Study on the Relationship between Hydration Activity of Calcium Oxide and Characteristics of Precipitated Calcium Carbonate

김정아,Kwang-Suk You,안지환 한국자원공학회 2007 Geosystem engineering Vol.10 No.4

The manufacturing process of precipitated calcium carbonate (PCC) is comprised of three steps. First, calcium oxide is obtained by calcination of limestone. The calcium oxide then turns into calcium hydroxide through a reaction with water (hydration process). Finally, PCC is manufactured by a reaction between the calcium hydroxide and carbonate ions. The hydration process is an exothermic reaction and the hydration activity of calcium oxide is expressed as the heat generated during the hydration process. However, at present there is no standard for the measurement method of the hydration activity of calcium oxide. Therefore, in the present study, we investigated the effect of hydration activity of calcium oxide on the manufacturing process of PCC in order to propose a Korean standard for the measurement of hydration activity of calcium oxide. Based on a comparison of the formation yield of PCC with the hydration activity of calcium oxide measured by various methods, it was verified that the characteristics of PCC are strongly affected by the amount of heat generated for a period of 30 seconds after hydration commences. Therefore, the measurement of hydration activity of calcium oxide for manufacturing PCC should be performed during the initial 30 seconds of hydration. We also confirmed that the formation yield of aragonite PCC increases with increasing hydration activity of calcium oxide. In contrast, calcite PCC decreases.

Study on the Relationship between Hydration Activity of Calcium Oxide and Characteristics of Precipitated Calcium Carbonate

Kim, Jung-Ah,You, Kwang-Suk,Ahn, Ji-Whan 한국암반공학회 2007 Geosystem engineering Vol.10 No.4

The manufacturing process of precipitated calcium carbonate (PCC) is comprised of three steps. First, calcium oxide is obtained by calcination of limestone. The calcium oxide then turns into calcium hydroxide through a reaction with water (hydration process). Finally, PCC is manufactured by a reaction between the calcium hydroxide and carbonate ions. The hydration process is an exothermic reaction and the hydration activity of calcium oxide is expressed as the heat generated during the hydration process. However, at present there is no standard for the measurement method of the hydration activity of calcium oxide. Therefore, in the present study, we investigated the effect of hydration activity of calcium oxide on the manufacturing process of PCC in order to propose a Korean standard for the measurement of hydration activity of calcium oxide. Based on a comparison of the formation yield of PCC with the hydration activity of calcium oxide measured by various methods, it was verified that the characteristics of PCC are strongly affected by the amount of heat generated for a period of 30 seconds after hydration commences. Therefore, the measurement of hydration activity of calcium oxide for manufacturing PCC should be performed during the initial 30 seconds of hydration. We also confirmed that the formation yield of aragonite PCC increases with increasing hydration activity of calcium oxide. In contrast, calcite PCC decreases.

폐기물소각로와 배연탈황공정에 이용하기 위한 흡수제 수화반응 측정 I

정종현(Jong Hyeon Jung),조상원(Sang Won Cho),김영식(Young Sik Kim),이형근(Hyung Keun Lee),오광중(Kwang Joong Oh) 한국환경보건학회 1999 한국환경보건학회지 Vol.25 No.1

The objective of this study is to investigate the hydration reaction and characteristics of Danyang · Backwang limestone/waste shell/shinyo lime. The properties of the waste shell which cause pollution problems were investigated in Southern beach. A limestone/waste shell is selected as an alkali reagent in waste incinerator/flue gas desurfurization processes. The results from above study are as follows. 1. To understand the properties of absorbents, ICP, XRD, EDAX analyses are performed. It is found limestone and waste shell are composed of calcium mostly and some of Na, Mg, Fe, Mn, Si and a few of Cu, Ni and Cd. The main component of waste shell, is calcium of about 38∼39% and lime is about 53∼54% and it becomes 96∼97% in CaCO_3 basis. The limestones from Danyang, Backwang have 53∼55% lime, respectively. 2. During the hydration, the pore structures and surface areas of particles are changed, considerous the expeimental results obtained from the absorbent particles before and after hydration. In the hydration experimental results of lime, 90℃(24 hr) of hydration temperature showed a specific suface area of 11.979㎥/g. The surface areas of limestone sample hydrated with different water temperature as a hydration were 2.3135 ㎥/g, 7.51 ㎥/g, 7.63 ㎥/g, 7.55 ㎥/g, 7.25 ㎥/g, 7.41 ㎥/g, 11.9 ㎥/g, 11.979 ㎥/g. Thus the value at 80∼90℃ hydrated sample is found to be the highest. After hydration, the specific surface area of limestone sample increase but actually does not increase with temperature. This suggest that slurring rate and time might affect hydration condition and the optimum hydration temperature is 80∼90℃. 3. The BET surface area of waste shell and limestone samples was hydrated in 90℃ isothermal condition. So, this increase of specific surface area through hydration can not be predicted in CaCO_3 state. 4. As the hydration temperature increases, the calcinated limestone/seashell/clam sample shows a higher reactivity, but the reactivity of hard shelled mussel sample is lower than that of limestone.

