A physicochemical model of thorium behaviour in the weathering profile

Abstract

Introduction: Author's and literature data on the standard Gibbs free energy for thorium ions and complexes in aqueous solution, as well as for two thorium minerals and 20 possible mineral phases are presented. Methodology: The behaviour of thorium in the process of weathering of phyllite-like shales was analysed using the program "Selektor” using computer physicochemical simulation. Results and discussion: The content of Th in shales was similar to the average content in the earth's crust and is equal to 10-3 wt.%. It was established that the content of thorium in the solution in the weathering -10profile was extremely low, its calculated concentration was less than 10 mol/l. Thorium was present almost exclusively in the form of Th(ОH)40 hydroxocomplexes, Th(ОH)5- and Th(OH)62-. During weathering, thorium accumulated and its content in bauxites averaged 40 g/t at a concentration coefficient of 4.16 [1], (3.4 according to [2]). Conclusions: Thorium accumulated during weathering processes and its concentration coefficient in bauxites was 4.16 [1] (3.4 according to [2]).