• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.339-349
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• 2015

In this work, DAY (Dealuminated Y-type) zeolites were prepared to be used as easily regenerable and thermally stable adsorbent substituting activated carbon. NaY zeolites were transformed into DAY zeolites through ion exchange, calcination, steaming, and acid leaching. Calcination temperature and time, and steaming time were changed to increase the Si/Al ratio and maintain crystallinity. Adsorption of VOCs were done for prepared DAY, commercial NaY and Hisiv 1000 in air with relative humidity of 50%. The DAY zeolite prepared by calcination at $520^{\circ}C$ for 4 hrs and steaming for 7 hrs had a same structure and a Si/Al ratio of 80.4. Its adsorption capacity for water vapor was 10% of NaY, indicating its hydrophobicity. Its adsorption capacity for MEK was 0.8 times of Hisiv 1000, that for toluene 1.6 times, and that for EA 1.3 times.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.149-154
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• 2012

The adsorption and desorption behavior of biofilter-medium was investigated on the performance of an adsorption column. Continuous flow-isothermal adsorption experiments were performed to treat waste air containing such a VOC as ethanol under the same condition of > 90% relative humidity as the condition of the feed to a biofilter process. In case of feeding waste air containing ethanol of 1,000 ppmv (or 2,050 mg ethanol/$m^3$) to the adsorption system at the rate of 2 L/min, the onsets of its breakthrough and reaching the state of dynamic equilibrium at the exit had been delayed 10 and 3 times, respectively, later than those at the 1st stage sampling port. Moreover, in case of 2,000 ppmv (or 4,100 mg ethanol/$m^3$), they had been delayed 9 and 3 times, respectively. Thus, regardless of feeding concentration, the ratios of delaying period were observed to be quite consistent each other at the exit of the adsorption column. With regard to the period of desorption, the ratios of delaying period were consistent each other to be 1.5 for both cases. In addition, the effect of microbial activity and sterilization-process was studied on adsorption equilibrium. The ethanol concentration in the vapor phase of vials packed with sterilized granular activated carbon (GAC) was quite consistent to that with unsterilized GAC. However, the ethanol concentrations in the vapor phase of vials packed with unsterilized compost and the unsterilized mixture of GAC and compost were higher than those with sterilized compost and the sterilized mixture of GAC and compost, respectively.

• Carbon letters
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• v.22
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• pp.14-24
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• 2017

Carboxylated multi-wall carbon nanotubes (MWCNTs-COOH) have been used as efficient adsorbents for the removal of picric acid from aqueous solutions under stirring and ultrasound conditions. Batch experiments were conducted to study the influence of the different parameters such as pH, amount of adsorbents, contact time and concentration of picric acid on the adsorption process. The kinetic data were fitted with pseudo-first order, pseudo-second-order, Elovich and intra-particle diffusion models. The kinetic studies were well described by the pseudo-second-order kinetic model for both methods. In addition, the adsorption isotherms of picric acid from aqueous solutions on the MWCNTs were investigated using six two-parameter models (Langmuir, Freundlich, Tempkin, Halsey, Harkins-Jura, Fowler-Guggenheim), four three-parameter models (Redlich-Peterson, Khan, Radke-Prausnitz, and Toth), two four-parameter equations (Fritz-Schlunder and Baudu) and one five-parameter equation (Fritz-Schlunder). Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were applied to determine the best fit isotherm. The error analysis showed that the models with more than two parameters better described the picric acid sorption data compared to the two-parameter models. In particular, the Baudu equation provided the best model for the picric acid sorption data for both methods.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.521-527
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• 2017

Phosphorus is one of the limiting nutrients for the growth of phytoplankton and algae and is therefore one of leading causes of eutrophication. Most phosphorous in water is present in the form of phosphates. Different technologies have been applied for phosphate removal from wastewater, such as physical, chemical precipitation by using ferric, calcium or aluminum salts, biological, and adsorption. Adsorption is one of efficient method to remove phosphates in wastewater. To find the optimal media for phosphate removal, physical characteristics of media was analysed, and the phosphate removal efficiency of media (silica sand, slag, zeolite, activated carbon) was also investigated in this study. Silica sand showed highest relative density and wear rate, and phosphate removal efficiency. Silica sand removed about 36% of phosphate. To improve the phosphate removal efficiency of silica sand, Fe coating was conducted. Fe coated silica sand showed 3 times higher removal efficiency than non-coated one.

• Journal of Food Hygiene and Safety
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• v.14 no.1
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• pp.76-83
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• 1999

Solid phase microextraction (SPME) was used for the determination of 6 standard solvents (methanol, isopropanol, methyl ethyl ketone, ethyl acetate, cyclohexane, toluene) in food packaging materials. SPME method is a solvent-free sample preparation technique in which a fused silica fiber coated with polymeric organic liquid is introduced into the headspace above the sample. SPME method using fiber coated polydimethylisiloxane (PDMS) was compared with static headspace (SHS) method used as a reference. It was found that the optimal adsorption condition using PDMS-SPME method was 2$0^{\circ}C$ for 15 minutes for the standard solvents. Detection limits, linearity, reproducibility and recovery of both SHS and PDMS-SPME methods have been determined using 6 standard solvents. Both methods were characterized by high reproducibility and good linearity. Using SHS methods, the mean recovery of the 6 standard solvents was ranged from 75.5% to 105.8% with a mean relative standard deviation (RSD) of 0.3% to 4.8%. With PDMS-SPME method, the mean recovery of the 6 standard solvents was ranged from 86.7% to 108.3% with a mean RSD of 0.4% to 2.5%. The detection limits of both methods were the same for toluene, cyclohexane and methyl ethyl ketone; those of PDMS-SPME method were higher than those of SHS method for methanol, isopropanol and ethyl acetate. PDMS-SPME fiber shoed excellent adsorption for non-polar solvents such as toluene, while it showed relatively low adsorption for polar solvents such as methanol.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.84-89
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• 1996

