• Current Research on Agriculture and Life Sciences
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• v.6
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• pp.93-97
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• 1988

The physico-chemical properties of clay minerals(Kaolinite, Montmorillonite) and the competitive adsorption of various cations in them were investigated as a basic research for the development of clean and hygienic water from hard and contaminated water. The cation adsorption forces of various cations in two clay minerals were high in the order of $Ca^{{+}{+}}$ > $Mg^{{+}{+}}$ > $K^+$ > $Na^+$, and the orders of cation selectivity coefficients(K) in Montmorillonite, calculated by Kerr's equation, were $^KCa^{{+}{+}}/K$ > $^KMg^{{+}{+}}/K$, $^KCa^{{+}{+}}/Mg$ > $^KK^+/Mg$. The amount of adsorbed cations was most high in Na-saturated Montmorillonite among several samples. So, in order to more effectively remove various divalent cations in hard and contaminated water, Na-saturated Montmorillonite is most desirable.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.474-479
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• 2012

Possibility of the selective removal of $Ca^{2+}$ ions from a mixed solution of $Na^{+}$ and $Ca^{2+}$ ions using membrane capacitive deionization (MCDI) was investigated. Adsorption equilibrium experiments were conducted to determine the selectivity of the CMX cation-exchange membrane toward $Ca^{2+}$ ions. In addition, desalination experiments for a mixed solution (5 meq/L NaCl + 2 meq/L $CaCl_{2}$) were performed using an MCDI cell. The adsorption equilibrium of CMX membrane showed that the equivalent fraction of $Ca^{2+}$ ions in the solution and the CMX membrane were 28.6 and 87.2%, respectively, which indicates the CMX membrane's high selectivity toward $Ca^{2+}$ ions. Desalination experiments were performed by applying a constant current to the MCDI cell until the cell potential reached 1.0 V. The amount of ions adsorbed did not significantly change as the applied current was changed. However, the equivalent fractions of $Ca^{2+}$ ions among the adsorbed ions were inversely proportional to the applied currents: 81.4, 78.4, 77.0, and 74.5% at 200, 300, 500, and $700\;A/m^{2}$ of applied current density, respectively. This result is attributed to the increased fraction of $Ca^{2+}$ ions adsorbed by the CMX membrane at lower applied current densities.

• Clean Technology
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• v.24 no.1
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• pp.41-49
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• 2018

Y zeolites with different extra-framework cations, such as $Na^+$, $N^+$, $Ca^{2+}$, and $Cu^{2+}$, with different charge and ionic radius have been investigated to greatly enhance a working capacity (W) of $CO_2$ adsorption at $25^{\circ}C$ and a $CO_2/CO$ selectivity factor (S). A sample of NaY with a very small amount of 0.012% $Ca^{2+}$ was fully reversible for seven times repeated $CO_2$ adsorption/desorption cycles, thereby forming no surface carbonates unlikely earlier reports. Although at pressures above 4 bar, 2.00% CaY, 1.60% CuY and 1.87% LiY all showed a $CO_2$ adsorption very similar to that measured for NaY, they gave a significant decrease in the adsorption at lower pressures, depending on the metal ion. At 0.5 ~ 2.5 bar, the extent of $CO_2$ adsorption was in the order NaY > 1.60% CuY > 2.00% CaY > 1.87% LiY. All the $Na^+-based$ metals-exchanged zeolites have a FAU (faujasite) framework and a Si/Al value near 2.6; thus, there is no discernible difference in the framework topology, framework chemical compositions, effective aperture size, and channel structure between the zeolite samples. Therefore, the distinctive behavior in the adsorption of $CO_2$ with a character as a weak Lewis acid is associated with the site basicity of the zeolites, and the interaction potentials of the cations. Different trend was shown for a CO adsorption due to weaker quadrupole interactions. Adsorption of $CO_2$ and CO on samples of CaY with 0.012 to 5.23% Ca disclosed a significant dependence on the Ca loading. The $CO_2$ adsorption increased when the cation exists up to ca. 0.05%, while it decreased at higher Ca amounts. However, values for both W and S could greatly increase as the bare zeolite is enriched by $Ca^{2+}$ ions. The 5.23% CaY had $W=2.37mmol\;g^{-1}$ and S = 4.37, and the former value was comparable to a benchmark reported in the literature.

• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.59-71
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• 2016

To investigate the sorption characteristics of Cs, which is one of the major isotopes of nuclear waste, on natural zeolite chabazite, XRD, EPMA, EC, pH, and ICP analysis were performed to obtain the informations on chemical composition, cation exchange capacity, sorption kinetics and isotherm of chabazite as well as competitive adsorption with other cations ($Li^+$, $Na^+$, $K^+$, $Rb^+$, $Sr^{2+}$). The chabazite used in this experiment has chemical composition of $Ca_{1.15}Na_{0.99}K_{1.20}Mg_{0.01}Ba_{0.16}Al_{4.79}Si_{7.21}O_{24}$ and its Si/Al ratio and cation exchange capacity (CEC) were 1.50 and 238.1 meq/100 g, respectively. Using the adsorption data at different times and concentrations, pseudo-second order and Freundlich isotherm equation were the most adequate ones for kinetic and isotherm models, indicating that there are multi sorption layers with more than two layers, and the sorption capacity was estimated by the derived constant from those equations. We also observed that equivalent molar fractions of Cs exchanged in chabazite were different depending on the ionic species from competitive ion exchange experiment. The selectivity sequence of Cs in chabazite with other cations in solution was in the order of $Na^+$, $Li^+$, $Sr^{2+}$, $K^+$ and $Rb^+$ which seems to be related to the hydrated diameters of those caions. When the exchange equilibrium relationship of Cs with other cations were plotted by Kielland plot, $Sr^{2+}$ showed the highest selectivity followed by $Na^+$, $Li^+$, $K^+$, $Rb^+$ and Cs showed positive values with all cations. Equilibrium constants from Kielland plot, which can explain thermodynamics and reaction kinetics for ionic exchange condition, suggest that chabazite has a higher preference for Cs in pores when it exists with $Sr^{2+}$ in solution, which is supposed to be due to the different hydration diameters of cations. Our rsults show that the high selectivity of Cs on chabazite can be used for the selective exchange of Cs in the water contaminated by radioactive nuclei.

• Economic and Environmental Geology
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• v.28 no.3
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• pp.231-241
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• 1995

It is well known that hydroxyapatite [$Ca_{10}(PO_4)_6(OH)_2$] have an exchangeability for various heavy metal ions in aqueous solution. To evalute the feasibility of employing the synthetic hydroxyapatites as an eliminatable exchanger for environmentally noxious caions in waste water, the adsorption properties, the removal capacities and the selectivity of the apatites for various cations were investigated in more detailed. The heavy metal cations have been exchanged in calcium part of hydroxyapatite. The order of the degree of amount exchanged of the investigated cations is $Pb^{2+}>Cd^{2+}>Zn^{2+}>Ba^{2+}$. The molar ratios between released $Cd^{2+}$ ions and remeved divalent metal cations in the reacted solution with hydroxyapatite are roughly close to an integer 1.0, suggesting that an ion-exchange reaction could have played a major role in the removal of heavy metals rather then an adsorption effect. The exchangeability of the hydroxyapatite powder of Ca/P molar ratio 1.67, which have specipic surface area of $104.5m^2g^{-1}$, appeared to be better then $237.6{\mu}g$ per g for $Pb^{2+}$ ions. The removal capacity of the heavy metal ions varies directly as particle size of hydroxyapatites. All evidences obtained indicate that the synthesized hydroxyapatite powders by precipitation reaction method can be employed as an effective cation exchanger for eliminating noxious ions in waste water even in some improvemental.

