• Carbon letters
• /
• v.3 no.4
• /
• pp.219-225
• /
• 2002

The two-step surface modifications of activated carbon was carried out to improve the adsorption capacity of toxic heavy metal ions in liquid phase. Physical and chemical properties of the as-received activated carbon (AC) and two kinds of surface-modified activated carbons ($1^{st}AC$ and $2^{nd}AC$) were evaluated through the BET analysis, surface acidity, and oxides measurements. Specific surface area and pore volume did not significantly change, but surface oxide-group remarkably increased by the surface modification. Equilibrium and batch adsorptions of the various metals, such as Pb, Cd, and Cr, using AC, $1^{st}AC$, and $2^{nd}AC$ were performed at initial pH 5. The adsorption capacity and rate of $2^{nd}AC$ were higher than those of AC and $1^{st}AC$. The carboxylic/sodium carboxylate complex groups were developed from the two-step surface modification of activated carbon, which strongly affected the adsorption of metal ions.

• Carbon letters
• /
• v.5 no.4
• /
• pp.170-179
• /
• 2004

The equilibrium and dynamic adsorption of methylene blue from aqueous solutions by activated carbons have been studied. The equilibrium studies have been carried out on two samples of activated carbon fibres and two samples of granulated activated carbons. These activated carbons have different BET surface areas and are associated with varying amounts of carbon oxygen surface groups. The amounts of these surface groups was enhanced by oxidation with $HNO_3$ and $O_2$ gas at $350^{\circ}C$ and decreased by degassing at increasing temperatures of $400^{\circ}$, $650^{\circ}$ and $950^{\circ}C$. The adsorption increases on oxidation of the carbon surface and decreases on degassing. The increase in adsorption has been attributed to the formation of acidic carbon-oxygen surface groups and the decrease in adsorption on degassing to their elimination. The dynamic adsorption studies have been carried out on the two granulated activated carbons using two 50 mm diameter glass columns at a feed concentration of 300 mg/L and at different hydraulic loading rates (HLR) and bed heights. The minimum achievable concentrations are comparatively lower while the adsorption capacities are higher for GAC-S under the same operating conditions. The adsorption capacity of a carbon increases with increase in HLR but the rate of increase decreases at higher HLR values.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.1
• /
• pp.1-8
• /
• 2005

An axisymmetric compressible flow solver accounting for chemical equilibrium has been developed as an analysis tool exclusively suitable for performance prediction and optimum contour design of LRE thrust chamber. By virtue of several features focusing on user-friendliness and effectiveness including automatical grid generation and iterative calculations with changes in design parameters prescribed through only one keyword-type input file, a design engineer can evaluate very fast and easily the influences of various design inputs such as geometrical parameters and operating conditions on propulsive performance. Validations have been carried out for various aspects by detailed comparisons with the result of CEA code, experimental data of JPL nozzle, actual data for two historical engines, and ReTF data for KSR-III.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.03a
• /
• pp.146-153
• /
• 2004

The Numerical study has been carried out to investigate the effects of chemical reaction and thermal radiation on the rocket plume flow-field at various altitudes. The theoretical formulation is based on the Navier-Stokes equations for compressible flows along with the infinitely fast chemistry and thermal radiation. The governing equations were solved by a finite volume fully-implicit TVD(Total Variation Diminishing) code which uses Roe's approximate Riemann solver and MUSCL(Monotone Upstream-centered Schemes for Conservation Laws) scheme. LU-SGS (Lower Upper Symmetric Gauss Seidel) method is used for the implicit solution strategy. An equilibrium chemistry module for hydrocarbon mixture with detailed thermo-chemical properties and a thermal radiation module for optically thin media were incorporated with the fluid dynamics code. In this study, kerosene-fueled rocket was assumed operating at O/F ratio of 2.34 with a nozzle expansion ratio of 6.14. Flight conditions considered were Mach number zero at ground level, Mach number 1.16 at altitude 5.06km and Mach number 2.9 at altitude 17.34km. Numerical results gave the understandings on the detailed plume structures at different altitude conditions. The diffusive effect of the thermal radiation on temperature field and the effect of chemical recombination during the expansion process could be also understood. By comparing the results from frozen flow and infinitely fast chemistry assumptions, the excess temperature of the exhaust gas resulting from the chemical recombination seems to be significant and cannot be neglected in the view point of performance, thermal protection and flow physics.

