• 제목/요약/키워드: dissolution temperature

검색결과 415건 처리시간 0.025초

Dissolution of North Korean Magnesite by using Hydrochloric Acid

  • Baek, Ui-Hyun;Park, Hyungkyu;Lee, Jin-Young;Kang, Jungshin
    • Korean Chemical Engineering Research
    • /
    • 제55권5호
    • /
    • pp.711-717
    • /
    • 2017
  • A fundamental study was conducted on the dissolution of North Korean magnesite using hydrochloric acid to understand the dissolution behavior of the magnesium and impurities. The influence of the acid concentration, particle size of the magnesite, reaction temperature, and pulp density on the dissolution of magnesium, iron, calcium, aluminum, and silicon dioxide was studied. The experimental results showed that 98.5% of magnesium, 86.9% of iron, 87.3% of calcium, 23.6% of aluminum, and 20.4% of silicon dioxide were dissolved when magnesite particle sizes within the range of $75{\sim}105{\mu}m$ were reacted using 3 M HCl solution under 6% pulp density at 363 K for 3 h. The residues that remained after the dissolution were silicon dioxide, talc, and clinochlore.

Glass Dissolution Rates From MCC-1 and Flow-Through Tests

  • Jeong, Seung-Young
    • 한국방사성폐기물학회:학술대회논문집
    • /
    • 한국방사성폐기물학회 2004년도 학술논문집
    • /
    • pp.257-258
    • /
    • 2004
  • The dose from radionuclides released from high-level radioactive waste (HLW) glasses as they corrode must be taken into account when assessing the performance of a disposal system. In the performance assessment (PA) calculations conducted for the proposed Yucca Mountain, Nevada, disposal system, the release of radionuclides is conservatively assumed to occur at the same rate the glass matrix dissolves. A simple model was developed to calculate the glass dissolution rate of HLW glasses in these PA calculations [1]. For the PA calculations that were conducted for Site Recommendation, it was necessary to identify ranges of parameter values that bounded the dissolution rates of the wide range of HLW glass compositions that will be disposed. The values and ranges of the model parameters for the pH and temperature dependencies were extracted from the results of SPFT, static leach tests, and Soxhlet tests available in the literature. Static leach tests were conducted with a range of glass compositions to measure values for the glass composition parameter. The glass dissolution rate depends on temperature, pH, and the compositions of the glass and solution, The dissolution rate is calculated using Eq. 1: $rate{\;}={\;}k_{o}10^{(ph){\eta})}{\cdot}e^{(-Ea/RT)}{\cdot}(1-Q/K){\;}+{\;}k_{long}$ where $k_{0},\;{\eta}$ and Eaare the parameters for glass composition, pH, $\eta$ and temperature dependence, respectively, and R is the gas constant. The term (1-Q/K) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_{0},\;{\eta}\;and\;E_{a}$ are the parameters for glass composition, pH, and temperature dependence, respectively, and R is the gas constant. The term (1-Q/C) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_0$, and Ea are determined under test conditions where the value of Q is maintained near zero, so that the value of the affinity term remains near 1. The dissolution rate under conditions in which the value of the affinity term is near 1 is referred to as the forward rate. This is the highest dissolution rate that can occur at a particular pH and temperature. The value of the parameter K is determined from experiments in which the value of the ion activity product approaches the value of K. This results in a decrease in the value of the affinity term and the dissolution rate. The highly dilute solutions required to measure the forward rate and extract values for $k_0$, $\eta$, and Ea can be maintained by conducting dynamic tests in which the test solution is removed from the reaction cell and replaced with fresh solution. In the single-pass flow-through (PFT) test method, this is done by continuously pumping the test solution through the reaction cell. Alternatively, static tests can be conducted with sufficient solution volume that the solution concentrations of dissolved glass components do not increase significantly during the test. Both the SPFT and static tests can ve conducted for a wide range of pH values and temperatures. Both static and SPFt tests have short-comings. the SPFT test requires analysis of several solutions (typically 6-10) at each of several flow rates to determine the glass dissolution rate at each pH and temperature. As will be shown, the rate measured in an SPFt test depends on the solution flow rate. The solutions in static tests will eventually become concentrated enough to affect the dissolution rate. In both the SPFt and static test methods. a compromise is required between the need to minimize the effects of dissolved components on the dissolution rate and the need to attain solution concentrations that are high enough to analyze. In the paper, we compare the results of static leach tests and SPFT tests conducted with simple 5-component glass to confirm the equivalence of SPFT tests and static tests conducted with pH buffer solutions. Tests were conducted over the range pH values that are most relevant for waste glass disssolution in a disposal system. The glass and temperature used in the tests were selected to allow direct comparison with SPFT tests conducted previously. The ability to measure parameter values with more than one test method and an understanding of how the rate measured in each test is affected by various test parameters provides added confidence to the measured values. The dissolution rate of a simple 5-component glass was measured at pH values of 6.2, 8.3, and 9.6 and $70^{\circ}C$ using static tests and single-pass flow-through (SPFT) tests. Similar rates were measured with the two methods. However, the measured rates are about 10X higher than the rates measured previously for a glass having the same composition using an SPFT test method. Differences are attributed to effects of the solution flow rate on the glass dissolution reate and how the specific surface area of crushed glass is estimated. This comparison indicates the need to standardize the SPFT test procedure.

