Iron-Mediated Aeration: Evaluation of Energy-Assisted Enhancement for In Situ Subsurface Remediation

Laboratory tests using ultraviolet radiation and sonocation energy were found to kinetically enhance an iron-mediated aeration (IMA) process under development to remove chelated metals and radionuclides and associated organics, from groundwater and soils. A model inorganic contaminant (Cd2+) chelated with ethylenediamine tetraacetic acid (EDTA) was used. The IMA process breaks the complex, releasing the target metal for removal. Overall experimental results indicate that the EDTA degradation mechanism can be accelerated compared to nonenergized IMA, by a factor of 2 using sonocation energy and by a factor of 3-4 using photochemical energy at circumneutral pH. No differences in the by-products were indicated in chemical analyses. For both sonocation and photochemical tests, the major breakdown products detected were glyoxylic acid and formaldehyde. Only minor amounts of larger molecular weight species (iminodiacetic acid, nitrilotriacetic acid, and ethylenediamine triacetic acid) were detected.