Removal of radiocobalt from EDTA-complexes using oxidation and selective ion exchange

Abstract

Methods for the removal of radiocobalt from an ethylenediaminetetraacetic acid (EDTA) complex of Co(II) (aqueous solution containing 10 microM Co(II) and 10 microM or 50 microM EDTA traced with (57)Co) are presented. The studies examined a combination of different oxidation methods and the sorption of (57)Co on a selective inorganic ion exchange material, CoTreat. The oxidation methods used were ultraviolet (UV) irradiation with and without hydrogen peroxide (H(2)O(2)), as well as ozonation alone or in combination with UV irradiation. Also, the possible contribution of Degussa P25 TiO(2) photocatalyst to degradation of EDTA was studied. The best results for the equimolar solution of Co(II) and EDTA were achieved by combining ozonation, UV irradiation, Degussa P25 TiO(2) and CoTreat, with approximately 94% sorption of (57)Co. High values for the (57)Co sorption were also achieved by ozonation ( approximately 88%) and UV irradiation (approximately 90%) in the presence of CoTreat and Degussa P25 TiO(2). A surplus of EDTA over Co(II) was also tested using 10 microM Co(II) and 50 microM EDTA. Only a slight decrease, to approximately 88% sorption of (57)Co, was detected compared to the value (approximately 90%) obtained with 10 microM EDTA.

Capture of Co(II) from its aqueous EDTA-chelate by DTPA-modified silica gel and chitosan

“…The Co(II) removal efficiencies of DTPA-silica gel and -chitosan in the Co(II):EDTA 1:2 solution were 96.3% and 93.8%, and in 1:10 solution they were 67.8% and 90.2%, respectively. For comparison, 97% removal of Co(II) was achieved by Malinen et al [11] using titanium antimonates in the Co(II):EDTA 1:2 system, while only 7% removal was obtained using CoTreat in a Co(II):EDTA 1:1 system [30].…”

“…Thus, it is obvious that, besides binding Co(II) ions, DTPA-silica gel and -chitosan were able to bind either Co(II)EDTA-chelates or capture Co(II) from dissolved metal EDTA species (see Sections 3.3 and 3.4). This result is promising because the highly Co(II) specific adsorption material CoTreat can bind Co(II) only in ionic form [11,30].…”

Novel Cu(II)–EDTA Decomplexation by Discharge Plasma Oxidation and Coupled Cu Removal by Alkaline Precipitation: Underneath Mechanisms

“…7−12 Decomplexation would release free heavy metal ions into solutions, allowing further removal of free metal ions using postprecipitation method. Some classical oxidation methods such as ultraviolet (UV)/H 2 O 2 , 7,8 Fenton oxidation, 9 ozonation, 10 TiO 2 photo-catalysis 11 and photoelectrocatalytic oxidation, 12 have been used for decomplexation. However, one single oxidation technique usually did not give high decomplexation efficiency.…”

“…Decomplexation is proved to be essential to achieve high-efficient elimination of the chelating complexes, which could be achieved by strong oxidation techniques. − Decomplexation would release free heavy metal ions into solutions, allowing further removal of free metal ions using postprecipitation method. Some classical oxidation methods such as ultraviolet (UV)/H 2 O 2 , , Fenton oxidation, ozonation, TiO 2 photocatalysis and photoelectrocatalytic oxidation, have been used for decomplexation. However, one single oxidation technique usually did not give high decomplexation efficiency.…”

“…There was high selectivity for ozone to react with organic compounds, the oxidative potential of direct ozone oxidation was relatively poor, and thus it was usually combined with other methods or materials. Malinen reported that it was necessary to combine ozone and UV to realize high-efficient decomplexation for Co–EDTA. Photocatalysis was also applied to decompose the chelating complexes; however, light absorptivity of TiO 2 restrained its utilization in practical application .…”