Proceedings of the Estonian Academy of Sciences, 2020
This study investigates the H 2 O-SrS (strontium sulphide) equilibrium system at [SrS] between 0.... more This study investigates the H 2 O-SrS (strontium sulphide) equilibrium system at [SrS] between 0.125 and 88.064 mM (mmol•L −1) in a closed oxygenfree test system at 25 ºC (the measured system's pH being in the range of 10.0-13.1). The distribution of ions and molecules in this system is described in a structural scheme. A proton transfer model was developed to calculate the pH, concentrations of formed ions and molecules in the system by using an iteration method. In the formation of the basic equilibrium system of H 2 O-SrS, the dissociation of SrS in aqueous media causes the release of the S 2− ions that will accept a certain quantity of protons (Δ[H + ] S 2-), originating from the reversible dissociation of water (Δ[H + ] H 2 O). In the final closed system of H 2 O-SrS, after adding larger amounts (≥10 g•L −1) of salt into MilliQ water, strontium hydroxide was formed as a precipitate. Proton transfer parameters, pH, and equilibrium concentrations of ions and molecules in the liquid phase were calculated and experimentally validated.
Surfactants are applied as emulsifiers or solubilizers by treatment of polluted soil. Theproblem ... more Surfactants are applied as emulsifiers or solubilizers by treatment of polluted soil. Theproblem of secondary pollution has arisen as result of the surfactant-enhanced remediation ofa polluted soil contaminated with hydrophobic organic compounds. Several studies haveshown that the surfactants are biodegradable in aerobic conditions and the biodegradabilitydepended on the chemical properties and concentration of surfactant. A study of the leachingof surfactants from the soil is important, as it is difficult to identify the reason for thereduction of concentration of pollutants in the soil: is it degradation or leaching? Theexperiments were carried out with a fine sandy soil in column tests and CaCO3 was added toincrease soil pH. The soil was treated twice with the bioremediation agent SR-100. The soilpH, the concentrations of anionic surfactant and petroleum hydrocarbons at the differentdepths of soil were determined. The microbial activity of soil fractions was evaluated byrespirome...
Proceedings of the Estonian Academy of Sciences, 2018
Variation in the concentration of dissolved carbon dioxide [CO 2 ] W causes changes in the solubi... more Variation in the concentration of dissolved carbon dioxide [CO 2 ] W causes changes in the solubility of limestone and in the pH of an equilibrium system. An elevation of the pH will shift the equilibrium of the reversible reaction NH 4 ⇌ NH 3 + H + towards the formation of free ammonia (NH 3). This results in the inhibition of the activity of microorganisms that perform the biological waste-and reject-water treatment. The model of the system H 2 O-(CO 2) W −CaCO 3 was upgraded on the basis of proton transfer principles and taken as the basis for modelling the closed system H 2 O-(CO 2) W-CaCO 3-NH 4 Cl. The distribution of ions and molecules in the closed system H 2 O-(CO 2) W-CaCO 3-NH X is described in terms of a structural scheme. A novel proton transfer model was developed to calculate the pH, concentrations of the formed ions and molecules, and proton transfer parameters of the closed equilibrium system using an iteration method. In the formation of the equilibrium system H 2 O-(CO 2) W −CaCO 3 , as a result of the dissolution of CaCO 3 , the CO 2 3 ions are released and these will accept a certain quantity of protons ( 2 3). The developed models were experimentally validated.
The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilib... more The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilibrium state after the dissolution of strontium sulfide in distilled water at 25 °C. The solubility of SrS was experimentally measured at a salt concentration range of 0.125–2.924 mM, and the determined pH was at a range of 10.0–11.6. The concentrations of different sulfide forms were determined spectrometrically, potentiometrically
CaS formed during the retorting process of oil shale has a hazardous influence on surface water q... more CaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur due to the CaS component. A theoretical model describing the behavior of solid calcium sulfide in contact with water was developed. The model was consistent with the measurements showing change in dissolution behavior when solid CaS remained in the solution. Experimental measurements of pH and concentrations of ions were carried out in oxygen‐free water at 25°C using CaS concentrations from 24.2–131.5 mg·L−1 (0.335–1.823 mmol/L). Analysis of pH and concentrations of ions in the solution and calculations by the developed model showed that the solubility of CaS was estimated as 125.0 mg·L−1 (1.733 mmol/L), and therefore the solubility product of CaS is 3.41×10−10 (mo·L−1)2 at a temperature of 25°C.