The adsorption characteristics of active carbon used as a cartridge filler of organic vapor respirator were examined by humidity, particle size, challenge concentration and specific surface area. As a result, the 1% breakthrough time of Carbon Tetrachloride($CCl_4$) was decreased with increase of relative humidity, challenge concentration and particle size (0.6～2.0mm) of active carbon. The adsorbed amount of $CCl_4$ was about 1. 1mg/$m^2$ at RH 40% and 0. 5mg/$m^2$ at RH 80% . However in the case of prehumidified active carbon, humidity did not affected to 1% breakthrough time up to RH 40%.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.87-92
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• 2000

The electronic and chemical properties of the surface Pt and Ru atoms in the Pt-Ru alloy have been investigated by means of extended Huckel calculations. An electron transfer occurs from Ru to Pt, resulting in an increased electron density on the surface Pt atoms. The transfer is found to be larger toward Pt atoms out of contact with Ru. The calculated electronic perturbation of the water molecule is similar when it is adsorbed either on the Pt site or on the Ru site in the alloy. However, the water adsorption strength is much smaller in the former case, since the lone-pair donations are reduced relative to the latter case. This is essentially due to a larger closed-shell repulsive interaction between $1b_2(H_2O)$ and $d_{yz}$ (Pt).

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1085-1089
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• 2000

The effect of 2-hydroxyacetophenone-aroyl hydrazone derivatives on the inhibition of copper corrosion in 3N nitric acid solution at 303 K was investigated by galvanostatic polarization and thermometric techniques. A significant decrease in the cor rosion rate of copper was observed in the presence of the investigated compounds. The corrosion rate was found to depend on the nature and concentrations of the inhibitors. The degree of surface coverage of the adsorbed inhibitors is determined from polarization measurements, and it was found that the results obey the Frumkin adsorption isotherm. The inhibitors acted as mixed-type inhibitors, but the cathode is more polarized. The relative inhibitive efficiency of these compounds has been explained on the basis of structure dependent electron donor properties of the inhibitors and the nature of the metal-inhibitor interaction at the surface. Also, some thermodynamic data for the adsorption process ( ΔGa* and f ) are calculated and discussed.

• Clean Technology
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• v.25 no.3
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• pp.189-197
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• 2019

In this study an optimization of the preparation conditions of activated carbon with a ternary metal ion material to treat $H_2S$, which is classified as a representative odor substance, was carried out. For a metal ion material for enhancing the adsorption performance of hydrogen sulfide, performance enhancement was confirmed by combining Li and Fe or a ternary combination (K, Li, Fe) based on KI, which is a substance promoting hydrogen sulfide adsorption performance. Also, it was determined by XRD analysis that the reaction of each active substance with $H_2S$ was because of binding. The adsorption performance increased more than 3 times with heat treatment of the adsorbent with nitrogen compared with heat treatment with air. The maximum adsorption constant ($q_m$) value of the optimum adsorbent was 97.07, which is 6 times higher than that of the existing K-based impregnated activated carbon. It was confirmed that the objective adsorption amount ($0.3g\;g^{-1}$) was secured by an equilibrium between the mass transfer rate and adsorption rate. From the results, it was confirmed that the performance improvement was noticeable even when activated carbon with a reagent grade activated carbon particle size was modified. It was confirmed that the adsorption performance exists at high relative humidity levels of 60 and 100%, and the optimized preparation can be applied to a wet process such as a scrubber downstream.

• Food Science and Preservation
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• v.10 no.3
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• pp.297-301
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• 2003

The hardness of corrugated packaging box decreased during storage period because of high humidity. Therefore, the strength-decreasing factor of corrugated packaging box had to be investigated to determine the compression strength of the corrugated packaging box. This study was conducted to define the characteristics of moisture absorption as well as compression strength of corrugated fiberboard. (1) The moisture content of the corrugated fiberboard was rarely influenced by the kinds of raw materials and water repellent. However, the moisture adsorption of the corrugated fiberboard was shown to be clearly affected by air temperature changes. (2) The moisture content of the corrugated fiberboard was significantly affected by relative humidity. The moisture adsorption of corrugated fiberboard was also greatly influenced by composition of raw materials rather than water repellent. The results indicated that the improvement of raw materials was more effective than the increase of water repellent of corrugated fiberboard to reduce the moisture adsorption of the corrugated fiberboard. (3) The vertical compression strength was significantly decreased with increasing relative humidity. The reduction rate of vertical compression strength was not charged with the increase of relative humidity, which was regardless of kinds of corrugated fiberboard. (4) For improving the strength of the corrugated packaging box, new technique should be found to develop better quality of raw materials. Moreover, the physical construction of corrugated packaging box should be clearly understood because the corrugated packaging box for the agricultural products was usually used for the circumstances of high humidity and low air temperature