Colloid Mobilization in the Field Using Citrate to Remediate Chromium

• Published in: Ground water Vol. 39; no. 6; pp. 895 - 903
• Main Authors: Johnson, Carol R., Hellerich, Lucas A., Nikolaidis, Nikolaos P., Gschwend, Philip M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-11-2001; National Ground Water Association; Ground Water Publishing Company
• Subjects: Chelating Agents - chemistry; Chromium; Chromium - chemistry; Citrates; Citric Acid - chemistry; Colloids; Colloids - analysis; Colloids - chemistry; Environmental aspects; Environmental remediation; Environmental services industry; Finishing; Geologic Sediments - chemistry; Groundwater; Hydrogen-Ion Concentration; Hydrology; Metal products industry; Metals; Pollution control industry; Sediments; United States; Water Pollutants, Chemical; Water pollution; Water Pollution - prevention & control; Water Purification; Water treatment; Water, Underground; United States
• ISSN: 0017-467X; 1745-6584
• DOI: 10.1111/j.1745-6584.2001.tb02477.x

We investigated the feasibility of cleaning aquifer sediments, long contaminated with chromium (Cr) from a metal plating facility, by detaching colloid‐sized sorbents from the immobile aquifer solids and then pumping those colloids to the surface for treatment. In laboratory experiments using aquifer solids from the site, several solutions (water at various pHs, phosphate, oxalate, ascorbate, citrate) were examined for their ability to disperse colloids and Cr. Based on these tests, a 5 mM citrate solution at pH 7 was selected. Subsequently, such a citrate solution was used in the field in two single‐well injection‐withdrawal experiments. Large quantities of colloids were released immediately after injection. The colloidal particles mobilized by citrate in the field had more than 20 times higher Cr concentrations than did the average aquifer sediments, implying success in mobilizing Cr‐associated phases. Further, laboratory and field tests showed that anion exchange of citrate for chromate caused some additional release of Cr from these aquifer solids.