• Journal of Integrative Natural Science
• /
• v.7 no.2
• /
• pp.130-137
• /
• 2014

Resins were synthesized by mixing N-phenylaza-15-crown-5 macrocyclic ligand attached to styrene (2th petroleum in 4th class hazardous materials) divinylbenzene (DVB) copolymer with crosslink of 1%, 2%, 6%, and 12% by substitution reaction. The synthesis of these resins was confirmed by content of chlorine, element analysis, thermo gravimetric analysis (TGA), surface area, and IR-spectroscopy. The effects of pH, equilibrium arrival time, dielectric constant of solvent and crosslink on adsorption of metal ions by the synthetic resin adsorbent were investigated. The metal ions were showed fast adsorption on the resins above pH 4. The optimum equilibrium time for adsorption of metallic ions was about two hours. The adsorption selectivity determined in ethanol was in increasing order uranium (VI) > zinc (II) > europium (III) ions. The uranium ion adsorbed in the order of 1%, 2%, 6%, and 12% crosslink resin and adsorption of resin decreased in proportion to the order of dielectric constant of solvents.

• Korean Journal of Soil Science and Fertilizer
• /
• v.33 no.1
• /
• pp.32-39
• /
• 2000

To investigate the adsorption-desorption reaction of Cd by sewage sludge, the adsorption of Cd from $Cd(NO_3)_2$ solutions of concentrations ranging from 5 to $50{\mu}g\;Cd\;mL^{-1}$ by sewage sludge was examined for reaction periods up to 48 hours. The amount of Cd adsorbed as a function of time was measured. The adsorption between Cd in solution and the solid phase could be described by two stages. The initial adsorption of Cd was very rapid, that is, approximately 95% of the added Cd was removed from solution within the first 30 minutes. Further, the greater the concentration of Cd added, the greater was the amount of Cd adsorbed. After the rapid initial decrease of Cd, a slower decline in the Cd concentration resulted which followed first order reversible kinetics. The equilibrium concentrations for the reactions, as well as the time period for the equilibrium reactions were dependent on the initial Cd concentrations. If equilibrium is reached, the amount of Cd remaining in solution is greater when the amount adsorbed is higher, although the percentage of Cd in solution is constant relative to the initial concentration of Cd. Some of the adsorbed Cd was released back to solution since the concentration of Cd after 48 hours was higher than the equilibrium concentration of Cd. However, despite the increased amount of Cd measured, the overall net reaction was a significant adsorption of Cd from solution by sewage sludge.

• Journal of Korean Society on Water Environment
• /
• v.22 no.3
• /
• pp.498-503
• /
• 2006

Adsorption features of $Cd^{2+}$ on waste tire particles have been investigated for the purpose of enhanced wastes recycling along with the development of an economic process for wastewater treatment. The isoelectric point of waste tire particles was found to be ca. pH 7 and the adsorbed amount of $Cd^{2+}$ was increased with pH under experimental conditions. The variation of the adsorption behavior of $Cd^{2+}$ with pH was well explained by the change of the electrokinetic potential of waste tire particles according to the pH. Adsorption of $Cd^{2+}$ was observed to reach its equilibrium within 45 minutes after the adsorption started under experimental conditions and followed the Freundlich model well. Kinetic analysis showed that the adsorption reaction of $Cd^{2+}$ was second order and thermodynamic estimation substantiated the endothermic behavior of $Cd^{2+}$ adsorption. As the amount of adsorbent increased, more adsorption of $Cd^{2+}$ was accomplished and the adsorption capacity of adsorbent was found to be enhanced by its pre-treatment with NaOH. Also, the adsorption of adsorbate was promoted as the ionic strength of wastewater was increased.

• Journal of the Korean Applied Science and Technology
• /
• v.13 no.3
• /
• pp.25-34
• /
• 1996

We have synthesized the water-insoluble chitosan derivative, N-dithiocarboxy chitosan sodium salt, through the reaction of chitosan with carbon disulfide in the presence of alkali metal hydroxide, Chitosan itself has been prepared using chitin, one of the most abundant compounds in nature, as a starting material. To elucidate this natural polymer the capacity of adsorbing heavy metal ions, we have performed adsorption experiments using chitosan derivatives of various average molecular weights with different contents of sulfur. The effect of pH, adsorption time and temperature on adsorption efficiency was also studied. The adsorbent derived from chitosan of average molecular weight ranging $5,700{\sim}20,000$ was shown to have the highest capacity of adsorbing heavy metal ions. Adsorbing efficiency was increased as the reaction time was increased and as the reaction temperature range of $25{\sim}45^{\circ}C$. The adsorption capacity at various pH, however, appeared to vary depending on the heavy metal ions studied.

