• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.685-693
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• 1988

From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.180-185
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• 2015

Low-cost ceramic membrane supports with pore sizes in the range of $0.52-0.62{\mu}m$ were successfully prepared by uniaxial dry compaction method using inexpensive raw materials including kaolin, bentonite, talc, sodium borate, and alkaline-earth oxides in carbonate forms (e.g., $MgCO_3$, $CaCO_3$, and $SrCO_3$). The prepared green supports were sintered at $1000^{\circ}C$ for 8 hr in air. The effect of alkaline-earth oxide additives on the flexural strength of clay-based membrane supports was investigated. The porosity of the clay-based membrane supports was found to be in the range of 33-34%. The flexural strength of the clay-based membrane supports with 1% alkaline-earth carbonates was found to be in the range of 42.8-52.7 MPa. The addition of alkaline-earth carbonates to clay-based membrane supports resulted in large increases (47-80%) in the flexural strength of the membrane supports, compared to that of membrane supports without alkaline-earth carbonates. The typical flexural strength of the clay-based membrane support with 1% $SrCO_3$ was 52.7 MPa at 33.8% porosity.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.72-75
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• 2004

The potential of electrokinetic (EK) technology has been successfully demonstrated for the remediation of heavy metal contaminated fine-grained soils through laboratory scale and field application studies. Arsenic contamination in soil is a serious problem affecting both site use and groundwater quality. The EK technology was evaluated for the removal of arsenic from two soil samples: kaolinite clay artificially contaminated with arsenic and arsenic-bearing tailing soil taken from the Myungbong (MB) mining area. The effect of cathodic electrolyte on the process was investigated using three different types of electrolyte: deionized water (DIW), potassium phosphate (KH$_2$PO$_4$) and sodium hydroxide (NaOH). The result of experiments on the kaolinite clay shows that the potassium phosphate was most effective in extracting arsenic, probably resulting from anion exchange of arsenic species by phosphate. On the contrary, the sodium hydroxide seemed to be most efficient in removing arsenic from the tailing soil, and it is explained by the fact that sodium hydroxide increased the soil pH and accelerated ionic migration of arsenic species through increase in desorption and dissolution of arsenic species into pore water.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1049-1051
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• 2000

A chromia-pillared clay has been prepared by ion exchange type intercalation reaction between the sodium ion in montmorillonite and the trimeric chromium oxyformate (TCF) ion, and by subsequent heat-treatment. The structural and thermal properties have been systematically studied by thermal analysis, powder XRD, IR spec-troscopy, and XAS. The gallery height of~6.8 $\AA$ upon intercalation of the TCF ion suggests that the $Cr_3O$ plane is parallel to the aluminosilicate layers. Even though the basal spacing of TCF intercalated clay decreases slightly upon heating, the layer structure was retained up to $550^{\circ}C$ as confirmed by XRD and TG/DTA. Ac-cording to the EXAFS spectroscopic analysis, it is identified that the (Cr-Cr) distance of 3.28 $\AA$ between vertex-linked CrO6 octahedra in TCF splits into 2.64 $\AA$, 2.98 $\AA$, and 3.77 $\AA$ due to the face-, edge-, and corner-shared CrO6 octahedra after heating at $400^{\circ}C$, implying that a nano-sized chromium oxide phase was stabilized within the interlayer space of clay.

• Current Research on Agriculture and Life Sciences
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• v.31 no.1
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• pp.18-24
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• 2013

This work attempted to fabricate organic/inorganic nanocomposite by combining organic cellulose nanofibrils (CNFs), isolated by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation of native cellulose with inorganic nanoclay. The morphology and dimension of CNFs, and tensile properties and thermal stability of CNF/clay nanocomposites were characterized by transmission electron microscope (TEM), tensile test, and thermogravimetry (TG), respectively. TEM observation showed that CNFs were fibrillated structure with a diameter of about $4.86{\pm}1.341nm$. Tensile strength and modulus of the hybrid nanocomposite decreased as the clay content of the nanocomposite increased, indicating a poor dispersion of CNFs or inefficient stress transfer between the CNFs and clay. The elongation at break increased at 1% clay level and then continuously decreased as the clay content increased, suggesting increased brittleness. Analysis of TG and derivative thermogravimetry (DTG) curves of the nanocomposites identified two thermal degradation peak temperatures ($T_{p1}$ and $T_{p2}$), which suggested thermal decomposition of the nanocomposites to be a two steps-process. We think that $T_{p1}$ values from $219.6^{\circ}C$ to $235^{\circ}C$ resulted from the sodium carboxylate groups in the CNFs, and that $T_{p2}$ values from $267^{\circ}C$ to $273.5^{\circ}C$ were mainly responsible for the thermal decomposition of crystalline cellulose in the nanocomposite. An increase in the clay level of the CNF/clay nanocomposite predominately affected $T_{p2}$ values, which continuously increased as the clay content increased. These results indicate that the addition of clay improved thermal stability of the CNF/clay nanocomposite but at the expense of nanocomposite's tensile properties.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.85-93
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• 1988

