• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.322-327
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• 2023

A design of experiments was evaluated in optimizing MOF-5 synthesis for acetylene adsorption. At first, mixture design was used to optimize precursor concentration, terephthalic acid, zinc acetate dihydrate and N,N-dimethylformamide. More specifically, 13 conditions with various molar ratios were designed by extreme vertices design method. After preparing the samples, XRD, N₂ physisorption and SEM analysis were performed for their characterization. Moreover, acetylene adsorption experiments were carried out over the samples under identical conditions. The optimal precursor composition for MOF-5 synthesis was predicted on a molar basis as follows: terephthalic acid : acetate dihydrate : dimethylformamide = 0.1 : 0.4 : 0.5. Thereafter, multi-level factorial design was designated to investigate the effect of synthesis reaction conditions such as temperature, time and stirring speed. By the statistical analysis of 18 samples designed, 4 reaction parameters were determined for additional adsorption experiments. Therefore, MOF-5 prepared under the synthesis time and temperature of 100 ℃ and 12 h, respectively, showed the maximum adsorption capacity of 15.1 mmol/g.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.327-332
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• 2013

Batch experiments were carried out for adsorption equilibrium, kinetics and thermodynamic parameters of the brilliant brown R onto granular activated carbon. The operating variables studied were the initial dye concentration, contact time and temperature. Experimental equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption isotherm by linear regression method. The equilibrium process was well described by Freundlich isotherm model and from the determined separation factor (1/n), granular activated carbon could be employed as an effective treatment for the removal of bismarck brown R. From kinetic experiments, the adsorption processes were found to confirm the pseudo second order model with a good correlation and the adsorption rate constant ($k_2$) increased with increasing adsorption temperature. Thermodynamic parameters like the activation energy, change of Gibbs free energy, enthalpy, and entropy were also calculated to predict the nature of adsorption in the temperature range of 298~318 K. The activation energy was determined as 8.73 kJ/mol for 100 mg/L. It was found that the adsorption of bismarck brown R on the granular activated carbon was physical process. The negative Gibbs free energy change (${\Delta}G$ = -2.59~-4.92 kJ/mol) and the positive enthalpy change (${\Delta}H$ = +26.34 kJ/mol) are indicative of the spontaneous and endothermic nature of the adsorption process.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.141-149
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• 2014

In the present study, pure RHO zeolite was hydrothermally synthesized by using 18-crown-6 ether as a structure directing agent(SDA), and the small gases adsorption was investigated. Synthesized RHO zeolite was a cube shape particle of which average edge length was around $1.2{\mu}m$ and composed of primary crystallites having a diameter of around 100 to 200 nm. RHO zeolite structure was stable under 3h calcination at $600^{\circ}C$. Water adsorption data announced that RHO zeolite has a specific surface area of 483.32 m2/g and its micropore diameter was about 4 A. Gas adsorption was studied in the pressure range of 50 to 500 kPa for $CO_2$, $N_2$, $O_2$ and $H_2$. It was evident that RHO zeolite showed a strong $CO_2$ adsorption behavior. Especially, RHO zeolite showed a transient $CO_2$ adsorption behavior. The 3h $CO_2$ up-take at 50 kPa and 500 kPa was 1.283 and 3.357 mmol/g, respectively. The $CO_2/H_2$ selectivity was around 16 at 500 kPa. Compared with gas adsorption data for some representative microporous adsorbents, it was certain that RHO zeolite is a beneficial adsorbent for $CO_2/H_2$ separation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.215-215
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• 2011

The bonding configuration and adsorption stability of alanine and leucine adsorbed on Ge(100)-2${\times}$1 surface were investigated and compared using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The bonding configuration, stability, and adsorption energies were evaluated for two different coverage levels. In both cases, the C 1s, N 1s, and O 1s core-level spectra at a low coverage (0.30 ML) indicated that the carboxyl and amine groups participated in bonding with the Ge(100) surface in an "O-H dissociated-N dative bonded structure". At high coverage levels (0.60 ML), both this structure and an "O-H dissociation bonded structure" were present. As a result, we found that alanine adsorbs more easily (lower adsorption energy) than leucine on Ge(100) surfaces due to less steric hindrance of side chain.

• Journal of Environmental Science International
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• v.2 no.4
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• pp.357-365
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• 1993

This study was conducted for the efficient utilization of biomaterials such as starch residue, tangerine skin, and green tea residue, which are agricultral by-products discarded in Cheju Province annually, as adsorbents and biomaterials were examined for their removal ability of heavy metal ions in waste water by batch adsorption experiments. The removal efficiency of biomaterials for heavy metal ions was above 80-90% and almost similar to activated carbon and the adsorption ability of those treated with 포르말린 was improved in the green tea residue only for $Pb^{2+}$, $Cu^{2+}$, and $Zn^{2+}$. In the conditions of pH, the removal efficiency of heavy metal ions was high in the range of 5-7. In the solutions which heavy metal ions were mixed, the removal efficiency was similar at $Ag^+$, $Pb^{+2}$ and reduced to about 10% at the other ions, as compared with the solutions they were not mixed. Adsorption isotherm of biomaterials was generally obeyed to Freundlich formular than Langmuir formular and Freundlich constant, 1/n were obtained in the range of 0.1-0.5.

