• Journal of the Korea Institute of Building Construction
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• v.18 no.5
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• pp.403-412
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• 2018

Recently, needs for utilization of recycled aggregate have been increasing. However, its utilization has been limited due to its high alkalinity, which mostly came from the unremoved cement paste particles that were attached at the surface of recycled aggregate. Various efforts has been made to reduce its alkalinity by using $CO_2$, but currently available methods that uses $CO_2$ generate the problem with pH recovery. Considering the fact that supercritical $CO_2$ ($scCO_2$) can provide more rapid carbonation of cement paste than by normal $CO_2$, $scCO_2$ was utilized in this work. The reaction between $scCO_2$ and hydrated cement paste has been systematically evaluated. According to the results, it was found that powder type showed higher carbonation compared to that of cube specimens. It seems the carbonation by $scCO_2$ has occurred only at the surface of the specimen, and therefore still showed some amount of $Ca(OH)_2$ calcium aluminates after reaction with $scCO_2$. With powder type specimen, all $Ca(OH)_2$ was converted into $CaCO_3$. Moreover, additional calcium that came from both calcium aluminate hydrates and calcium silicate hydrates reacted with $scCO_2$ to form $CaCO_3$. After carbonation with $scCO_2$, the powder type specimen did not show pH recovery, but cube specimens did show due to the presence of portlandite.

• Polymer(Korea)
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• v.31 no.2
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• pp.168-176
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• 2007

The sub-micron particles of poly ($\gamma-glutamic$ acid) (PGA) containing lysozyme have been prepared using supercritical antisolvent (SAS) precipitation process at various experimental conditions such as pressure, temperature, inner diameter of nozzle, and concentration. As overall results of the application of SAS process to this system, the smaller size powder has been produced as (i) increasing pressure, (ii) decreasing temperature, (iii) decreasing the inner diameter of nozzle, and (iv) decreasing the concentration of PGA and lysozyme. It is found by means of FT-IR analysis that during SAS process, the composition has changed from the original composition of PGA : lysozyme=50 : 50 into PGA : lysozyme=33 : 67 at final product powder. It means that PGA has higher solubility for the mixed solvent of carbon dioxide and dimethyl sulfoxide (DMSO). Due to such difference of solubility, this particle forms the core-shell structure of which the core consists mainly of lysozyme. It is also found that the residual DMSO amount of $7.8\times10^{-3}wt%$ exists inside the powder.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.33-40
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• 2021

The objective of this work is to prove a possibility of void f illing through a carbonation f or the purpose of improving the quality of recycled aggregate. Carbonation can permanently immobilize CO2, which is a greenhouse gas, and thus provides additional benefit on environment. In this work, recycled fine aggregate was reacted using gaseous CO2 and supercritical CO2(scCO2) in a closed chamber, and the changes in physical properties of the recycled f ine aggregate bef ore and af ter carbonation were analyzed using the apparent density, skeletal density, pH, and FE-SEM measurements. Thereafter, a mortar specimen was prepared and a compressive strength was measured. According to the experimental results, it was found that the increase in the apparent density and the true density was higher by the reaction with scCO2, which was conducted at high temperature and high pressure compared to the reaction with gaseous CO2. In addition, the pH of the eluted water was found to have a larger initial decrease than that observed with samples from reaction by gaseous CO2. The shape and amount of calcium carbonate crystals were also found to be larger than that from gaseous CO2. The increase in compressive strength was the largest when using recycled fine aggregate reacted with scCO2. It was clear that quality improvement of recycled fine aggregate was higher with scCO2 than with gaseous CO2.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.644-651
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• 2012

We have investigated the effect of lard fraction extracted with supercritical carbon dioxide (SC-$CO_2$) on the flavor enhancement of maillard reaction product (MRP) based meat flavors. MRP based meat flavors were prepared with low glutamic acid (Glu) hydrolyzed wheat gluten (NaCl concentration: 7.61%(w/v)), ribose, cysteine, garlic juice powder, protease-digested Lentinus edodes powder and lard fractions extracted with SC-$CO_2$. Lard was extracted with SC-$CO_2$ at each of three temperatures (40, 60, and $80^{\circ}C$) and at each of four pressures (30, 40, 50, and 60 MPa). Obtained lard SC-$CO_2$ fractions and MRP based meat flavors with those fractions were analyzed for their total yield, aroma pattern by SMart nose system, and sensorial properties. The extraction yield had no difference as temperature increased from $40^{\circ}C$ to $60^{\circ}C$ and even decreased at $80^{\circ}C$. However, increase in pressure level at $40^{\circ}C$ drastically increased the extraction yield. The aroma patterns of raw lard and lard SC-$CO_2$ fractions with 30 MPa were significantly discriminated from those of SC-$CO_2$ lard fractions extracted with higher pressure by SMart nose system. Aroma pattern of MRP based meat flavors with higher pressure extracted lard fractions also showed significant difference through pattern analysis by the SMart nose system. The MRP based meat flavor with lard SC-$CO_2$ fractions at 50 and 60 MPa were described as less sulfuric, less pungent, and more balanced in roasted meat and sweet attributes from sensory evaluation.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.67-75
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• 2012

