination rate constant and degradation capacity increased by 61.1% and 85.7%, respectively.
• Silicate promoted the depolymerization of silica, mitigating passivation and enhancing ferrous iron dissolution and ROS production.

Conclusions:

• Silicate acts as a crucial additive to balance the passivation and oxidative corrosion of aged S-ZVI.
• Silicate enhances both reductive and oxidative dechlorination pathways by promoting ROS generation.
• The findings offer novel strategies for developing robust S-ZVI-based remediation technologies.