Sorption of fission product radionuclides,¹³⁷Cs and⁹⁰Sr, by Savannah River Site sediments impregnated with colloidal silica

Abstract

Permeation grouting with colloidal silica gel is a potentially effective means for creating hydraulic barriers to prevent the advective migration of radioactive contaminants in shallow permeable sediments. However, the effectiveness of silica gel grouted barriers in controlling transport of fission product radionuclides through sorption and diffusion is unknown. To resolve this question, static-batch sorption measurements with Cs + and Sr 2+ were conducted at ambient temperature (23 • C) and for times up to 96 days on silica gel and on two kaolinitic sediments from the Savannah River Site in South Carolina. Sorption experiments on the latter were conducted both in the presence and in the absence of silica gel. Cesium and strontium concentrations were varied between 10 −3 to 10 −8 M (mol/L) and 10 −4 to 10 −8 M, respectively. The pH values after one day varied for each experiment and ranged from 3.6 to 6.6. The pH of the solutions were, however, buffered by the sediments and/or silica gel, and changed little over the duration of the experiments. The fraction of both cesium and strontium retained on the solids increased with decreasing radioelement concentration. The sorption data were fitted to the Freundlich isotherm model.

Kinetic and thermodynamic investigations of strontium ions retention by natural kaolinite and clinoptilolite minerals

“…[3][4][5][6][7][8][9][10][11][12][13][14][15]. Although these studies have provided valuable information about various macroscopic and microscopic aspects of the fixation behavior of this ion, only a limited area was devoted to reveal the kinetic and thermodynamic characteristics of the sorption process.…”

“…Another work have also estimated that the organic-inorganic complex made up of kaolinite particles coated with humic substances, plays an important role in the behavior of various ions (including Sr 2+ ) in the environment [6]. In a study to reveal the effect of loading on the sorption of strontium by kaolinite, it was stated that the fraction of this element retained on the solids increased with decreasing radio-element ( 90 Sr) concentration and that the sorption data were fitted to the Freundlich isotherm model [7]. Microscopically, quantitative analyses of Sr-loaded kaolinite samples using EXAFS showed a single first shell of 9-10 (±1) oxygen atoms surrounding sorbed strontium at an average Sr−O bond-distance of 2.61 (±0.02) Å, indicating hydrated surface complexes [8].…”

Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils

“…Following more than 60 years of nuclear power generation, and a longer history of nuclear research, many legacy waste sites with stored radioactive wastes exist throughout the world. Such legacy sites include Sellafield (Cumbria, UK), 1 Savannah River (NC, USA), 2 and the Little Forest Legacy Site (NSW, Australia). 3,4 The location for such sites was often chosen based on the local geology and soil composition.…”

“…3,4 Despite the clay-rich environments, radioactive contaminants (including fission products such as strontium and caesium, and actinides) have been detected in sediments, groundwater, surface runoff and vegetation surrounding such legacy sites. 1,2,[4][5][6][7] Furthermore, nuclear incidents such as the Fukushima Daiichi nuclear disaster have resulted in fission products, including caesium, entering the environment. [8][9][10][11][12][13] Transport of fission products like caesium(Cs) and strontium (Sr) through the environment is heavily impacted by the soil mineralogy (including clay minerals and metal oxides in the soils at the Little Forest Legacy Site 3,4,7 ), their surface speciation and complexation with organic matter.…”

Uranium-rich opal from the Nopal I uranium deposit, Peña Blanca, Mexico: Evidence for the uptake and retardation of radionuclides

“…This property of colloidal silica is used in growth experiments of single crystals, where the slow diffusion of ionic species limits the number of seed crystals (Henisch, 2005), and in the containment of ionic species in contaminated sites where colloidal silica is used as a barrier material (Hakem et al, 2004). Dugger et al (1964) examined the adsorption of cations on terminal silanol groups in colloidal silica.…”