Proceedings of the Estonian Academy of Sciences, 2020
This study investigates the H 2 O-SrS (strontium sulphide) equilibrium system at [SrS] between 0.... more This study investigates the H 2 O-SrS (strontium sulphide) equilibrium system at [SrS] between 0.125 and 88.064 mM (mmol•L −1) in a closed oxygenfree test system at 25 ºC (the measured system's pH being in the range of 10.0-13.1). The distribution of ions and molecules in this system is described in a structural scheme. A proton transfer model was developed to calculate the pH, concentrations of formed ions and molecules in the system by using an iteration method. In the formation of the basic equilibrium system of H 2 O-SrS, the dissociation of SrS in aqueous media causes the release of the S 2− ions that will accept a certain quantity of protons (Δ[H + ] S 2-), originating from the reversible dissociation of water (Δ[H + ] H 2 O). In the final closed system of H 2 O-SrS, after adding larger amounts (≥10 g•L −1) of salt into MilliQ water, strontium hydroxide was formed as a precipitate. Proton transfer parameters, pH, and equilibrium concentrations of ions and molecules in the liquid phase were calculated and experimentally validated.
Surfactants are applied as emulsifiers or solubilizers by treatment of polluted soil. Theproblem ... more Surfactants are applied as emulsifiers or solubilizers by treatment of polluted soil. Theproblem of secondary pollution has arisen as result of the surfactant-enhanced remediation ofa polluted soil contaminated with hydrophobic organic compounds. Several studies haveshown that the surfactants are biodegradable in aerobic conditions and the biodegradabilitydepended on the chemical properties and concentration of surfactant. A study of the leachingof surfactants from the soil is important, as it is difficult to identify the reason for thereduction of concentration of pollutants in the soil: is it degradation or leaching? Theexperiments were carried out with a fine sandy soil in column tests and CaCO3 was added toincrease soil pH. The soil was treated twice with the bioremediation agent SR-100. The soilpH, the concentrations of anionic surfactant and petroleum hydrocarbons at the differentdepths of soil were determined. The microbial activity of soil fractions was evaluated byrespirome...
Proceedings of the Estonian Academy of Sciences, 2018
Variation in the concentration of dissolved carbon dioxide [CO 2 ] W causes changes in the solubi... more Variation in the concentration of dissolved carbon dioxide [CO 2 ] W causes changes in the solubility of limestone and in the pH of an equilibrium system. An elevation of the pH will shift the equilibrium of the reversible reaction NH 4 ⇌ NH 3 + H + towards the formation of free ammonia (NH 3). This results in the inhibition of the activity of microorganisms that perform the biological waste-and reject-water treatment. The model of the system H 2 O-(CO 2) W −CaCO 3 was upgraded on the basis of proton transfer principles and taken as the basis for modelling the closed system H 2 O-(CO 2) W-CaCO 3-NH 4 Cl. The distribution of ions and molecules in the closed system H 2 O-(CO 2) W-CaCO 3-NH X is described in terms of a structural scheme. A novel proton transfer model was developed to calculate the pH, concentrations of the formed ions and molecules, and proton transfer parameters of the closed equilibrium system using an iteration method. In the formation of the equilibrium system H 2 O-(CO 2) W −CaCO 3 , as a result of the dissolution of CaCO 3 , the CO 2 3 ions are released and these will accept a certain quantity of protons ( 2 3). The developed models were experimentally validated.
The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilib... more The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilibrium state after the dissolution of strontium sulfide in distilled water at 25 °C. The solubility of SrS was experimentally measured at a salt concentration range of 0.125–2.924 mM, and the determined pH was at a range of 10.0–11.6. The concentrations of different sulfide forms were determined spectrometrically, potentiometrically
CaS formed during the retorting process of oil shale has a hazardous influence on surface water q... more CaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur due to the CaS component. A theoretical model describing the behavior of solid calcium sulfide in contact with water was developed. The model was consistent with the measurements showing change in dissolution behavior when solid CaS remained in the solution. Experimental measurements of pH and concentrations of ions were carried out in oxygen‐free water at 25°C using CaS concentrations from 24.2–131.5 mg·L−1 (0.335–1.823 mmol/L). Analysis of pH and concentrations of ions in the solution and calculations by the developed model showed that the solubility of CaS was estimated as 125.0 mg·L−1 (1.733 mmol/L), and therefore the solubility product of CaS is 3.41×10−10 (mo·L−1)2 at a temperature of 25°C.
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