• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.13-19
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• 1998

This study was carried out to investigate characteristics and Pb(II) removal effect of natural Muan, Seosan, Kangjin clays in the batch mode test to develope the low-priced treatment agent of wastewater which contain heavy metals in order structural, optical properties and chemical compositions of natural clays from domestic have been investigated to have high specific surface area and have minerals such as $SiO_2$ and $Al_2O_3$. As a result, removal effects of Pb(II) ions on clays were reached at equilibrium in aqueous solutions by stirring about 20minutes. The removal effect of Pb(II) ions was best for Seosan clay than Muan or Kangjin clays in terms of fixed time. The results show the possibility of continuous treatment system of wastewater which contain heavy metals by using natural clays from domestic.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1179-1180
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• 2005

To immobilize the pollutants from wastewater in situ, two phosphatic clays collected from different areas in Egypt (eastern and western Sebaia, Aswan-Isna, Upper Egypt) used to remove contaminant ions from industrial wastewater. Obtained results confirmed the strong relationship between phosphatic clay and Pb elimination from wastewater. The sensitivity classification of phosphatic clay toward ions retained as described in three categories: highly sensitive to retain Pb , Al and Cr ; moderately sensitive for Mn; and weakly sensitive for Band Zn. Data suggested that large fraction of Pb removed by phosphatic clays stayed intact under a wide variation in extracting solution pH (3-11). In situ immobilization is considered a promising technique that has the potential to remove contaminant ions from wastewater. Two important factors need to be considered when applying this technique: The first, is the clay must be effective and selective under different composition of wastewater. The second, is the immobilized ions should be stable and non-leacheable under varying water conditions. Phosphatic clays with $Pb^{2+}$ were suitable to achieve these two factors. Possible mechanism for removal $Pb^{2+}$ by phosphatic clays is the formation of fluoropyromorphite through the dissolution of fluoro and hydroxyl apatite by its precipitation from solution, beside, Pb complexation at phosphatic clay surface at P-OH sites.

• Geomechanics and Engineering
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• v.10 no.6
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• pp.827-836
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• 2016

The rate of softening is an important factor to determine whether the failure occurs along localized shear band or in a more diffused manner. In this paper, strength loss and softening rate effect depending on sensitivity are investigated for weakly cemented clays, for both artificially cemented high plasticity San Francisco Bay Mud and low plasticity Yolo Loam. Destructuration and softening behavior for weakly cemented sensitive clays are demonstrated and discussed through multiple vane shear tests. Artificial sensitive clays are prepared in the laboratory for physical modeling or constitutive modeling using a small amount of cement (2 to 5%) with controlled initial water content and curing period. Through test results, shear band thickness is theoretically computed and the rate of softening is represented as a newly introduced parameter, ${\omega}_{80%}$. Consequently, it is found that the softening rate increases with sensitivity for weakly cemented sensitive clays. Increased softening rate represents faster strength loss to residual state and faster minimizing of shear band thickness. Uncemented clay has very low softening rate to 80% strength drop. Also, it is found that higher brittleness index ($I_b$) relatively shows faster softening rate. The result would be beneficial to study of physical modeling for sensitive clays in that artificially constructed high sensitivity (up to $S_t=23$) clay exhibits faster strain softening, which results in localized shear band failure once it is remolded.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.1-20
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• 2023

To predict the consolidation behavior of dredged and reclaimed marine clays exhibiting consolidation settlement with large strains, the finite strain consolidation theory must be used. However, challenges in appropriately applying the theory and determining input parameters make design and analysis studies difficult. To address these challenges, design charts for predicting the consolidation settlement of reclaimed marine clays are developed by a numerical approach based on the finite strain consolidation theory. To prepare the design charts, a sensitivity analysis of parameters is performed, and influencing parameters, such as initial void ratio and initial height, as well as the non-linear constitutive void ratio-effective stresspermeability relation, are confirmed. Six representative Korean marine clays obtained from different locations with different liquid limits are used. The design charts for estimating the consolidation times corresponding to various degrees of consolidation are proposed for each of the six representative clays. The consolidation settlements predicted from the design charts are compared to those in previous studies and at an actual construction site and are found to agree well with them. The proposed design charts can therefore be used to solve problems related to the consolidation of reclaimed marine clays having large strains.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.401-414
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• 2023

