CARBONATE DISSOLUTION AND CO₂ RELEASE IN BENTONITES AT ELEVATED TEMPERATURES

Two series of experiments with four and 15 bentonites and two model clay porewaters with salinities of 19 g/l and 155 g/l reveal a CO₂ generation in 1:2 bentonite–porewater suspensions at 90 °C and 120 °C. Within three to 12 months, partial CO₂ pressures of up to 2 bar and CO₂ contents of ~ 31 to ~ 38 vol .% in the headspace of the batch vessels were observed which originated from the dissolution of carbonate minerals with a rate of 1.1 up to 2.1 % of bentonite mass per year. An only minor CO₂ release in control batches with calcite suspensions, an absence of a correlation between the initial carbonate con-tent and CO₂ release in bentonites, and a dependence of CO₂ release on both solution composition and bentonite identity suggest as a reason for these observations an under-lying carbonate dissolution reaction involving one or more non-carbonate bentonite com-ponents.

Key words: bentonite, calcite, gas generation, engineered barriers, geological repository.

Meleshyn A. Yu. Carbonate Dissolution and CO₂ Release in Bentonites at Elevated Temperatures. Radioactive Waste, 2019, no. 2 (7), pp. 65—75. DOI: 10.25283/2587-9707-2019-2-65-75. (In Russian).