A genome-wide association study in Koreans identifies susceptibility loci for skin hydration

( Mi Ra Choi ),( Jin Hyup Lee ),( Seul Ki Lim ),( Yun Hee Chang ),( Young Ah Shin ),( Hae Eul Lee ),( Myung Im ),( Chang Deok Kim ),( Young Joon Seo ),( Jeung Hoon Lee ),( Young Lee ) 대한피부과학회 2015 대한피부과학회 학술발표대회집 Vol.67 No.2

Background: Skin phenotypes and textures are determined by wrinkle, pigmentation, and hydration and so on. Among these skin phenotypes, skin hydration is a common problem both in elderly and young people. While the genetic factor for skin hydration seems important, the genetic study on skin hydration has not yet been studied. Objectives: We investigated the use of genome-wide association (GWA) analysis to explore molecular basis of skin phenotype of hydration. Methods: A GWAS analysis was conducted to investigate the genetic factors influencing skin hydration in Korean females along with molecular studies of genes in human epidermal keratinocytes for functional study in vitro. Results: GWA study evaluating ~500,000 single nucleotide polymorphisms (SNPs) in 99 Korean females identified five SNPs that were highly associated with skin hydration. We found that a novel SNP in the intron of the single strand binding protein 3 (SSBP3) gene yielded significant replicated associations with skin hydration ability. To confirm these associations, we introduced postconfluent-induced differentiation and high calcium in a keratinocyte culture system model and SSBP3 was upregulated in SVKC in a differentiation dependent manner. Conclusion: Taken together, our results suggest that genetic variants in the intronic region of SSBP3 could be determinants in facial hydration ability of Korean females. SSBP3 represents a new candidate gene to evaluate the molecular basis of the hydration ability in individuals.

Preparation and characterization of high surface area calcium hydroxide sorbent for SO₂ removal

Shin, H.G.,Kim, H.,Kim, Y.N.,Lee, H.S. Elsevier 2009 CURRENT APPLIED PHYSICS Vol.9 No.3

Calcium hydroxides were prepared using novel hydration method and were compared with those obtained by conventional water assisted hydration method and alcohol-water assisted hydration method. In conventional water assisted hydration method and alcohol-water assisted hydration method, raw calcium oxides were hydrated with pure water and alcohol-water solution, respectively, whereas DEG-coated calcium oxides were hydrated with pure water in novel hydration method. Organic coating at the surface of calcium oxide retarded slaking rate and prevented agglomeration during hydration. Calcium hydroxides hydrated with alcohol-water solution and using novel hydration method showed far smaller particle size and less agglomeration than those hydrated with pure water. The specific surface areas of calcium hydroxides hydrated with pure water and alcohol-water solution were 20.13 and 41.23m<SUP>2</SUP>/g, respectively. The specific surface area of calcium hydroxides prepared by novel hydration method was dependent on the contents of water and DEG and ranged from 24.67 to 47.65m<SUP>2</SUP>/g. Through specific surface area and thermo-gravimetric analysis, it was confirmed that the higher the specific surface area of calcium hydroxides, the higher their SO<SUB>2</SUB> reactivity became.

Analysis of the compressive strength development of concrete considering the interactions between hydration and drying

Wang, Xiao-Yong,Park, Ki-Bong Elsevier 2017 Cement and concrete research Vol.102 No.-

<P><B>Abstract</B></P> <P>After removing the formwork, concrete is exposed to environmental air and dries. Due to the interactions between hydration and drying, the strength development of outdoor air-cured concrete is different from that of water-cured concrete or seal-cured concrete. This paper proposes a numerical procedure to evaluate the interactions among cement hydration, moisture diffusion, and compressive strength development. First, by using a desorption isotherm considering the degree of hydration of cement, the relative humidity reduction due to self-desiccation is calculated. Second, a moisture diffusion equation considering the microstructure evolution of concrete is proposed. A hydration model considering the local relative humidity is also put forward. Third, by combining the hydration model with the moisture diffusion model, the individual degree of hydration with varying concrete depths is calculated. Using the individual degree of hydration at different depths, the average degree of hydration is calculated. The compressive strength is evaluated using the average degree of hydration.</P>

