Authors:
R. Singhal Bhabha Atomic Research Center Trombay Environmental Studies Section/Health Physics Division Mumbai 400085 India

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S. Joshi Bhabha Atomic Research Center Trombay Environmental Studies Section/Health Physics Division Mumbai 400085 India

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A. Hegde Bhabha Atomic Research Center Trombay Environmental Studies Section/Health Physics Division Mumbai 400085 India

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Abstract  

The purpose of the present study is the association of natural uranium in seawater with colloidal and suspended-particulate matter was determined. The separation of suspended particulate material (>0.45 µm) and colloidal fraction (as dissolved fractions) in seawater were done by suction and ultra filtration techniques. Seawater samples were collected at 1 km away from the shore and subjected to sequential fractionation in nine stages ranging from 2.7 µm to 1.1 nm. Suspended particulate matter were separated in three different size groups namely >2.7 µm, <2.7–>0.45 µm and <0.45–>0.22 µm by suction filtration using cellulose acetate and nitrate membranes filters. To concentrate the solution with colloidal particles <0.22 µm–1.1 nm (0.5 k Nominal Molecular Weight cut-off Limit {NMWL}), the solution obtained from filtration through <0.22 µm was passed through stirred ultra-filtration cell. The pH and conductivity at different stages of fractionation (dissolved) showed minor variations. The concentration of uranium was measured in suspended and dissolved fractions by using a pulsed nitrogen laser at 337.1 nm. In order to evaluate the role of mineral colloids in various stages of filtration, concentration of calcium, magnesium, potassium were measured by using ion chromatography and atomic absorption spectrometry. The clay mineral at seawater pH (approximately 8) behave as negative ions and provides binding site for the positively charge species of uranium. Among the dissolved fraction, the maximum concentrations of colloidal uranium was observed about 4 times higher than that compared to average concentration of 6.93±3.10 ppb in other fractions. In the case of suspended particulate matter, the concentration of uranium was below detection limits (<1 ppb). The maximum concentration of Ca, Mg and K in the dissolved fraction were in the <1.1 nm fraction, while for suspended particulate matter, the concentration of Ca, Mg and K decreased with the decrease in size and it is highest in the fraction of 0.22 –0.45 µm.

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Journal of Radionalytical and Nuclear Chemistry
Language English
Size A4
Year of
Foundation
1968
Volumes
per Year
1
Issues
per Year
12
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 0236-5731 (Print)
ISSN 1588-2780 (Online)