• Journal of environmental and Sanitary engineering
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• v.19 no.1
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• pp.37-41
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• 2004

The removal efficiency of cadmium by chitosan complex isolated from Aspersillus oryzae was investigated through laboratory experiments. The results of the study are as follows. The adsorption kinetics of cadmium was reached the adsorption equilibrium in approximately 20 minutes and the removal efficiency was showed 95.8%. The effect of temperature on cadmium adsorption by chitosan complex shows that as the temperature increased, the amount of cadmium adsorption per unit weight of chitosan complex increased. The correlation between amount of cadmium adsorption per unit weight of chitosan complex and temperature was obtained through the coefficient of determination($R^2$). $R^2$ values was 0.854(p<0.05). A linearized Freundlich equation was used to fit the acquired experimental data. As a result, Freundlich constant, the adsorption intensity(1/n) was 0.550, and the measure of adsorption(k) was 2.181. So, it was concluded that adsorption of cadmium by chitosan complex is effective.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.204-210
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• 1991

Multilayer adsorption isotherms of nitrogen and argon on the perovskite-type mixed oxides, synthesized by a citrate coprecipitation method, are determined at the liquid nitrogen temperature using a gravimetric adsorption apparatus. The volume of the adsorbed gas are plotted against the statistical thickness of the adsorbed layer, calculated from several universal adsorption isotherms one after another. The t-method area obtained from this plot is compared with the BET area and finally the appropriateness of universal adsorption isotherms is then discussed on the basis of the plot.

• Journal of Environmental Health Sciences
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• v.27 no.1
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• pp.93-99
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• 2001

This study aims at finding out pertinent reaction conditions for treating high concentration ammonia contained in N-chemical factory wastewater with decompressed ammonia stripping method that was designed. And it also tries to investigate adsorption capability of removed ammonia to soil. The results from experiments are as follows ; 1. The removal rate of N $H_3$-N of synthetic wastewater was under 85% at pH 10 with decompressed ammonia stripping method. The reaction time in pressure 360 mmHg at pH 11 and 12 was shorter than in 460 mmHg, and the removal rate of N $H_3$-N with decompressed ammonia stripping method at 9$0^{\circ}C$ was 11~15% higher than air stripping 2. The optimum conditions for decompressed ammonia stripping with synthetic sample were shown as pH 12, temperature 9$0^{\circ}C$, internal reaction pressure 460 mmHg and reaction time 50 minutes. These conditions were applied to treat the wastewater containing organic-N 290.5mg/$\ell$, N $H_3$-N 168.9mg/$\ell$, N $O_2$-N 23.2mg/$\ell$, N $O_3$-N 252.4mg/$\ell$, T-N 735mg/$\ell$. Organic-N turned out to be removed 60%, the removal rate of N $H_3$-N IS 94%, T-N is 50%. But N $O_2$-N and N $O_3$-N were increased with 7.8% and 14.9% respectively. 3. The CO $D_{Sr}$ removal rate in decompressed ammonia stripping reaction was 42% and S $O_4$$^{2-}$ was removed 8.2%. It was turned out caused with higher pH and thermolysis. 4. In soil adsorption of ammonia desorbed from the decompressed stripping process of wastewater, the recovery rate was 76% in wet soil.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.255-261
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• 2016

Adsorption experiments of Acid Yellow 14 dye using activated carbon were carried out as function of adsorbent dose, pH, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherm model. The experimental data were best represented by Freundlich isotherm model. Base on the estimated Freundlich constant (1/n=0.129~0.212) and Langmuir separation factor ($R_L=0.202{\sim}0.243$), this process could be employed as effective treatment method. The heat of adsorption of Temkin isotherm model was 5.101~9.164 J/mol indicated that the adsorption process followed a physical adsorption. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy (-4.81~-10.33 kJ/mol) and positive enthalpy (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• Membrane Journal
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• v.29 no.5
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• pp.237-245
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• 2019

Ammonia nitrogen is well known as a substance that causes the eutrophication with a phosphorus in the water, because it is contained in the industrial wastewater, agricultural and the stockbreeding wastewater. In addition, manganese (Mn) and arsenic (As) are included in the mine treated water, etc., and are known as a source of water pollution. Natural zeolites are used to remove ammonia nitrogen in water but it have a low adsorption capacity. In order to improve the low adsorption capacity of the natural zeolite, ion substitution was carried out with $Na^+$, $Ca^{2+}$, $K^+$ and $Mg^{2+}$. The adsorption capacity and removal rate of ammonia nitrogen ($NH_4-N$) were the highest at 0.66 mg/g and 89.8% in $Na^+$ ion exchanged zeolite. Adsorption experiments of Mn and As were performed using ion exchanged zeolites. Ion exchanged zeolite with $Mg^{2+}$ showed high adsorption capacity and removal rates of Mn and As.