• Journal of the Korean Applied Science and Technology
• /
• v.13 no.2
• /
• pp.85-92
• /
• 1996

Chitosan itself has been prepared using chitin, one of the most abundant compounds in nature, as a starting material. We have synthesized the water-soluble chitosan derivative, N-dithiocarboxy chitosan sodium salt, through the reaction of water-soluble chitosan with carbon disulfide in the presence of alkali metal hydroxide. To elucidate this natural polymer capacity of adsorbing heavy metal ions, we have performed adsorption experiments using the water-soluble chitosan derivative various average molecular weight and of different percent contents of sulfur. The effect of pH, adsorption time and temperature on adsorption efficiency was also studied. The adsorbent derived from water-soluble chitosan of average molecular weight ranging $9,000{\sim}120,000$ was shown to have the highest capacity of adsorbing heavy metal ions. On the whole, adsorbing efficiency was increased as the reaction time goes longer and also increased as the reaction temperture goes higer in temperture range of $15^{\circ}C{\sim}45^{\circ}C$. The adsorption capacity at various pH, however, was appeared to vary depending on the heavy metal ions studied Judging from these finding, water-soluble N-dithiocarboxy chitosan sodium salt, a derivative of a biodegradable nature polymer, is believed to be a potential adsorbent for heavy metal ions since it not only is shown to lower the concentration of heavy metal ions to below the drainage quality standard, but also it would not cause acidification and hardening of soil which is one of the detrimental effects of synthetic macromolecular adsorbents present.

• Korean Chemical Engineering Research
• /
• v.61 no.4
• /
• pp.598-603
• /
• 2023

Electrochemical ammonia production using catalysts offers a promising alternative to the conventional Haber-Bosch process, allowing for ambient temperature and pressure conditions, environmentally friendly operations, and high-purity ammonia production. In this study, we focus on the nitrogen reduction reactions occurring on the surfaces of ruthenium catalysts, employing first-principles calculations. By modeling reaction pathways for nitrogen reduction on the (0001) and (1000) surfaces of ruthenium, we optimized the reaction structures and predicted favorable pathways for each step. We found that the adsorption configuration of N₂ on each surface significantly influenced subsequent reaction activities. On the (0001) surface of ruthenium, the end-on configuration, where nitrogen molecules adsorb perpendicularly to the surface, exhibited the most favorable N₂ adsorption energy. Similarly, on the (1000) surface, the end-on configuration showed the most stable adsorption energy values. Subsequently, through optimized hydrogen adsorption in both distal and alternating configurations, we theoretically elucidated the complete reaction pathways required for the final desorption of NH₃.

• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.565-573
• /
• 2021

Isotherms, kinetics and thermodynamic properties for adsorption of Brilliant Green(BG), Quinoline Yellow(QY) dyes by activated carbon were carried out using variables such as dose of adsorbent, pH, initial concentration, contact time, temperature and competitive. BG showed the highest adsorption rate of 92.4% at pH 11, and QY was adsorbed at 90.9% at pH 3. BG was in good agreement with the Freundlich isothermal model, and QY was well matched with Langmuir model. The separation coefficients of isotherm model indicated that these dyes could be effectively treated by activated carbon. Estimated adsorption energy by Temkin isotherm model indicated that the adsorption of BG and QY by activated carbon is a physical adsorption. The kinetic experimental results showed that the pseudo second order model had a better fit than the pseudo first order model with a smaller in the equilibrium adsorption amount. It was confirmed that surface diffusion was a rate controlling step by the intraparticle diffusion model. The activation energy and enthalpy change of the adsorption process indicated that the adsorption process was a relatively easy endothermic reaction. The entropy change indicated that the disorder of the adsorption system increased as the adsorption of BG and QY dyes to activated carbon proceeded. Gibbs free energy was found that the adsorption reaction became more spontaneous with increasing temperature. As a result of competitive adsorption of the mixed solution, it was found that QY was disturbed by BG and the adsorption reduced.

