• Economic and Environmental Geology
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• v.42 no.5
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• pp.495-500
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• 2009

Actinide sorption to the geological materials can reduce the mobility and bioavailability of radionuclides released to the environment through the development of nuclear weapons and nuclear energy. Under circumneutral pH conditions, actinide sorption can be enhanced by phosphate anions sorbed on oxide mineral surfaces as indicated by the sorption of trivalent lanthanide ions ($Ln^{3+}$), the chemical analog for trivalent actinide ions ($Ac^{3+}$). In this paper, we examined a ternary sorption system of trivalent europium ions ($Eu^{3+}$) sorbed onto boehmite (${\gamma}$-AlOOH) surfaces pre-sorbed with phosphate anions (${PO_4}^{3-}$), using extended X-ray absorption fine structure (EXAFS) spectroscopy. In the Eu-$PO_4$-boehmite ternary sorption system, $EuPO_4$ surface precipitates were formed as implicated by Eu $L_{III}$-edge EXAFS spectroscopy. Phosphorus K-edge EXAFS fingerprinting indicated a bidentate mononuclear surface complex formation of phosphate sorbed on boehmite surfaces as well as $EuPO_4$ surface precipitate formation.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.241-248
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• 2009

Kaolinite was synthesized from amorphous $SiO_2$ and $Al(OH)_3{\cdot}xH_{2}O$ as starting materials by hydrothermal reaction conducted at $250^{\circ}C$ and $30\;kg/cm^2$. The acidity of the solution was adjusted at pH 2. The synthesized kaolinite was characterized by XRD, IR, NMR, FE-SEM, TEM and EDS to clarify the formational process according to the reaction time from 2 to 36 hours. X-ray diffraction patterns showed after 2 h of reaction time, the starting material amorphous $Al(OH)_3{\cdot}xH_{2}O$ transformed to boehmite (AlOOH) and after the reaction time 5 h, the peaks of boehmite were observed to be absent thereby indicating the crystal structure is partially destructed. Kaolinite formation was identified in the product obtained after 10 h of reaction and the peak intensity of kaolinite increased further with reaction time. The results of TGA and DTA revealed that the principal feature of kaolinite trace are well resolved. TGA results showed 13 wt% amount of weight loss and DTA analysis showed that exothermic peak of boehmite observed at $258^{\circ}C$ was decreased gradually and after 10 h of reaction time, it was disappeared. After 5 h of the reaction time, the exothermicpeak of transformation to spinel phase was observed and the peak intensiy increased with reaction time. The results of FT-IR suggested a highly ordered kaolinite was obtained after 36 hours of reaction. It was identified by the characteristic hydroxide group bands positioned at 3,696, 3670, 3653 and $3620\;cm^{-1}$. The development of the hydroxyl stretching between 3696 and $3620\;cm^{-1}$, depends on the degree of order and crystalline perfection. TEM results showed that after 15 h reaction time, curved platy kaolinite was observed as growing of (001) plane and after 36 h, the morphology of synthetic kaolinite exhibited platy crystal with partial polygonal outlines.

• The Journal of the Petrological Society of Korea
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• v.22 no.1
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• pp.1-8
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• 2013

Physical properties, XRF, UV-Vis, FTIR studies were carried out in order to characterize gemological features of ruby from Tajikistan. Fluorescence reaction of the Tajikistan ruby to short wave ultraviolet was moderate to very strong in red and long wave ultraviolet rays was weakly detected. UV-visible analysis strong absorption bands at 468.5, 475, 476.5 nm and broaden bands at 550 nm were observed for ruby due to $Cr^{3+}$. According to FT-IR analysis, all rubies from Tajikistan showed the similar patterns and kaolinite peaks at 3500, 3617, 3630, $3677cm^{-1}$ and boehmite broaden absorption bands at 3085 and $3320cm^{-1}$. Inclusions in Tajikistan ruby are observed solid inclusions, negative crystals, needle and silk inclusions. These distinctive characteristics mentioned above can be used to identify the locality and source of ruby stones from Tajikistan.