Sorption of Cs, Ba, Co, and Eu onto biotite: experiments and modelling
Licentiatavhandling, 2023
At 25°C, the measured sorption distribution coefficients (Rd -values) for 0.001 M were (pH 5-9): (Cs) 0.6-1.2, (Ba) 0.3-8.3, (Co) 0.01-1.9 and (Eu) 2.7-18 m3/kg, respectively. For I = 0.01 M, the corresponding results were (Cs) 0.1-0.7, (Ba) 0.01-4.4, (Co) 0.01-7.5 and (Eu) 0.2-4.3 m3/kg, respectively. For I= 0.1M, the corresponding results were (Cs) 0.01-0.2, (Ba) 0.03-0.4, (Co) 0.01-4.7 and (Eu) 2.1-6.7 m3/kg.
The surface acidity constants for the amphoteric surface site of biotite mineral were determined with the continuous potentiometric titration on a biotite suspension to pKa1= 0.30 and pKa2 = 0.20. These acidity constants were obtained by fitting titration data through the use of PHREEQC and PYTHON code optimization routines.
The biotite size fraction of 0.25-0.5 mm was characterized for acidic site density (ASD), cation exchange capacity (CEC) and the specific surface area (SSA) and were determined to be 6.7mmol/m2, 1.01 0.03 meq/100g and 0.47 m2/g by using tritium uptake, ammonium acetate (NH4Ac), and Kr-BET adsorption methods, respectively.
To model the experimental sorption data, PHREEQC geochemical modelling software coupled with PYTHON code optimization routines was used. The results shows that a two-step protolysis (2-pKa) non-electrostatic model (NEM) representing edge site with one additional ion-exchange site representing basal plane site is sufficient to reproduce the data for all four metals.
Cs
Biotite
Ba
titration
Eu
Co
Surface Complexation
Sorption
Författare
Pawan Kumar
Chalmers, Kemi och kemiteknik, Energi och material
A literature review on thermodynamic sorption models of radionuclides with some selected granitic minerals
Frontiers in Nuclear Engineering,;Vol. 2(2023)
Reviewartikel
P, Kumar, S. Holgersson, and C. Ekberg, “Cs, Ba, Co, and Eu sorption on biotite at pH 5-9 and varying ionic strength.”
Ämneskategorier
Fysikalisk kemi
Annan kemi
Geokemi
Styrkeområden
Energi
Materialvetenskap
Utgivare
Chalmers