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Colloid mobilization in the field using citrate to remediate chromium
C R Johnson1, L A Hellerich, N P Nikolaidis
1Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge 02139, USA.
Ground Water
|November 16, 2001
Summary
Citrate effectively mobilizes chromium-contaminated colloids from aquifer sediments. This novel approach detaches and concentrates chromium-laden particles for efficient surface treatment, offering a promising solution for groundwater remediation.
Area of Science:
- Environmental Science
- Geochemistry
- Water Treatment
Background:
- Aquifer sediments are often contaminated with heavy metals like chromium (Cr) from industrial activities.
- Conventional remediation methods can be costly and inefficient for removing contaminants sorbed to immobile aquifer solids.
Purpose of the Study:
- To investigate the feasibility of cleaning chromium-contaminated aquifer sediments by mobilizing colloid-sized sorbents.
- To evaluate the effectiveness of different solutions in dispersing chromium and colloids from aquifer solids.
Main Methods:
- Laboratory experiments using aquifer solids to test various solutions (water, phosphate, oxalate, ascorbate, citrate) for colloid and Cr dispersion.
- Field application of a selected citrate solution (5 mM, pH 7) in single-well injection-withdrawal tests.
- Analysis of Cr concentrations in mobilized colloids and aquifer sediments.
Main Results:
- A 5 mM citrate solution at pH 7 effectively dispersed colloids and chromium in laboratory tests.
- Field experiments showed immediate release of large quantities of colloids upon citrate injection.
- Mobilized colloids exhibited over 20 times higher Cr concentrations than average aquifer sediments.
- Anion exchange between citrate and chromate further enhanced chromium release.
Conclusions:
- Citrate-based colloid mobilization is a feasible strategy for chromium remediation in contaminated aquifers.
- This method successfully concentrates chromium-associated phases onto mobile colloids for surface treatment.
- The findings suggest a potentially more efficient approach to groundwater and sediment cleanup.
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