Skin electrical property and hydration

( Young Hwan Choi ),( Hyungrye Noh ),( Jong Hee Lee ) 한국피부장벽학회 2022 한국피부장벽학회지 Vol.24 No.2

Skin hydration is one of the most important factors in dermatologic and cosmetic fields. While many factors affect skin hydration, stratum corneum is a key factor determining skin hydration. Electrical properties of the skin including capacitance and conductance are major principles of measuring skin hydration. Devices measuring these electrical properties to evaluate skin hydration have been developed and widely used in research fields and clinical studies. In recent years, a technology using the touch screen panel in the smartphone to measure skin hydration has also been developed. In this review article, we summarize the electrical properties of the skin and studies using different skin hydration measuring devices.

Effect of Fe2O3 additions on the hydration resistance of CaO

Jong-Keun Lee 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.5

Calcium oxide is used as an alkali-resistant material and in the production of refractories despite its low hydration resistance. To increase the hydration resistance, densified structure is required and several studies have been made of the influence on the sintering and increase in the hydration resistance of ceramics based on CaO with various additives. In the present investigation, the effects of an oxide ceramic, Fe2O3, addition on the densification and slaking resistance of CaO were studied based on CaCO3 as a starting material. Iron nitrate was used as the source of Fe2O3 for the control of homogeneous mixing and for less impurities. In addition, the hydration behavior of fused CaO including Fe2O3 was also investigated. CaCO3, involving 0.5 wt% Fe2O3, sintered at 1700 ο C for 1 h showed a dense microstructure and a 8% amount of hydration in comparison with a 25% amount of hydration of pure CaO. The fused amorphous CaO showed a weak structure for resistance to hydration. The CaO samples, which have calcium ferrite products (Ca3Fe15O25 or CaFe3O5) through the slaking testing, showed relatively high hydration resistance. In this study, the hydration behavior of densified CaO with Fe2O3 additive was examined on the basis of the phase and microstructural changes before and after slaking tests.

Validation of biodisplay for measuring skin hydration

( Young Hwan Choi ),( Jong Hee Lee ) 대한피부과학회 2020 대한피부과학회 학술발표대회집 Vol.72 No.1

Background: Skin hydration is one of primary interests in the fields of cosmetics and dermatology. Biodisplay, a novel device to measure skin hydration level, uses a new approach that would provide users skin moisture level by using touch screen panel. Objectives: This study aimed to test the reliability of biodisplay and compared the results with current used device for measuring skin hydration. Methods: We measured skin hydration level at defined points on the face and the arm by Biodisplay and hydration probe of DermaLab Combo. We also measured skin hydration level of the arm after applying moisturizer and after removing moisturizer. After the measurements, we analyzed the reliability of each devices and assessed the correlation of both devices. Results: Total thirty participants were included. Thirteen were males and seventeen were females. The mean age was 38.2. It is shown that biodisplay is reproducible. Skin hydration level measured by the two devices was shown to be correlated. Conclusion: Biodisplay showed reproducibility and correlation with widely used device for measuring skin hydration level. We hope that this study will expand the usage of smartphone-based device in the dermatologic fields.

Preparation and characterization of high surface area calcium hydroxide sorbent for SO2 removal

Hyun-Gyoo Shin,Hwan Kim,Yong-Nam Kim,이희수 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Calcium hydroxides were prepared using novel hydration method and were compared with those obtained by conventional water assisted hydration method and alcohol–water assisted hydration method. In conventional water assisted hydration method and alcohol–water assisted hydration method, raw calcium oxides were hydrated with pure water and alcohol–water solution, respectively, whereas DEG-coated calcium oxides were hydrated with pure water in novel hydration method. Organic coating at the surface of calcium oxide retarded slaking rate and prevented agglomeration during hydration. Calcium hydroxides hydrated with alcohol–water solution and using novel hydration method showed far smaller particle size and less agglomeration than those hydrated with pure water. The specific surface areas of calcium hydroxides hydrated with pure water and alcohol–water solution were 20.13 and 41.23 ㎡/g, respectively. The specific surface area of calcium hydroxides prepared by novel hydration method was dependent on the contents of water and DEG and ranged from 24.67 to 47.65 ㎡/g. Through specific surface area and thermo-gravimetric analysis, it was confirmed that the higher the specific surface area of calcium hydroxides, the higher their SO2 reactivity became.