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  • 1 Department of Chemistry and Biochemistry, The Florida State University Tallahassee, FL-32306, USA; On leave from Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai - 400 085, India
  • 2 Department of Chemistry and Biochemistry, The Florida State University Tallahassee, FL-32306, USA
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Summary  

Batch sorption experiments of cesium, Cs+, on SiO2 . xH2O (silica gel) have been conducted with variable times of equilibration, amounts of silica gel (0.10-1.00 g), cesium concentrations (5.00 . 10-5-2.40 . 10-3M), ionic strengths (0.20-1.40M NaClO4), pH (2.50-7.70), and temperatures (273-333 K). The diffusion coefficient of Cs+ ion was calculated to be (9.19±0.86) . 10-11 m2 . s-1 under particle diffusion-controlled conditions. The sorption rate was (3.94±0.65) . 10-3 s-1 at 298 K, pH 7.70±0.05 in 0.20M NaClO4. The sorption data fits the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Cesium sorption on 0.20 g silica gel decreased with ionic strength from (40.42±0.34)% in 0.20M NaClO4 to (6.35±0.40)% in 1.40M NaClO4, at pH(initial) 8.20±0.05. A gradual decrease in pH with increased ionic strength is consistent with a cation-exchange mechanism. Sorption of Cs+ on silica gel decreased with increased temperature, indicating an exothermic enthalpy. The presence of anions such as fluoride, carbonate, phosphate and oxalate in the aqueous medium did not influence the cesium sorption profile.