The unfrozen water content in frozen soils strongly infl uences heat and mass transport processes. Despite massive research work, the actual implica ons of the freeze-thaw process on unfrozen water s ll remain unknown. The main objec ve of this study was to examine the hypothe cal eff ect of a number of previous freeze-thaw cycles on the unfrozen water content during the current cycle. Several bentonites (Stx-1b from Wyoming, SWy-2 from Texas, as well as Ca, Na, and K forms of bentonite from Chmielnik) with diff erent water contents were subjected to repeated freezing to −90°C and thawing at 20°C in a diff eren al scanning calorimeter (DSC). The total number of cycles was fi ve. The unfrozen water contents were determined on warming during each cycle by the use of the stochas c deconvolu on of the DSC signal. According to the ANOVA results, the freeze-thaw eff ect on the unfrozen water content w u in the bentonites was not sta s cally signifi cant. A clear pa ern of altera ons of w u with the number of consecu ve cycles could be dis nguished, however, depending on the major exchangeable ca on. The kind of exchangeable ca on played a predominant role in the temperature dependence of the unfrozen water content. The specifi c surface area strongly aff ected the unfrozen water content at lower temperatures, i.e., at −5°C and below. Closer to 0°C, the eff ect of the specifi c surface became absolutely insignifi cant, and the clay frac on content determined by the laser diff rac on method proved to be the soil property best correla ng with the unfrozen water content at −1°C.Abbrevia ons: DSC, diff eren al scanning calorimeter.The frost phenomena in soils play an important role in many types of problems in such varied fi elds as civil engineering, road geotechnics, agriculture, and meteorology. Many aspects of "frost geotechnics" have been being analyzed by many researchers for >100 yr. Th ese include a general physics of the process, i.e., the freezing point depression and the water remaining unfrozen under the freezing point, frost heaving and the associated phenomena of mass transport, the mechanical properties of frozen soil, and many others. Th e cycling of freezing and thawing can be seen in this context in two ways. First, the freeze-thaw cycles generate their own specifi c phenomena, such as the resulting alteration of the soil structure and microstructure. Second, the history of previous cyclic freezing and thawing may aff ect the frost phenomena and soil properties as observed in a current freezing cycle or in the thawed state. Hence, an experimental design can be planned with the object to determine and, in some cases, explain the extent and kind of possible impact.Th e alteration of the soil microstructure and fabric due to cyclic freezing and thawing seems to have been confi rmed by many researchers by the use of scanning electron microscopy. Kujala and Laurinen (1989) observed that as a result of repeated freezing and thawing, the plate-like clay particles of their soil samples became aggregated in a rand...
The aim of this study was to determine the influence of potentially toxic metals, such as Cu 2þ and Zn 2þ ions, on the microstructural parameters of bentonites and their hydraulic conductivity (K), calculated based on the empirical formulas for clays according to Hazen-Tkaczukowa (formula 1 based on granulometric parameters) and Kozłowski et al., (2011) (formula 2 based on microstructural parameters). Metal ions influence the microstructure changes of bentonites, which can lead to changes in the geotechnical parameters that are used in empirical K formulas. The research was carried out on model clays (SWy-3, Stx-1b and Slovak bentonite), which were modified by introducing Cu 2þ or Zn 2þ ions into the structure. A significant dependence was observed between an increase in the Cu 2þ ion content in clay and an increase in the pore area. Therefore, the value of the hydraulic conductivity was estimated with the use of formula 2, which proved to be a useful tool for determining hydraulic conductivity in the case of bentonites contaminated with Cu 2þ ions. In contrast, the effect of Zn 2þ ions on the granulometric parameters was significant, and formula 1 proved to be useful tool for determining hydraulic conductivity in the case of bentonites contaminated with Zn 2þ ions. The results showed that the behavior of bentonites saturated with Cu 2þ and Zn 2þ ions differed. Therefore, the authors believe that the empirical formulas of the hydraulic conductivity of the clays saturated with potentially toxic metals should be based on the selected clay parameters dependent upon the nature of the ion.
This paper discusses an environmental criterion rarely addressed in the literature for the selection of salt hydrates for use in photovoltaic installations as Phase change materials. The aim of the paper is to assess the possibility of utilization of used salt hydrates from photovoltaic installations according to current Polish legal requirements concerning the environment. The properties of the composition components of hydrated salts were discussed in terms of their safety for the environment before and after the period of exploitation in photovoltaic panels. A method of dealing with used salt hydrates was proposed and a waste code was assigned. It has been established that spent salt hydrates will be allowed to be collected in no-outflow tanks and accepted at liquid waste collection points, which operate at water supply and sewerage companies, and the load of permissible pollutants should not exceed the value for industrial sewage.
The purpose of this study was to determine the effect of copper or zinc ions, absorbed by soil on its physical and physicochemical properties. The change in these properties may reduce the soil usefulness as a mineral protective barrier, for example, on hazardous waste landfills. Parameters such as granulometric composition, effective particle size d 10 , empirical hydraulic conductivity, Atterberg limits, colloidal activity, specific surface area, sorption moisture content, and montmorillonite content were determined. The tests were carried out on model Na þ or Ca 2þ samples of American bentonites (SWy-3, Stx-1b) and Slovak bentonite from Jel sový potok (BSvk), subjected to ion exchange for Cu 2þ or Zn 2þ ion. The content of elements was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Regression analysis showed a significant effect of Zn 2þ ions on the reduction of sorption moisture content w 95 and the increase in the hydraulic conductivity. Nearly complete negative correlation was obtained between the Cu 2þ ion content and the specific surface area, sorption moisture content w 50 , and montmorillonite content (R ¼-0.99). It was observed that the significance of the influence of Cu 2þ and Zn 2þ ions on specific clay properties differed, which indicates different behavior of these metals in the clay-water system. The different nature of clays contaminated with Cu 2þ and Zn 2þ ions justifies the need to continue research on other potentially toxic metals and to further search for prediction equations of the cohesive soil hydraulic conductivity based on soil parameters that are most frequently modified as a result of their impact.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.