Adsorption and kinetic behavior of uranium and thorium in seawater-sediment system

• Published in: Journal of radioanalytical and nuclear chemistry 2013, Vol.295 (1), p.649-656
• Main Authors: Kumar, Ajay, Singhal, R. K., Rout, Sabyasachi, Narayanan, Usha, Karpe, Rupali, Ravi, P. M.
• Format: Article
• Language: English
• Subjects: Adsorption; Analysis; Chemistry; Chemistry and Materials Science; Diagnostic Radiology; Hadrons; Heavy Ions; Inorganic Chemistry; Nuclear Chemistry; Nuclear Physics; Physical Chemistry; Sea-water; Sediments (Geology); Uranium
• ISSN: 0236-5731; 1588-2780
• DOI: 10.1007/s10967-012-1825-8

The adsorption and kinetic mechanism of uranium (U) and thorium (Th) in seawater-sediments system of Mumbai Harbour Bay (MHB) has been studied by K d values of two sets of experimental determinations using a batch experiment. After equilibrium time (7 days), under static conditions, K d for U and Th ranged from 25,030 to 55,662 mL/g (mean: 42,140 mL/g) and 24,926 to 38,561 mL/g (mean: 34,256 L/kg), respectively. Extraction studies showed that both U and Th were strongly bound to sediment components due to insignificant difference in their mean concentration in equilibrium solution. Rate constants ( k ) for transfer between seawater and the exchangeable fraction were found to be similar for the sediments as 1.02 ± 0.03 day −1 for uptake of U and Th. The resulting adsorption data were fitted to Freundlich, linear and Langmuir isotherm models. All the three models showed a significant correlation ( R 2 >0.9), indicating that there is more complex relationships with adsorption behavior of U and Th on sediment surface. Since, the Freundlich constant ( n ) for U and Th was found to be closer to unity. Therefore linear model was observed to be highly suitable. Based on the linear model, the distribution coefficient ( k d ) of Th was about 1.5 times higher than U. According to Freundlich model, sorption of U in sediments observed to be higher than Th. However, Langmuir model considered in opposite to Freundlich and showed a higher value of K L constant for Th than U. The pH (water) of the sediments ranged from 7.8 to 8.2 and the estimated total carbon (determined by C H N S–O elemental analyser) ranged from 1.7 to 3.4 %.