Surfactant enhanced remediation of subsurface chromium contamination

The objective of this research was identification of optimal surfactant systems for remediating chromate-contaminated subsurface environments. Batch and column studies were conducted utilizing chromium contaminated soil obtained from the U.S. Coast Guard Support Center, Elizabeth City, N.C. Results of the batch studies demonstrated that surfactants, when used alone, were able to enhance the extraction of chromate 2.0-2.5 times greater than water. When a complexing agent, diphenyl carbazide, was solubilized by aqueous micelles the system was able to enhance the chromate elution by 9.3 to 12.0 times greater than water (or 3.7-5.7 times greater than surfactant without the complexing agent). Column studies showed that when surfactants are used along with the complexing agent, 213% of Cr(VI) can be removed relative to D.I. water in less than 20 pore volumes, whereas D.I. water took 35 pore volumes to reach the baseline removal. The economics of surfactant enhanced subsurface remediation will be affected by surfactant losses (e.g. precipitation and sorption); batch and column studies were conducted to evaluate the losses of surfactants due to such phenomena. Results of these laboratory studies demonstrated that the surfactant system containing Dowfax 8390 and diphenyl carbazide was most effective in remediation of the chromium contaminated soil.