• Analytical Science and Technology
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• v.13 no.4
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• pp.433-439
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• 2000

Adsorption behaviors of Ni(II) ions were investigated using amorphous alumina as adsorbent. In the adsorption kinetic study, it was observed that Ni(II) ions were bound to the alumina surface in two adsorption stages, the rapid and slow adsorption stages. The rapid adsorption proceeded within 1 hr, thereafter the slow adsorption occurred. The results of adsorption isotherm experiments showed that the Ni(II) adsorption obeyed the Langmuir-Freundlich isotherm, and that the adsorption enhanced with increasing pH. The change in ionic strength did not exhibit a conspicuous trend in Ni(II) adsorption, thereby suggesting that the adsorption occurs through surface complexation rather than electrostatic interactions. The amounts of adsorption were measured with varying pH at three different Ni(II) concentrations under the condition of constant ionic strength, showing that with increasing Ni(II) concentration, the percentage of adsorption decreased and the adsorption edge was shifted to a higher pH value.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.322-324
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• 2003

이온교환은 액체상에 존재하는 이온과 고체상에 존재하는 이온이 당량적으로 치환되는 것으로 정의하며, 치환되는 정도는 일반적으로 전하의 크기와 이온이 수화반경에 따라 달라진다. 지금까지의 이온교환 반응에 대한 모델링 연구는 실험식, 질량작용식, 열역학식, 전기이중층이론, 표면착화모델 등을 이용하여 2 성분에 대하여 다양한 시도를 하였다. 본 연구에서는 2, 3, 4성분에 대해 질량작용법칙과 전기이중층이론을 조합한 표면착화모델과 질량작용법칙을 이용한 모델을 수행하였다. 그 결과 표면착화모델이 질량작용법칙을 이용한 것보다 실험치와 일치함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.324-327
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• 1998

The mechanisms of Cu2+ adsorption onto goethite, hematite and kaolinite are different. Goethite and hematite showed a similar adsorption behavior (ionic-strength independent), but kaolinite gave somewhat different result (ionic-strength dependent). These experimenal results were successfully simulated using a surface complexation model, TLM, which defines the inner- or outer-sphere complex. The chemical nature of Cu2+ adsorption onto kaolinite was qualitatively identified by EPR spectroscopy.

• Journal of the Mineralogical Society of Korea
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• v.17 no.2
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• pp.157-168
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• 2004

The surface chemical properties of aqueous kaolinite and halloysite were studied using a potentiometric titration experiment and a computer program FITEQL3.2. Among the surface complexation models a constant capacitance model was selected for this study. The 2 sites - 3 p $K_{a}$ s model, in which the surfaces were assumed to have tetrahedral and octahedral sites, was reasonable for the description of the experimental data. The surface charges of both minerals were negative above pH of 4. The higher the pH, the lower the proton surface charge densities of both minerals. The ≡ $SiO^{[-10]}$ site played an important role in cation adsorption in acid and neutral pH range; whereas the ≡ Al $O^{[-10]}$ site was in an alkaline pH range. The optimized intrinsic constants of kaolinite, p $K_{a2(Si)}$$^{int}$, p $K_{al(Al)}$$^{int}$ and p $K_{a2(Al)}$$^{int}$ were 4.436, 4.564, and 8.461 respectively, and those of halloysite were 7.852, 3.885, and 7.084, respectively. The total Si and Al surface sites concentrations of kaolinite were 0.215 and 0.148 mM, and those of halloysite were 0.357 and 0.246 mM. The ratio of Si and Al surface site densities ([≡SiOH]:[≡AlOH]) of both minerals was 1 : 0.69. The total surface site density of kaolinite, 3.774 sites/n $m^2$, was 1.6 times larger than that of halloysite, 2.292 sites/n $m^2$./TEX>.

• Journal of Environmental Science International
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• v.8 no.2
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• pp.205-209
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• 1999

Iron hydroxides are good adsorbents for uncomplexed metals, some metal-ligand complexes and many metal oxyanions. However, their adsorption properties of these precipitations are not fully exploited in wastewater treatment operations because of difficulties associated with their separation from the aqueous phase. This study describes experiments in which iron hydroxides were coated onto the surface of ordinary adsorbents(Sea sand) that are very resistant to acids, The coated adsorbents were used in adsorption of oxyanionic metals. The process was successful in removing some anions such as $SeO_3(-II)$ over a wide range of metal concentrations and sorption of oxyanionic metals increased with decreasing pH. Formation of two surface complexes for oxyanionic metals adsorption on iron hydroxides comprise (1) complexation of the free anion by a positively charged surface site, and (2) protonation of the adsorbed anion (or alternatively adsorption of a protonated form from solution) The coated adsorbents are inexpensive to prepare and could serve as the basis of a useful oxyanionic metal removal.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.12 no.1
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• pp.17-33
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• 1986