Organic clays are ideal habitat for flora and fauna. From a geotechnical perspective, organic clays are soft, weak, variable, heterogeneous and flocculated. Portland cement is a universally common stabiliser. However, some organic acids in soil inhibit full hydration and expose cementation products to rapid dissolution. This paper investigates scopes for use of C₃S cement to enable durable cementation. Prospects of using PP fibre alongside with C₃S cement, scopes for partial replacement of C₃S cement with a plant-based nanosilica and evolution of binders are then investigated. Binding mixtures here mimic the natural functions of rhizoliths, amorphous phases, and calcites. Testing sample population include natural and fibre-reinforced clays, compact mixes of clay - C₃S cement, clay - nanobiosilica, and clay, C₃S cement and nanobiosilica. Benefits and constraints of C₃S cement and fibres for retaining the naturally flocculated structure of organic clays are discussed. Nanobiosilica provides an opportunity to cut the C₃S content, and to transition of highly compressive organic clays into an engineered, open-structured medium with >0.5 MPa compressive strength across the strains spanning from peak to 1.5-times peak.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.938-946
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• 2008

This study is on sealing leakage holes where are in landfills to make clay cakes with clay particles, which have a negative surface charge using the method of electrophoresis. Generally, electrophoresis is the motion of charged particles in a colloid under the influence of an electric field; particles with a positive charge go to the cathode and negative to the anode. In this study in order to develop the prevention system of leakages of the leachate in landfills, one-dimensional electrophoresis tests were conducted for determining the properties of the motion of the electrophoresis and cutoff using the method of electrophoresis depending on various the effect factors such as types of clays, concentrations of the clays, and applied electric field. In case of the experiments of determining the optimum clays, Na and Ca-Bentonite, Na and Ca-Montmorillonite, which have greater zeta-potential, cation, exchange capacity as well as ability of cutoff, and Micro-cement inducing cementation were chosen and then the effect of those clays was investigated. Moreover, the properties of the motion and settling of the clays were investigated following electric field varied from 0 to 1V/cm at different concentration of the clays in order to determine both the properties of the motion of the clays and the efficiency of electric field when applying different direct current. Ultimately, the ability of cutoff was examined through measuring the permeability of the clay cakes derived from the one-dimensional electrophoresis tests.

• Environmental Engineering Research
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• v.25 no.2
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• pp.186-196
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• 2020

Pillared clays with Zr and Fe/Cu/Zr polycations have been prepared from natural clays found in large deposits of Kazakhstan and assessed as catalysts for the catalytic wet peroxide oxidation (CWPO), using 4-nitrophenol (4-NP) as model compound. The performance of the catalysts was followed by measuring the concentration of 4-NP, H₂O₂ and the total organic carbon (TOC), considering C_4-NP = 5 g L^-1, $C_{H_2O_2}$ = 17.8 g L^-1, C_cat = 2.5 g L^-1, initial pH = 3.0 and T = 50℃. At those selected conditions, the pillared clays showed higher activity than natural clays in the CWPO of 4-NP. The conversion of the model pollutant was complete when Fe/Cu/Zr-PILCs were used, with the TOC removal reaching 78.4% after 24 h with the best Fe/Cu/Zr-PILC. The H₂O₂, 4-NP and TOC time-evolution was well described by a kinetic model based on TOC lumps in three blocks, considering the initial TOC (corresponding to 4-NP), the production of oxidizable intermediates and the formation of refractory products.

• Elastomers and Composites
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• v.58 no.1
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• pp.11-16
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• 2023

Electronic skin (e-skin), devices that are mounted on or attached to human skin, have advanced in recent times. Yet, the development of a power supply for e-skin remains a challenge. A stretchable thermoelectric generator is a promising power supply for the e-skin patches. It is a safe and semi-permanent energy harvesting device that uses body heat for generating power. Carbon nanotube (CNT) clays are used in energy-harvesting e-skin patches. In this study, we report improved thermoelectric performance of CNT clays by using chemical doping and physical blending of thermoelectric enhancers. The n-type and p-type thermoelectric enhancers increase electrical conductivity, leading to increased power factors of the thermoelectric CNT clays. The blend of CNT clays and enhancers is intrinsically stretchable up to 50% while maintaining its thermoelectric property.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.171-174
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• 2003

The relationships between compression index, $C_c$, which is the slope of the e-log p curve from consolidation test, and other physical properties of remolded and undisturbed clays were examined. After examined, it is clarified that the $C_c$-initial porosity, $n_0$, relationship is better correlation than the $C_c$-other factors relationship, and a new $C_c$ equations using $n_0$ for remolded and undisturbed clays were suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.161-166
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• 2001

Overconsolidated clays have a different stress history according to the deposit environment. The stress history is classified into (i) rotation angle of stress path, (ii) overconsolidation ratio, and (iii) magnitude of length of recent stress path. Stress-strain behaviour of overconsolidated clays strongly depends on these stress history. In this study a series of drained stress path tests were carried out. Test results indicated that stress-strain behaviour of overconsolidated clay(focused on strain rate) depends on OCR and length of recent stress path, especially rotation angle.