Abstract
This research was conducted with the use of the DSC method; it involved the examination of the unfrozen water content in two model (source) calcium bentonites (≥75% smectite), after one to three freeze-thaw cycles in the natural state, as well as after the ion exchange for a potentially toxic element (Cu2+). The freeze-thaw cycles do not affect the unfrozen water content at a given negative temperature in a statistically significant manner. However, a statistically significant influence of temperature, the initial mass of the water, and the clay type on the change of the unfrozen water content was found. Moreover, the empirical models of predicting the unfrozen water in the bentonite after the exchange for Cu2+ ion were created, for which the parameter was the mass of the water and the mass of the dry soil, at the temperature of −2 °C.
Highlights
Unfrozen Water Content of CalciumIn the case of the clay-water system, part of the water remains in a liquid state belowThe fraction of the above-mentioned water is called the unfrozen water, while its amount below the freezing point gradually decreases as the temperature drops
The same tendency was observed by the authors during the examination of the bentonite contaminated with copper ions using the 1 H NMR method [19]
This may be the effect of a decrease in the specific surface area that occurred in the clays as a result of the introduction of copper ions into their structure (Table 2)
Summary
Unfrozen Water Content of CalciumIn the case of the clay-water system, part of the water remains in a liquid state belowThe fraction of the above-mentioned water is called the unfrozen water, while its amount below the freezing point gradually decreases as the temperature drops. The authors put an emphasis on the issue that this knowledge is especially important in the case of bentonites, which are used as geological barriers in dangerous waste landfills and may be impacted by the potentially toxic metal ions [10]. Knowledge of this water fraction may contribute to the undertaking of appropriate actions aimed at preventing the clay contamination, predicting its effects and possibly selecting a method for Bentonites Modified by Copper Ions
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