Treatment of waste containing EDTA by chemical oxidation

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent that has been e xtensively used to enhance the solubilization of heavy metal cations and re lease of EDTA contributes to environmental problems. EDTA is recalcitrant t o microbial metabolism and chemical oxidation is considered a possible meth od of remedial treatment. The use of the commercially available process of MIOX Corporation generates mixed oxidants on site and this solution is mark edly effective in the destruction of the chelating characteristic and the d ecarboxylation of EDTA. When measuring the release of C-14 from carboxyl la beled EDTA, the mixed oxidant solution was comparable to the Fenton's react ion over a broad pH range. The presence of Mn2+, Cr3+, Or Fe3+ at levels eq ual to that of EDTA stimulated the rate of EDTA decomposition; however, the rate of EDTA breakdown was inhibited when the concentration of Cr3+ or Mn2 + exceeded the concentration of EDTA. The treatment pf Co2+-EDTA or Cu2+-ED TA with mixed oxidants in the presence of ultra violet light resulted in th e loss of chelation ability of EDTA. In the absence of chelated metals, ove r 75% of the chelation property of a 70 mM EDTA solution was destroyed in 4 5 min. The reaction products resulting from the use of mixed oxidants added to EDTA were non-toxic to bacteria and should not contribute to additional environmental problems. (C) 1999 Elsevier Science Ltd. All rights reserved .