• Journal of Korea Soil Environment Society
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• v.4 no.1
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• pp.57-68
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• 1999

Adsorption behavior of metal elements onto soil minerals such as illite, halloysite. zeolite(clinoptilolite). and goethite was comparatively investigated at $25^{\circ}C$ using pollutant water collected from a gold-bearing metal mine. Speciation of solutions reacted was determined by WATEQ4F program, indicating that most of metal ions exist as free ions and that there is little difference in chemical species and their relative abundances between initial soultion and reacted solutions. The experimental data exhibit that the adsorption extent of elements varies depending on mineral types and reaction time. The adsorption process practically took place within one hour, with Fe and As significantly removed from solutions. On the whole, halloysite is regarded as the most effective adsorbent among minerals used in the experiment. Adsorption properties of alkali elements do not consistent with a manner predicted from hydrated ionic radii.

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.167-171
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• 2016

PURPOSE. This study inspects the effect of incorporating halloysite nanotubes (HNTs) into polymethyl methacrylate (PMMA) resin on its flexural strength, hardness, and Young's modulus. MATERIALS AND METHODS. Four groups of acrylic resin powder were prepared. One group without HNTs was used as a control group and the other three groups contained 0.3, 0.6 and 0.9 wt% HNTs. For each one, flexural strength, Young's modulus and hardness values were measured. One-way ANOVA and Tukey's test were used for comparison (P<.05). RESULTS. At lower concentration (0.3 wt%) of HNT, there was a significant increase of hardness values but no significant increase in both flexural strength and Young's modulus values of PMMA resin. In contrast, at higher concentration (0.6 and 0.9 wt%), there was a significant decrease in hardness values but no significant decrease in flexural strength and Young's modulus values compared to those of the control group. CONCLUSION. Addition of lower concentration of halloysite nanotubes to denture base materials could improve some of their mechanical properties. Improving the mechanical properties of acrylic resin base material could increase the patient satisfaction.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.735-747
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• 1995

The synthesis of clay mineral through the hydrothermal reaction of the anorthite, which is distributed in San Chung-District of Korea and called as the ground rock for halloysite-kaolin, has been investigated. It was observed that this anorthite sample was easily converted into clay mineral with 0.5 wt% HCl solution at a temperature below 20$0^{\circ}C$ under a pressure about 15 atm. The conversion reaction was promoted by adding aluminum chloride under the condition concerned. Aluminum chloride was considered to supply the insufficient aluminum ion during the conversion reaction and to reprepare the acid solution-condition by adding the HCl-component as a by-product. According to the electron micrographs, it was confirmed that fine tubular or needle-shaped halloysite-kaolin minerals with the crystal length shorter than about 1.1${\mu}{\textrm}{m}$ could be obtained by the hydrothermal reaction for 5 days under those conditions.

• Journal of the Korean Ceramic Society
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• v.14 no.2
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• pp.82-87
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• 1977

The material used in this experiment is Ha-Dong kaolin whichis composed of almost crystallographically pure meta-halloysite. It was grinded and passed through 250 mesh and 325 mesh. It was treated with oxalic acids and EDTA which are different in concentration. The samples in conical beaker were kept in laboratory incubator at $25^{\circ}C$ for a certain hours. The treated samples were stirred twice a day. The sample in the conditions as A-7 was kept in an autoclave under the pressure of 3 atmospheric. The samples suspended in each solution were kept for 1.5, 3 and 6 months. The transformation of crystals was detected by X-ray spectrometer, electron microscopy, and infrared spectrometer. The sample through 325 mesh compared with one through 250 mesh was transformed much more. It took for 6 months to transfer from halloysite to kaolinite in EDTA, and 3~4 months under 3 atms in autoclave at the same condition. In oxalic acids it took more than 6 months.

• Journal of the Korean Ceramic Society
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• v.30 no.1
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• pp.41-45
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• 1993

synthesis of artificial kaolinite and the transformation of domestic halloysite have been attempted by means of the hydrothermal treatment. The hydrothermal reaction of the mixtures of gibbsite and amorphous silica was conducted for the synthesis of kaolinite under the pressure of 125MPa at 30$0^{\circ}C$ and especially the seed of kaolinite was added so as to facilitate the synthesis reaction. Domestic pink kaolin of B-grade was hydrothermally treated, in a similar way, for the transformation of crystalline form of it. Boehmite and the artificial kaolinite less than 0.4${\mu}{\textrm}{m}$ could be obtained through the hydrothermal reaction. It could also be found that the majority of hyalloysite was transformed into the plate-type kaolinite through the recrystallization by treating hydrothermally for a long time.

• Journal of the Korean Ceramic Society
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• v.17 no.1
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• pp.13-19
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• 1980

Mineral identifications on halloysite in Hadong-Sancheong area and the halloysite bearing clay ii Yeoju, Yesan and Hampyeong-Muan area are carried out by the method of X-ray diffraction, electron microscopy and DTA. Chemical composition of the above minerals are analyzed by means of X-ray-fluorescence. Refractoriness are also measured by refractoriness tester. A standard diagram for quantitative analysis of halloysite is given.

• Journal of the Mineralogical Society of Korea
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• v.13 no.3
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• pp.121-137
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• 2000

Weathering profiles which were developed under a temperate, humid environment and relatively steep geography, show a thick saprolite and soil horiaon in the Precambrian granitic gneiss of the Yoogoo area. In the weathering profiles, secondary minerals such as interstratified biotite/vermiculite, tri- or di-octahedral vermiculite, halloysite, kaolinite, illite, smectite, gibsite and geothite were observed. Kaolinization of biotite is the most prevalent mechanism but vermiculitization is a minor from all ofweathering profiles. Biotite altered to B/V mixed layer-vermiculite, to illite and to halloysite, kaolinite and gibbsite. Halloysite is the most frequently observed weathering product of biotite in these profiles. Goethite is observed at the around or opened fissures of altered biotite. Tubular halloysite aggregates was fDrmed from dissolution-precipitation of plagioclase. The occurrence of halloysite aggregates is divided into a preferentially oriented type and a wrinkled one which were resulted from the dissolved type of plagioclase. Fe-bearing minerals have also been subjected to dissolution leaving the precipitation of geothite along dissolution voids. The profile of granitic gneiss is a typical weathering pattern showing a clay minerals increase toward the surface. Weathering of minerals were controlled by locally acidic and good-drainage environment, and formed a various and complicated secondary minerals in this study area.

• 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 Industrial Technology
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• v.6
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• pp.49-55
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• 1986

A rapid and simple test to distinguish halloysite from kaolinite in mineral mixtures has been developed based on differences in the rate and extent of formamide intercalation. The results of quantitative analysis by formamide intercalation reaction GEC contained 90% of kaolin minerals, GEC contained of 86% of halloysite and GYK contained of 59% kaolinite. The extent of formamide intercalation by kaolinite was likely influenced by sample crystallinity.

• Journal of the Korean Ceramic Society
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• v.15 no.1
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• pp.21-27
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• 1978

Hadong Kaolin (Halloysite) was granulated cylindrically and treated with 1N aqueous sodium hydroxide solution for 6-48 hrs at 60-10$0^{\circ}C$. The crystalling structure of surface of the products was studied by X-ray powder diffraction method. The reaction rate of halloysite to sodium A zeolite showed a gradual decrease from surface to inner layer. At the surface layer, the reaction mechanism was observed as first order consecutive reaction as follows: halloysitelongrightarrowamorphous aluminosilicatelongrightarrowsodium A zeolitelongrightarrowhydroxysodalite By applying the above reaction mechanism, the rate constants and activation energies was measured.