  • PDF

시차주사열량측정법에 의한 니켈기 초내열 합금의 열분석 (Thermal Analysis of Nickel-Base Superalloys by Differential Scanning Calorimetry)

  • 윤지현;오준협;김홍규;윤존도
    • 한국재료학회지
    • /
    • 제26권5호
    • /
    • pp.235-240
    • /
    • 2016
  • Appropriate thermo-mechanical properties of nickel-based superalloys are achieved by heat treatment, which induces precipitation and solid solution hardening; thus, information on the temperature ranges of precipitation and dissolution of the precipitates is essential for the determination of the heat treatment condition. In this study, thermal analyses of nickel-based superalloys were performed by differential scanning calorimetry method under conditions of various heating rates of 5, 10, 20, or 40K/min in a temperature range of 298~1573K. Precipitation and dissolution temperatures were determined by measuring peak temperatures, constructing trend lines, and extrapolating those lines to the zero heating rate to find the exact temperature under isothermal condition. Determined temperatures for the precipitation reactions were 813, 952, and 1062K. Determined onset, peak, and offset temperatures of the first dissolution reaction were 1302, 1388, and 1406K, respectively, and those values of the second dissolution reaction were 1405, 1414, and 1462K. Determined solvus temperature was 1462K. The study showed that it was possible to use a simple method to obtain accurate phase transition temperatures under isothermal condition.

고체철-용융아연의 용해반응 (The Dissolving Reaction of Solid Iron with Molten Zinc)

  • 윤병하;정인상;박경채
    • 한국표면공학회지
    • /
    • 제9권2호
    • /
    • pp.1-7
    • /
    • 1976
  • The dissolving and growth kinetics of intermetallic compounds for the reaction between solid iron and molten zinc were studied under nitorgen atmosphere over the temperature range between470$^{\circ}C$ and 680$^{\circ}C$. The rates of dissolution of solid iron into molten zinc were obtained under a static conditon, The amount of dissolution of sold iron and the growth of intermetalic compounds could be determined by means of microscopy. The thickness of intermetallic compound at a given temperature increases with increasing time, whereas for a given time decreases with increasing temperature . The rate of dissolution is controlled by the diffusion process of iron in the effective boundary layer of molten zinc over the temperature range 470$^{\circ}$-530$^{\circ}C$, 570$^{\circ}$-620$^{\circ}C$, and 650$^{\circ}$-665$^{\circ}C$, while by the surface reaction over the range 530$^{\circ}$-570$^{\circ}C$ and 620$^{\circ}$-650$^{\circ}C$.

