Investigating the effect of contact time and liquid-to-solid ratio on bisulphide sorption onto bentonite through laboratory batch experiments
Sifat Azad Papry, Tarek L. Rashwan, Pulin Mondal, Magdalena Krol, Mehran Behazin, Peter G. Keech
In the proceedings of: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNCABSTRACT: The Nuclear Waste Management Organization (NWMO) has designed a deep geological repository (DGR) to safely house Canada's used nuclear fuel around 500 m deep in a stable rock formation. Within a DGR, an engineered barrier system (EBS) will be used to safely contain and isolate the used fuel containers (UFCs). The EBS includes the copper coated UFCs surrounded by highly compacted bentonite. One key aspect regarding the long-term performance of EBS is the corrosion of UFC, which could occur due to bisulphide (HS-) produced by sulphate reducing bacteria near the rock-bentonite interface. If produced, HS- may diffuse through the bentonite buffer and react with the copper surface of the UFC. Although sorption of HS- onto bentonite may limit the flux of HS-, few studies have systematically investigated this phenomenon in the hydrogeochemical context of a DGR. This study aims to address this knowledge gap by investigating the sorption of HS- onto bentonite through batch experiments varying contact time (1 and 24 hours) and liquid to solid (L:S) ratios (50, 100, and 200). Experiments were performed using MX-80 bentonite, with all other experimental conditions remaining constant, e.g., pH (at 9), temperature (at 22 +- 2degC), and HS- initial concentration (1.0 mg/L). The results show that increasing L:S ratio, decreases HS- sorption efficiency due to the reduction of available sorption sites, whereas the amount of HS- sorbed per unit weight of bentonite increased from 33-34 to 79-90 mg/g. In addition, no significant variation in sorption was observed with an increase in contact time, which implies that most of the sorption occurred within the first hour of contact with bentonite. These findings will be used to investigate the sorption phenomenon of HS- onto bentonite under various DGR conditions and inform a reactive transport model that will be used to assess the long-term performance of the EBS.
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Papry, Sifat Azad, Rashwan, Tarek L., Mondal, Pulin, Krol, Magdalena, Behazin, Mehran, Keech, Peter G. (2021) Investigating the effect of contact time and liquid-to-solid ratio on bisulphide sorption onto bentonite through laboratory batch experiments in GEO2021. Ottawa, Ontario: Canadian Geotechnical Society.
@article{Papry_GEO2021_259,
author = Sifat Azad Papry, Tarek L. Rashwan, Pulin Mondal, Magdalena Krol, Mehran Behazin, Peter G. Keech,
title = Investigating the effect of contact time and liquid-to-solid ratio on bisulphide sorption onto bentonite through laboratory batch experiments ,
year = 2021
}
title = Investigating the effect of contact time and liquid-to-solid ratio on bisulphide sorption onto bentonite through laboratory batch experiments ,
year = 2021
}