Plutonium-239+240 selectivity for pseudo-colloids of iron in subsurface aquatic environment having elevated level of dissolved organic carbon

• Published in: Journal of radioanalytical and nuclear chemistry Vol. 280; no. 1; pp. 141 - 148
• Main Authors: Singhal, R. K., Karpe, Rupali, Muthe, K. P., Reddy, A. V. R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-04-2009
• Subjects: Chemistry; Chemistry and Materials Science; Diagnostic Radiology; Hadrons; Heavy Ions; Inorganic Chemistry; Nuclear Chemistry; Nuclear Physics; Physical Chemistry; Zeta Potential; Plutonium; Humic Acid; Dissolve Organic Carbon Concentration; Alpha Spectrometry
• ISSN: 0236-5731; 1588-2780
• DOI: 10.1007/s10967-008-7390-5

Laboratory simulated experiments have been conducted to study the association of
239,240
Pu with pseudo-colloids of iron in groundwater samples having dissolved organic carbon (DOC) in the range of 10–60 mg L
−1
. Ultra-filtration membranes have been used to partition colloidal components into seven different size range of <0.45 μm-1.1 nm. Elevated levels of Fe, DOC and
239,240
Pu were observed in the fractions concentrated with 1.6 nm (10,000 NMWL) and 1.1 nm (500 NMWL) compared to the other dissolved fractions. To ascertain the fact that, the formation of pseudo-colloids of Fe in the size range 1.6 nm and 1.1 nm was assisted by the presence of DOC, experiments have been conducted under similar experimental conditions with uniform Fe concentration and varying the DOC in the range of 10–60 mg L
−1
. Seven to eight times higher concentration of Fe was observed in fractions concentrated with 1.6 nm and 1.1 nm having DOC ≥30 mg L
−1
, whereas Fe was equally distributed in all the fractions in groundwater having DOC ≥10 mg L
−1
. The surface morphology and composition of the residue left on the ultra-filtration membranes was examined using scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometer (EDS). The EDS results validate the observation that the residue left on filter paper membrane of 10000 and 500 NMWL with pore size 1.6 and 1.1 nm respectively, shows elevated levels of carbon and Fe contents as compared to other fractions. Understanding the association of
239,240
Pu with Fe and DOC will facilitate in predicating the long term integrity of underground waste storage facilities of alpha emitting radioactive material.