Carbon-dioxide capture and storage (CCS) process is consisted by capturing carbon-dioxide from large point source such as power plant and steel works, transporting and sequestrating captured $CO_2$ in a stable geological structure. During CCS process, it is inevitable of introducing impurities from combustion, capture and purification process into $CO_2$ stream. Impurities such as $SO_2$, $H_2O$, CO, $N_2$, Ar, $O_2$, $H_2$, can influence on process efficiency, capital expenditure, operation expense of CCS process. In this study, experimental apparatus is built to simulate the behavior of $CO_2$ transport under various impurity composition and process pressure condition. With this apparatus, $N_2$ impurity effect on $CO_2$ mixture transportation was experimentally evaluated. The result showed that as $N_2$ ratio increased pressure drop per mass flow and specific volume of $CO_2-N_2$ mixture also increased. In 120 and 100 bar condition the mixture was in single phase supercritical condition, and as $N_2$ ratio increased gradient of specific volume change and pressure drop per mass flow did not change largely compared to low pressure condition. In 70 bar condition the mixture phase changed from single phase liquid to single phase vapor through liquid-vapor two phase region, and it showed that the gradient of specific volume change and pressure drop per mass flow varied in each phase.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.431-437
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• 2005

Overall experiments were planned by central composite design, and results were analyzed by response surface methodology (RSM) to determine effects of three independent variables, temperature ($X_{1}$), extraction time ($X_{3}$), and pressure ($X_{3}$), on yield of sesame oil extract (Y). Regression equation model optimized by response surface analysis was: Y (sesame oil) = $-3.89+0.07X_{1}+0.03X_{2}+0.0006X_{3}-0.0007X_{1}^{2}-0.0002X_{2}X_{1}-0.00008X_{2}^{2}+0.000004X_{3}X_{1}+0.0000009X_{3}X_{2}-0.00000009X_{3}^{2}$. According to RSM analysis, optimum extracting conditions of temperature, time, and pressure were $45.89^{\circ}C$, 131.89 min, and 34228.41 kPa, respectively, and statistical maximum yield of sesame oil was 96.27%. Fatty acid composition of sesame oil showed sesame oil extracted by Supereritical Fluid $CO_{2}$ contained lower levels of palmitic, stcaric, and oleic acids and higher levels or palmitoleic and linoleic acids than commercial sesame oil. Commercial and extracted sesame oils were analyzed by electronic nose composed of 12 different metal oxide sensors. Obtained data were interpreted by statistical method of MANOVA. Sensitivities of sensors from electronic nose were analysed by principal component analysis. Proportion of first principal component was 99.92%. All sesame oils showed different odors (p < 0.05).

• Korean Journal of Agricultural Science
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• v.43 no.2
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• pp.249-257
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• 2016

In this study, rapeseed extracts were obtained by supercritical carbon dioxide fluid extraction of defatted rapeseed to evaluate the stability and antioxidant activity of an oil-in-water (O/W) emulsion system. The oil-in-water emulsions were prepared from stripped soybean oil with different concentrations (0.3, 0.4, 0.5, and 0.6%) of rapeseed extract as an emulsifier. Their emulsion stability was compared to that of emulsions prepared with the commercial emulsifier, Tween 20 (Polysorbate 20, 0.2%). After stripping the soybean oil, the total tocopherol content was reduced from 51.4 g/100 g to 1.1 g/100 g. Emulsion stability and oxidative stability of emulsions prepared with Tween 20 and rapeseed extract as emulsifiers were evaluated. For 30 days droplet sizes of emulsions containing rapeseed extract (0.4, 0.5, and 0.6%) were not significantly different (p > 0.05). Similar results were obtained for emulsion stability (ES) and Turbiscan analysis, suggesting that the addition of rapeseed extract increased emulsion stability. The addition of rapeseed extract at more than 0.4% resulted in an emulsion stability comparable to the addition of 0.2% Tween 20. The antioxidative ability of rapeseed extract increased with the amount added in the emulsion. Moreover, the addition of 0.6% rapeseed extract resulted in the lowest emulsion peroxide values (10.3 mEq/L) among all treatments. Therefore, according to the stability of its antioxidative and physical stability properties, rapeseed extract from super critical extraction could be successfully applied to the food and cosmetic industries.