The interfacial Properties of ferrosoferric oxide suspended in aqueous KNO3 solution are investigated by studying the zeta potentials and surface charge densities at $25^{\circ}C$. The zeta potentials are obtained by measuring the electrophoretic mobility and the surface charge densities by potentiometric titrations in the aqueous KNO3 solutions of different concentrations from 10-3 to 10-1M. The data are interpreted by the surface dissociation and complexation model of Davis, et als. and the modified model.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.2
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• pp.151-160
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• 2022

The sorption of Eu on MX-80 bentonite in Na-Ca-Cl solutions is investigated at a molal proton concentration (pH_m) range of 3 to 10 and an ionic strength (I) range of 0.1 to 6 m (mol·kgw^-1). The sorption equilibrium of Eu on MX-80 is achieved within 14 to 21 d at I = 0.1 and 6 m. The sorption distribution coefficient (K_d) values of Eu for MX-80 increase as pH_m increases from 3 to 6 for all I values, and they are independent of pH_m between 8 and 10 at I ≥ 0.5 m. Meanwhile, at I = 0.1 m, the K_d value at pH_m = 10 is slightly lower than those at pH_m = 8 and 9. The K_d values are not affected by the I values between 0.5 m and 6 m, whereas the K_d value at I = 0.1 m is greater than those at I ≥ 0.5 m, except at pH_m = 10. A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model is applied to the Eu sorption data for I ≤ 4 m, and the equilibrium constants of the sorption reactions are estimated.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1616-1622
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• 2022

Selenium has been identified as an element of interest for the safety assessment of a deep geological repository (DGR) for used nuclear fuel. In Canada, groundwaters at DGR depths in sedimentary rocks have been observed to have a high ionic strength. This paper examines the sorption behavior of Se(-II) onto illite, MX-80 bentonite, Queenston shale, and argillaceous limestone in Na-Ca-Cl solutions of varying ionic strength (0.1-6 mol/kgw (m)) and across a pH range of 4-9. Little ionic strength dependence for Se(-II) sorption onto all solids was observed except that sorption at high ionic strength (6 m) was generally slightly lower than sorption at low ionic strength (0.1 m). Illite and MX-80 exhibited the expected results for anion sorption, while shale and limestone exhibited more constant sorption across the pH range tested. A non-electrostatic surface complexation model successfully predicted sorption of Se(-II) onto illite and MX-80 using the formation of an inner-sphere surface complex and an outer-sphere surface complex. Optimized values for the formation reactions of these surface species were proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.560-567
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• 2006

Although various conjectures have been proposed to explain abnormal increase in thermal conductivity of nanofluids, the detailed mechanism could not be understood and explained yet. The main reason is primarily due to the lack of knowledge on the most fundamental factor governing the mechanisms such as Brownian motion, liquid layering, phonon transport, surface chemical effects and agglomeration. By applying surface complexation model for the measurement data of hydrodynamic size, zeta potential, and thermal conductivity, we have shown that sulfate charge state is mainly responsible for the increase in the present condition and may be the factor incorporating all the mechanisms as well. Moreover, we propose a new model including concepts of fractal and interfacial layer. The properties such as thickness and thermal conductivity of the layer are estimated from the surface charge states and the concept of electrical double layer. With this, we could demonstrate the pH dependences of the layer properties and eventually of the effective thermal conductivity of the nanofluid.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.166-171
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• 2007

The adsorption behavior of $Pb^{2+}$ was compared between calcium alginate beads and capsules, which have different structures of alginate-gel core beads and liquid core alginate-membrane capsules, respectively. In terms of adsorption kinetics and isotherms, adsorption characteristics depending on pH and hardening time were compared for both adsorbents and also released calcium ion during the adsorption process was monitored. The adsorption of $Pb^{2+}$ on both adsorbents was caused by surface complexation and ion exchange mechanisms, both of which have similar effects on adsorption process regardless of the amount of adsorbed $Pb^{2+}$. The dependence of $Pb^{2+}$ adsorption upon pH was also similar for both adsorbents indicating the existence of similar functional groups on the surface of adsorbents. However, a different $Pb^{2+}$ adsorption behavior was observed considering the adsorption kinetics. The adsorption kinetic of $Pb^{2+}$ on alginate beads was slower than on alginate capsules and the maximum adsorption loading ($Q_{max}$) onto alginate beads was also less than onto alginate capsules by 49%. This drawback of alginate beads compared to capsules were ascribed to a diffusion limitation due to solid gel-core structure of alginate beads.