• Membrane Journal
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• v.25 no.5
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• pp.431-439
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• 2015

The study was evaluated and compared to commercial heterogeneous membrane in order to make cation exchange membrane set up the optimal preparing condition. The research findings show that ion exchange resin was added more than 40 wt% in order to show chemical properties of HPVDF higher than commercial heterogeneous membrane. But ion exchange resin was added less than 40 wt% in order to show mechanical properties of HPVDF higher than commercial heterogeneous membrane. According to conditions above, Electrical resistance was $1.83{\Omega}{\cdot}cm^{-1}$, water uptake was 79%, ion exchange capacity was 1.60 meq/g, and burst strength was 0.97 MPa. Also The TDS remove efficiency was measured by approximately 40%.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.2
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• pp.117-124
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• 2023

X-ray diffraction analysis, X-ray fluorescence analysis, thermal differential and thermos gravimetric analysis, cation exchange capacity analysis, and Cesium (Cs), Strontium (Sr) adsorption experiments were performed to investigate the physical and chemical properties of natural zeolite from Guryongpo in Korea. As a result of X-ray diffraction analysis, minerals such as mordenite, heulandite, clinoptilolite, and illite are contained, and as a result of X-ray fluorescence analysis, elements such as SiO₂, Al₂O₃, CaO, K₂O, MgO, Fe₂O₃ and Na₂O are contained, and the cation exchange capacity was 148.6 meq/100 g. As a result of thermal differential and thermos gravimetric analysis, it was confirmed that the thermal stability was excellent up to 600 ℃. As a result of the adsorption equilibrium experiment over time, the equilibrium was reached within 30 min. for Cesium (Cs) and within 8 hr. for Strontium (Sr), and the adsorption rates of Cesium (Cs) and Strontium (Sr) were 80% and 18%, respectively. As a result of the single-component isothermal adsorption experiment, in conformed to the Langmuir model, and the maximum Cesium (Cs) adsorption amount was 131.5 mg/g, which was high, while the Strontium (Sr) maximum adsorption amount was 29.5 mg/g, which was low. In the case of the natural zeolite used in this study, the content of minerals including 8-rings such as clinoptilolite, heulandite, and mordenite is high, showing high selectivity for Cesium (Cs).

• Journal of Environmental Science International
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• v.18 no.6
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• pp.645-654
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• 2009

Lab-scale Electrodialysis(ED) system with different membranes combined with before or after pyroma process were carried out to remove nitrate from two pickling acid wastewater containing high concentrations of $NO_3\;^-$(${\approx}$150,000 mg/L) and F($({\approx}$ 160,000 mg/L) and some heavy metals(Fe, Ti, and Cr). The ED system before Pyroma process(Sample A) was not successful in $NO_3\;^-$ removal due to cation membrane fouling by the heavy metals, whereas, in the ED system after Pyroma process(Sample B), about 98% of nitrate was removed because of relatively low $NO_3\;^-$ concentration (about 30,000 mg/L) and no heavy metals. Mono-selective membranes(CIMS/ACS) in ED system have no selectivity for nitrate compared to divalent-selective membranes(CMX/AMX). The operation time for nitrate removal time decreased with increasing the applied voltage from 10V to 15V with no difference in the nitrate removal rate between both voltages. Nitrate adsorption of a strong-base anion exchange resin of $Cl\;^-$ type was also conducted. The Freundlich model($R^2$ > 0.996) was fitted better than Langmuir mode($R^2$ > 0.984) to the adsorption data. The maximum adsorption capacity ($Q^0$) was 492 mg/g for Sample A and 111 mg/g for Sample B due to the difference in initial nitrate concentrations between the two wastewater samples. In the regeneration of ion exchange resins, the nitrate removal rate in the pickling acid wastewater decreased as the adsorption step was repeated because certain amount of adsorbed $NO_3\;^-$ remained in the resins in spite of several desorption steps for regeneration. In conclusion, the optimum system configuration to treat pickling acid wastewater from stainless-steel industry is the multi-processes of the Pyroma-Electrodialysis-Ion exchange.