• Proceedings of the Korea Society of Poultry Science Conference
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• 2000.04a
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• pp.23-36
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• 2000

Hurdle technique was used to remove cholesterol efficiently from liquid egg yolk. The quality of the low cholesterol egg products from the process were evaluated. From the 75 % cholesterol reduced egg yolk through $\beta$-cyclodextrin treatment. 2 times weight of soy bean oil was added to the egg yolk and homogenized followed by centrifuged to be maximized to remove cholesterol. When the pH of the yolk was adjusted to 9, 92 % of cholesterol was removed while 95.4 % of cholesterol was removed when 3 times weight of soy bean oil was added to the egg yolk. As the results of application of supercritical carbon dioxide extraction to the 75 % cholesterol reduced egg yolk through ${\beta}$-cyclodextrin treatment, 92.5 % of the cholesterol was removed from the egg yolk at $35^{\circ}C$, 4,500 psi, for 4 hours under co-solvent. The quality characteristics of the produced low cholesterol egg products were analysed. The cholesterol reduced egg yolk produced from ${\beta}$-cyclodextrin and soy bean oil treatment showed the lower emulsion capacity compared with control. The fatty acid composition of the cholesterol reduced egg yolk produced from ${\bet}a$-cyclodextrin and soy bean oil treatment showed increased C18:2 and C18:3 compared with control while decreased C16:1 and C18: 1 compared with control. The saponification method with extracting solvent of hexane showed that cholesterol concentration was 28.1 %. The quantity of hydrolysis solution(95 % ethanol : 33 % KOH = 94 : 6) was varied from 40 to 80 times of sample weights and the cholesterol concentration of 35.7 % was the highest result in the 60 times(v/w) hydrolysis solution. Cholesterol concentration of 35.7 % was recovered at the first trial with saponification method. but it could be improved up to 95.7 % after 4 times repetitive purification.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.285-295
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• 2014

Citrus essential oil were extracted from citron peel of cultivated in Gohong (CCP) using environmentally friendly supercritical carbon dioxide method. Antioxidant activity and aroma composition of the essential oils extracted by the SC-$CO_2$ method were evaluated by comparing with those extracted by organic solvent method. Fatty acid composition, DPPH scavenging, and antioxidant activity of the oils obtained by different extraction condition of SC-$CO_2$ method were investigated and their antioxidant activities were compared with commercially available lavender, eucalyptus and tea tree oils. As the results, linoleic acid was most abundantly found from CCP oil extracted by the SC-$CO_2$ method and cis-11,144-eicosadienoic acids was second abundantly found. Radical scavenging ability of DPPH was 98% when the concentration of CCP oil was 50 mg/mL. This scavenging ability increased with the increase of oil concentration. On the other hand, flavonoids content (84 mg/100g) of the CCP oil extracted by the SC-$CO_2$ method was slightly higher than that (75 mg/100g) by hexane extraction. The results, obtained from CCP oil by GC-MS, indicated that, among 66 components, the content of terpenes was 55.8% and limonene was 27.3%.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.763-767
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• 2010

High-pressure phase behavior for the binary mixture of 1-propanol with supercritical $CO_2$ has been measured by means of a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The equilibrium loci of the pressure - composition and pressure - temperature were obtained for the binary mixture of 1-propanol + $CO_2$ system at 305.15 K, 313.15 K, 323.15 K and 333.15 K, and from 2 MPa to 11 MPa. The critical temperature of the mixture increased with the temperature. The pressure-composition line for the binary mixture of $CO_2$-1-propanol system showed a typical type-II phase behavior. The experimental P-x envelopes were correlated by using the Peng-Robinson equation of state in a satisfactory manner to obtain the parameters with $k_{ij}=0.116$ and ${\eta}_{ij}=-0.065$.