This laboratory study was carried out in order to produce fundamental data for analyzing salt movement and desalinization effects, using samples of silt loam soil collected in Gyehwado and Daeho reclaimed tidelans, and samples of silty clay loam soil collected in Kimie tideland. Desalinization experiments with gypsum treatment were performed to analyze changes of the hydraulicc conductivity with changes of the soil property and the salt concentration during the desalinization of reclaimed tideland soils by leaching through the subsufface drainage, and correlations between factors infl uencing the reclamation of salt affected soils were analyzed by the statistical method. The results were summarized as follows: 1. The reclaimed tideland soils used in this study were saline-sodic soils with the high exchangeable sodium percentage and the high electrical conductivity. 2. Changes of the hydraulic conductivity with the amount of leaching water and the leaching time elapsed were affected by the amount of gypsum except exchangeable sodium and clay contents. The regression equation between the depth of water leached per unit depth of soil (Dw / Ds : X) or the square root of the leaching time elapsed (T $^1$ $^2$ : X) and the relative hydraulic conductivity (HCr:Y) could be expressed in Y=a . bx. 3. The more exchangeable sodium and clay contents regardless of the amount of gypsum, the more the leaching time was required until a given volume of water was leached through the soil profile. The regression analysis showed that the relationship between the depth of water leached per unit depth of soil(Dw /Ds:X) and the square root of the leaching time elapsed(T$^1$$^2$ :Y) could be described by Y=a . Xb. 4. The hydraulic conductivity was influenced to a major degree by the salt concentration provided that the electrical conductivity was below 10 mmhos / cm during the desalinization of reclaimed tideland soils. The regression equation between the relative electrical conductivity ( ECr : X) and the relative hydraulic conductivity (HCr:Y) could be expressed in Y=a + b . X-$^1$. 5. In conclusion, the hydraulic conductivity, leaching requirements and the leaching time elapsed can be estimated when the salt concentration decreases to a certain level during the desalinization of reclaimed tidelands, and the results may be applied to the analysis of salt movement and desalinization effects.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.467-472
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• 2015

The effect of $SrCO_3$ content on the microstructure, porosity, flexural strength, and pore size distribution of clay-based membrane supports was investigated. Green compacts prepared from low cost materials such as kaolin, bentonite, talc, sodium borate, and strontium carbonate were sintered at $1000^{\circ}C$ for 8 h in air. It was possible to control the porosity of the clay-based membrane supports within the range of 33% to 37% by adjusting the $SrCO_3$ content. The flexural strength of the clay-based membrane supports was found to strongly depend on their porosity. In turn, the porosity was affected by the $SrCO_3$ content. The average pore size and flexural strength of the clay-based membrane supports containing 4 wt% $SrCO_3$ were $0.62{\mu}m$ and 33 MPa at 34% porosity.

• Polymer(Korea)
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• v.32 no.4
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• pp.347-352
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• 2008

High impact polystyrene (HIPS) nanocomposites with organically modified montmorillonite (organoclay) via in situ polymerization were synthesized, and the effects of organoclay incorporation on material properties were investigated. Organoclays having a reactive group, vinylbenzyltrimethyl clay (VBC) and octadecylvinylbenzyldimethyl clay (ODVC), were prepared by the ion-exchange reactions of sodium montmorillonite with vinylbenzyltrimethyl ammonium chloride (VBTMAC) and octadecylvinylbenzyldimethyl ammonium bromide (ODVBDAB), respectively, and a commercial organoclay, $Cloisite^{(R)}$ 10A(C10A), was used for comparison. It was confirmed that the X-ray diffraction (XRD) peak of the nanocomposites prepared by ODVC disappeared, which indicates the exfoliation of silicate layers. On the contrary, the XRD peak of the nanocomposites prepared by C10A shifted to lower angle, indicative of the intercalation of polymer chains into silicate layers. Rheological properties such as storage modulus and complex viscosity increased with increasing organoclay.

• Journal of the Korean Applied Science and Technology
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• v.20 no.3
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• pp.243-250
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• 2003

Poly(methyl methacrylate)/clay nanocomposite particles with particle size of 275${\sim}$292 nm range were successfully prepared using emulsion polymerization. The content of montmorillonite based on the methyl methacrylate monomer was chosen as 30 wt.%. 2,2-azobis(isobuthylamidine hydrochloride) and n-dodecyltrimethylammonium chloride were used as an initiator and a surfactant in cationic emulsion system. Potassium persulfate and sodium lauryl sulfate were used as an initiator and a surfactant in anionic emulsion system. The evidence of intercalated /exfoliated structure of montmorillonite in the nanocomposite prepared in our experiment was confirmed by wide angle x-ray diffraction patterns of $d_{001}$ plane. Thermal behavior of nanocomposite was traced using DSC and TGA. It was found that the nanocomposite particle prepared by cationic emulsion system showed intercalated structured. We also found that the nanocomposite particle obtained from anionic emulsion system resulted in the fully exfoliated structure.

• Polymer(Korea)
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• v.26 no.3
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• pp.375-380
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• 2002

Diamines (p-phenylenediamine , m-phenylenediamine , and n-hexamethylenediamine) were intercalated into sodium montmorillonite for the further reaction with the anhydride end groups of polyamic acid. The anhydride terminated polyamic acid was synthesized using a mole ratio of 4,4'-oxydianilline : 1,2,4,5-benzene tetracarboxylic dianhydride = 1.50 : 1.53. The modified montmorillonite was reacted with polyamic acid terminated with anhydride group in N-methyl-2-pyrrolidone (polyamic acid/clay nanocomposite). After imidization, thin films of the polyimide/clay nanocomposite were prepared. From the results of XRD and TEM, we found that mono layered silicates were dispersed in polyimide matrix and those resultants were exfoliated nanocomposites. Mechanical properties of exfoliated polyimide nanocomposite were better than both those of pure polyimide and those of intercalated polyimide nanocomposite.