  • PDF

용융법에 의한 수용성 유리의 제조 및 특성 (I) : 용해 특성, 살균 효과 및 세포 독성 (Preparation and Characterization of Water-Soluble Glass through Melting Process (I) : Dissolution Characteristics, Bactericidal Effects and Cytotoxicity)

  • 조종호;이용근;최세영;신철수;김경남
    • 한국세라믹학회지
    • /
    • 제32권10호
    • /
    • pp.1093-1102
    • /
    • 1995
  • Water-soluble phosphate glasses containing Ag or Cu ion were prepared through melting process. Then the powdered glass samples were dissolved in D.I. water at room temperature with changing the dissolution time. In terms with the glass composition, dissolution characteristics, bactericidal effects and cytotoxicities were investigated. Dissolved amounts increased uniformly with dissolution time, and the dissolution rate was higher for ternary glass than for binary glass and with less metal oxide amount. And the dissolution rate of the glass with Ag ion was higher than that with Cu ion, and the bactericidal effect of the glass with Ag ion was also greater. Solution with more than 25 ppm of Ag was observed to have strong cytotoxicity to L929, and solutions of lower Ag concentration or with Cu seemed to have little cytotoxicity.

  • PDF

Sulpiride의 Polymorphism 및 그 약제학적(藥劑學的) 연구(硏究) (제3보)(第三報) -Polymorph에 따른 용출속도(溶出速度)- (Polymorphism of Sulpiride and Its Pharmaceutical Applications ( III ) -Dissolution Kinetics of Sulpiride Polymorphs-)

  • 이민화;김길수
    • Journal of Pharmaceutical Investigation
    • /
    • 제12권3호
    • /
    • pp.55-63
    • /
    • 1982
  • The dissolution kinetics for polymorphs of sulpiride, the effect of polyethylene glycol 4000 on the dissolution kinetics of sulpiride polymorphs and the dissolution rate difference between the tablets of polymorph form I and form II were investigated. The results could be summerized as followings: 1. The dissolution rates of two polymorphs of sulpiride were significantly different and the thermodynamic parameters calculated from dissolution kinetics were as follows; transition temperature $98^{\circ}C$, enthalpy change, -2.108 kcal/mole, free energy change, -783 cal/mole $(31.0^{\circ}C)$. 2. The dissolution rates of the two polymorphs of sulpiride containing polyethylene glycol 4000 were significantly diefferent in 0.01N HCl but the effect of polyethylene glycol on the dissolution rates of two polymorphs was not significant at low concentration of polyethylene glycol 4000. The study on the effect by stirring speed showed that at lower stirring speed the promotion rate of dissolution of polymorph form I is greater than that of form II. 3. In the case of tablets the dissolution rates of polymorph form I of sulpiride was two fold as compared with the results obtained from form II.

  • PDF

니켈기 초내열 합금의 천이액상확산접합 특성에 미치는 접합 온도 및 가열 속도의 영향 (Effect of Bonding Temperature and Heating Rate on Transient Liquid Phase Diffusion Bonding of Ni-Base Superalloy)

  • 최우혁;김성욱;김종현;김길영;이창희
    • Journal of Welding and Joining
    • /
    • 제23권2호
    • /
    • pp.52-58
    • /
    • 2005
  • This study was carried out to investigate the effect of bonding temperature and heating rate on transient liquid phase diffusion bonding of Ni-base superalloy. The heating rate was varied by $0.1^{\circ}C$/sec, $1^{\circ}C$/sec, $10^{\circ}C$/sec to the bonding temperatures $1100^{\circ}C,\;1150^{\circ}C,\;1200^{\circ}C$ under vacuum. As bonding temperature increased, maximum dissolution width of base metal increased, but a dissolution finishing time decreased. The eutectic width of insert metal in the bonded interlayer decreased linearly in proportion to the square root of holding time during isothermal solidification stage. The bonding temperature was raised, isothermal solidification rate slightly increased. As the heating rate decreased and the bonding temperature increased, the completion time of dissolution after reaching bonding temperature decreased. When the heating rate was very slow, the solidification proceeded before reaching bonding temperature and the time required for the completion of isothermal solidification became reduced.