• Journal of The Korean Association For Science Education
• /
• v.18 no.3
• /
• pp.303-312
• /
• 1998

In this study, the multimedia CAl program for chemical equilibrium in high school grade 3 was developed and the effect of CAl on achievement and attitude toward chemistry instruction and computer was investigated. Before instruction, the test of attitudes toward chemistry instruction and computer were administered, and the grade in the mid-term examination was obtained. These scores were used as covariates. Mid-term science score was used as blocking variable. For chemical equilibrium instruction, traditional and computer assisted instruction were used. After instruction, the achievement test and the test of attitudes toward science instruction and computer were administered. The results indicated that students in the treatment group achieved significantly better than those in the control group, but did not show improvement of attitude to chemistry instruction and computer compared to those in the control group. No significant interaction between the treatment and the level of students' prior achievement was found. Female achieved significantly better under CAl than under traditional instruction. In two subtests(understanding and application), treatment group achieved better in the subtest of application than control group. CAl had an effect on chemical equilibrium state (about reversibility) significantly. While female of the treatment group did not show more positive attitude toward both chemistry instruction and computer significantly than that of the control group, male showed more positive attitude significantly. Educational implications are discussed.

• Environmental Engineering Research
• /
• v.22 no.4
• /
• pp.384-392
• /
• 2017

Mango shell (MS) and mango shell activated carbon (MSAC) was used to adsorb crude oil from water at various experimental conditions. The MSAC was prepared by carbonization at $450^{\circ}C$ and chemical activation using strong $H_3PO_4$ acid. The adsorbents were characterized with Fourier Transform Infrared spectroscopy. Investigations carried out included the effects of parametric variations of different adsorbate dose, adsorbent dose, time, temperature, pH and mixing speed on the adsorption of crude oil. The equilibrium isotherm for the adsorption process was determined using Langmuir, Freundlich, Temkin and Dubinin Radushkevich isotherm models. Temkin isotherm was found to fit the equilibrium data reasonably well than others. The result demonstrated that MSAC was more effective for crude oil adsorption than raw mango shell. Optimum conditions were also presented. The enhanced effect from activation was justified statistically using Analysis of Variance and Bonferroni-Holm Posthoc significance test. The pseudo first order kinetics gave a better fit for crude oil adsorption with both MS and MSAC.

• Carbon letters
• /
• v.9 no.2
• /
• pp.97-104
• /
• 2008

In the present study Sisal fiber obtained from the leaves of Agave sisalana has been chosen to validate its viability as an adsorbent for the removal of Nickel from aqueous solutions. The material was also surface modified and its effect on adsorption of Nickel was also studied. Agave sisalana fiber was found to be a cheap and effective adsorbent doing away with the need to activate the material therby reducing processing cost. The equilibrium studies indicated that the adsorption capacity of raw fiber and the surface modified fiber was 8.66 and 9.77 mg/g respectively with the Langmuir isotherm describing the adsorption phenomena better than the Freundlich and Temkin isotherm. The adsorption was found to be exothermic from the thermodynamic studies and the kinetics showed that the adsorption phenomena were second order.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.6 no.5
• /
• pp.347-351
• /
• 2001

A study was made on the extraction equilibria of succinic and formic acids from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol. It was shown that the loading values of TOA decreased with increasing pH values. The apparent equilibrium constants for each acidamine complex were determined by an equilibrium model. In the case succinic acid, the formation of a bisuccinate anion played an important role in the stoichiometry of the acid-amine complex.

• Journal of Microbiology and Biotechnology
• /
• v.11 no.5
• /
• pp.781-787
• /
• 2001

The binding of heavy metals by a biosorbent with binary functional groups was mathematically modeled. An FT-IR spectrophotometer analysis was employed to determine the stoichiometry between the protons in the functional groups of alginic acid and lead ions as a model system. The results calculated using an equilibrium constant agreed well with the experimental results obtained under various operating conditions, such as pH and metal ion concentration. It was also shown that the overall adsorption phenomenon of alginic acid was mainly due to its carboxyl groups. The equilibrium constants for each functional group successfully predicted the lead adsorption of ${\alpha}$-cellulose. Furthermore, the biosorption model could predict the adsorption phenomena of two metal ions, lead ions and calcium ions, relatively.

• Macromolecular Research
• /
• v.11 no.1
• /
• pp.53-61
• /
• 2003

A molecular-thermodynamic model is developed for the salt-induced protein precipitation. The protein molecules interact through four intermolecular potentials. An equation of state is derived based on the statistical mechanical perturbation theory with the modified Chiew's equation for the fluid phase, Young's equation for the solid phase as the reference system and a perturbation based on the protein-protein effective two body potential. The equation of state provides an expression for the chemical potential of the protein. In a single protein system, the phase separation is represented by fluid-fluid equilibria. The precipitation behaviors are simulated with the partition coefficient at various salt concentrations and degree of pre-aggregation effect for the protein particles. In a binary protein system, we regard the system as a fluid-solid phase equilibrium. At equilibrium, we compute the reduced osmotic pressure-composition diagram in the diverse protein size difference and salt concentrations.