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류경원,최상훈,Ryu, Kyoung-Won,Choi, Sang-Hoon 대한자원환경지질학회 2017 자원환경지질 Vol.50 No.1
Mineral carbonation for the storage of carbon dioxide is a CCS option that provides an alternative for the more widely advocated method of geological storage in underground formation. Carbonation of magnesium- or calcium-based minerals, especially the carbonation of waste materials and industrial by-products is expanding, even though total amounts of the industrial waste are too small to substantially reduce the $CO_2$ emissions. The mineral carbonation was performed with steelmaking reduction slag as starting material. The steelmaking reduction slag dissolution experiments were conducted in the $H_2SO_4$ and $NH_4NO_3$ solution with concentration range of 0.3 to 1 M at $100^{\circ}C$ and $150^{\circ}C$. The hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at the same leaching temperature. The initial pH of the solution was adjusted to 12 and $CO_2$ partial pressure was 1MPa for the carbonation. The carbonation rate after extracting $Ca^^{2+}$ under $NH_4NO_3$ was higher than that under $H_2SO_4$ and the carbonation rates in 1M $NH_4NO_3$ solution at $150^{\circ}C$ was dramatically enhanced about 93%. In this condition well-faceted rhombohedral calcite, and rod or flower-shaped aragonite were appeared together in products. As the concentration of $H_2SO_4$ increased, the formation of gypsum was predominant and the carbonation rate decreased sharply. Therefore it is considered that the selection of the leaching solution which does not affect the starting material is important in the carbonation reaction. 제강 환원슬래그(steelmaking reduction slag)를 출발물질로 사용하여 다양한 농도의 $H_2SO_4$, $NH_4NO_3$(0.3, 0.5, 0.7, 1 M) 용액, 반응온도 $100^{\circ}C$와 $150^{\circ}C$의 조건에서 Ca 용출 및 탄산화 실험을 실시하였다. 양이온 용출과 탄산화 반응시간은 각각 2시간 및 1시간이었으며 탄산화 효율 증대를 위해 pH는 약 12로 조절하였고 $CO_2$의 부분압은 10 bar이었다. TG 분석결과로부터 탄산화율을 계산한 결과, $H_2SO_4$ 0.5 M과 반응온도 $150^{\circ}C$의 실험 조건에서 약 86%의 고정화율이 관찰되었으나 이 이상의 농도에서는 탄산화율은 급격히 감소하였다. 그러나 $NH_4NO_3$용액을 사용한 결과, 산의 농도가 증가함에 따라 탄산화율도 비례적으로 증가하여 1 M 농도에서 약 93%의 탄산화율이 관찰되었다. 따라서 제강 환원슬래그를 사용한 탄산화반응은 $H_2SO_4$보다는 $NH_4NO_3$용액을 사용할 경우 유리한 것으로 분석되었다. SEM 분석결과, 합성된 아라고나이트는 나무토막 형태(wood piece shape), 둥근형태(round shape), 꽃모양(flower shape)으로 관찰되었으며, 방해석은 결정면이 잘 발달된 능면체형(rhombohedral shape)의 전형적인 형태로 확인되었다.
Effect of Carbon Dioxide Pressure on Mineral Carbonation in Acidic Solutions
류경원,홍석진,최상훈 대한자원환경지질학회 2020 자원환경지질 Vol.53 No.1
Magnesium silicate minerals such as serpentine [Mg3Si2O5(OH)4] have a high potential for the sequestration of CO2; thus, their reactivity toward dissolution under CO2-free and CO2-containing conditions in acidic solvents is a critical process with respect to their carbonation reactions. To examine the carbonation efficiency and dissolution mechanism of serpentine, hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at 100 and 150 oC. The serpentine dissolution experiments were conducted in H2SO4 solution with concentration range of 0.3–1 M and at a CO2 partial pressure of 3 MPa. The initial pH of the solution was adjusted to 13 for the carbonation process. Under CO2-free and CO2-containing conditions, the carbonation efficiency increased in proportion to the concentration of H2SO4 and the reaction temperature. The leaching rate under CO2-containing conditions was higher than that under CO2-free conditions. This suggests that shows the presence of CO2 affects the carbonation reaction. The leaching and carbonation efficiencies at 150 oC in 1 M H2SO4 solution under CO2-containing conditions were 85 and 84%, respectively. The dissolution rate of Mg was higher than that of Si, such that the Mg : Si ratio of the reacted serpentine decreased from the inner part (approximately 1.5) to the outer part (less than 0.1). The resultant silica-rich layer of the reaction product ultimately changed through the Mg-depleted skeletal phase and the pseudo-serpentine phase to the amorphous silica phase. A passivating silica layer was not observed on the outer surface of the reacted serpentine.
류경원,장영남,배인국,서용재,Ryu, Gyoung-Won,Jang, Young-Nam,Bae, In-Kook,Suh, Yong-Jae 대한자원환경지질학회 2008 자원환경지질 Vol.41 No.2
비정질 $SiO_2$와 $Al(OH)_3$를 출발물질로 이용하여 250$^{\circ}C$, $30kg/cm^2$의 조건에서 pH를 2${\sim}$9까지 변화시키면서 캐올리나이트를 수열합성하였다. 합성 캐올리나이트는 XRD, FT-IR, TG, DTA, 및 FE-SEM을 사용하여 광물학적 특성 분석을 실시하였으며, 이로부터 캐올리나이트 합성시 pH의 변화에 따른 영향력을 관찰하였다. 실험결과, 산성조건에서 중-저 결함도와 높은 열적 안정성을 갖는 양호한 캐올리나이트가 합성되었으며, 알카리성 조건에서는 결함이 많은 캐올리나이트가 합성되었다. 이러한 현상은 합성 캐올리나이트의 표면특성이 pH에 의존하기 때문인 것으로 보인다. FT-IR 분석결과, 반응용액의 알칼리도가 증가함에 따라 합성 캐올리나이트의 피크 강도와 분해도가 감소되었으며, TG-DTA 분석결과, 60-70$^{\circ}C$의 저온영역에서의 탈수현상에 의한 피크 강도 증가가 관찰되었다. 이러한 결과는 pH의 증가에 따라 반응에 참여하지 못한 비정질 물질의 양이 증가하기 때문이며 FE-SEM 분석에 의해 확인되었다. Kaolinite [$Al_2Si_2O_5(OH)_4$] used in these experiments was synthesized at 250$^{\circ}C$ for 36 hrs by a hydrothermal process from amorphous $Al(OH)_3$ and $SiO_2$. The change of the mineralogical properties of the phase synthesized were observed in the pH range 2 to 9. The synthetic kaolinite were characterized by the analytical methods of XRD, IR, DIA, and FE-SEM. Kaolinite was obtained in a wide range of pH. The phases with high- to midium- defect kaolinite with high thermal stability were obtained from the acidic conditions and high-defect kaolinite with low thermal stability from the basic conditions. These variations of kaolinite properties appears to be related to the pH dependence of kaolinite surface speciation. The peaks intensity and resolution of the kaolinite decrease according to the alkalinity of the solution by the results of the IR testing. And the peak intensity increases in the 60 to 70$^{\circ}C$ range due to dehydration reaction observed by TG-DTA. Such phenomena was the result of increase of unreacted amorphous materials in the high pH condition, which could be identified by FE-SEM.