아세트아미노펜 좌제의 용출과 직장흡수 (Dissoultion and Rectal Absorption of Acetaminophen from Suppositories)

  • 한정선;심창구;김신근
    • 약학회지
    • /
    • 제31권5호
    • /
    • pp.286-295
    • /
    • 1987
  • The relationship between in vitro release and in vivo bioavailability of acetaminophen from suppositories was investigated. Effect of glycyrrhizin on the drug release and rectal absorption in rats was also examined. Suppositories containing 25mg of acetaminophen were prepared with Wecobee FS (fatty base) or PEG (water-soluble base) bases. The release from the suppositories were determined with USP rotating basket dissolution apparatus and with the suppository release tester. The temperature of the dissolution medium was very critical for the dissolution of acetaminophen from Wecobee FS suppositories. The bioavailability of acetaminophen was calculated from the plasma concentration-time curve after rectal administration of the suppositories to the rats. There were no significant differences in AUC following rectal administration of Wecobee FS and PEG suppositories, but the release and absorption from the Wecobee FS suppositories were faster than those from PEG suppositories. The dissolution rate obtained by the suppository release tester was better correlated with in vivo absorption rate constant than that by the USP dissolution apparatus. It suggests that the partitioning between rectal fluid and suppository base is the rate-limiting step in the rectal absorption of acetaminophen from suppositories. Glycyrrhizin was found not to affect in vitro dissolution and rectal absorption of acetaminophen.

  • PDF

질산용액에 UO2 Pellet의 용해특성에 관한 연구 (A Study on Dissolution Characteristics of UO2 Pellet in Nitric Acid)

  • 정원명;박진호;이규일;유재형;정경채
    • 공업화학
    • /
    • 제9권3호
    • /
    • pp.388-393
    • /
    • 1998
  • 의료용 동위원소인 fission Mo($^{99}Mo$)를 제조하기 위한 공정중 $UO_2$ 표적의 질산용해공정의 조업조건을 확립하기 위하여 $UO_2$ pellet의 유효표면적($s:0.034{\sim}0.282cm^2/g-UO_2$), 질산농도(1.5~10N), 반응온도 ($40{\sim}105^{\circ}C$)에 따른 $HNO_3$ pellet의 용해특성을 확인하였다. 그 결과 용해속도가 $UO_2$ pellet의 유효표면적에 정비례하며 표면적이 클수록 그 경향이 뚜렸함을 확인하였고, 반응속도와의 관계가 dc/dt = 10.6s로 나타났다. 용해속도와 질산농도와의 관계는 일정온도($90^{\circ}C$)에서 [$HNO_3$]1.42에 비례하는 것으로 나타났고, 온도변화에 따른 관계는 $90^{\circ}C$까지는 온도가 증가함에 따라 용해속도가 급격히 증가하나 그 이상에서는 오히려 감소하는 것으로 나타났으며, 활성화 에너지가 36.3KJ/mol로 계산되었다.

  • PDF

Al-SiCp복합재료에서 SiCp의 용해거동에 관한 연구 (A Study on Dissolution Behaviors of SiCp in Al-SiCp Composite)

  • 김석원;이의권;전우용
    • 한국주조공학회지
    • /
    • 제13권4호
    • /
    • pp.350-358
    • /
    • 1993
  • Aluminum base composites reinforced with various amount of SiC particles and Mg contents have been investigated by different fabrication method for twenty-years. In this paper, how the decomposition and dissolution behaviors of $SiCp(20{\mu}m)$ in the melt of Al composites arised was studied. As the results, the decomposition and dissolution of SiCp into the melt of Al composites increased with increase of the temperature above $720^{\circ}C$, and holding time at a given melting temperature. Because SiC is thermodynamically unstable in this Al-SiCp composite at temperature above the liquidus, SiCp dissolves and reacts with Al in matrix to form $Al_4C_3$ according to following chemical equation $4Al+3SiC{\rightarrow}Al_4C_3+3Si$, Si decomposed and dissolved from SiCp increases Si content of matrix, while liquidus temperature of matrix decrease with increase of SiC content in matrix. The hardness of SiCp decreased with increase of the melting temperature, the hardness of the matrix /particle interface increased with increase of the melting temperature due to increase of the $Mg_2Si$ and $Al_4C_3$ intermetallic compounds, etc.

  • PDF