• Journal of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.226-232
• /
• 1991

Adsorption and oxidation of polychlorinated phenols by suspended ${\sigma}-MnO_2$ in aqueous solution have been studied. Of the proposed mechanism, adsorption reaction of chlorophenols onto ${\sigma}-MnO_2$(s) depended upon the pH of the solution and the concentration of chlorophenol. Adsorption isotherms showed a reasonably good fit to the Langmuir isotherm. From the pH dependence of adsorption partition coefficient and the linear relationship between octanol-water partition coefficient and adsorption partiton coefficient of chlorophenol, it is estimated that adsorption is dominated by its hydrophobicity. The rate of electron transfer reaction evaluated from the rate of reductive dissolution of ${\sigma}-MnO_2$(s) depended linearly upon the concentration of chlorophenol and the pH of medium. Observed rate constants ($K_0$) of the meta-substituted chlorophenol were lower than that of the ortho-or para-chlorophenol because of resonance effect of chlorophenoxy radical. It is indicated that this radical is produced in the adsorption process and the electron transfer reaction is rate determining.

• Journal of the Korean Geosynthetics Society
• /
• v.13 no.2
• /
• pp.59-67
• /
• 2014

The amount of the contaminants that can be adsorbed on the drain was evaluated for the effective remediation of the contaminated soil, and the contaminants adsorptivity of the drain was evaluated by comparing the isothermal adsorption model after carrying out the contaminants adsorption test of the reactants coated on the surface of the drain. The reactant used in the experiment is a natural zeolite, and the contaminants are copper, lead and cadmium. The results that Freundlich and Langmuir adsorption isotherm model are compared to the adsorption amount according to the change of the initial concentration by the contaminants. As a result of the component analysis, because Si, Al and O are contained approximately 28%, 11% and 48%, respectively, it is identified that the material coated on the surface of the drain is the component of the zeolite which is the reactant for the adsorption of the heavy-metal (Cu, Pb, Cd) contaminants. The heavy-metal adsorption kinetic of the zeolite which is the reactant was decreased in order of lead, copper and cadmium. The important factor of the performance evaluation of the adsorbent is the reaction rate, and if zeolite is used as the reactant in the relationship between the maximum amount of adsorption and reaction rate, it can be utilized as the design factor that determine the removal order of the complex heavy-metal. In other words, because the maximum adsorption quantity of lead is smaller compared to copper but the reaction rate is relatively fast, it can be primarily removed, and copper can be removed after removing the lead. It was analyzed that Cadmium can be finally removed after that other heavy-metal is removed.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.5
• /
• pp.242-248
• /
• 2016

The overall reaction rate of fuel cell is governed by oxygen reduction reaction (ORR) in the cathode due to its slowest reaction compared to the oxidation of hydrogen in the anode. The ORR efficiency can be readily evaluated by examining the adsorption strength of atomic oxygen on the surface of catalysts (i.e., known as a descriptor) and the adsorption energy can be controlled by transforming the surface geometry of catalysts. In the current study, the effect of the surface geometry of catalysts (i.e., strain effect) on the adsorption strength of atomic oxygen on platinum catalysts was analyzed by using density functional theory (DFT). The optimized lattice constant of Pt ($3.977{\AA}$) was increased and decreased by 1% to apply tensile and compressive strain to the Pt surface. Then the oxygen adsorption strengths on the modified Pt surfaces were compared and the electron charge density of the O-adsorbed Pt surfaces was analyzed. As the interatomic distance increased, the oxygen adsorption strength became stronger and the d-band center of the Pt surface atoms was shifted toward the Fermi level, implying that anti-bonding orbitals were shifted to the conduction band from the valence band (i.e., the anti-bonding between O and Pt was less likely formed). Consequently, enhanced ORR efficiency may be expected if the surface Pt-Pt distance can be reduced by approximately 2~4% compared to the pure Pt owing to the moderately controlled oxygen binding strength for improved ORR.