• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1805-1810
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• 2009

The adsorptions of trimethygallium (TMG) and arsine (As$H_3$) on H/Si(100)-2x1 surface were theoretically investigated. In the case of TMG adsorption, methane loss reaction, surface methylation, hydrogen loss reaction and ring closing reaction channels were found. The mechanism of As$H_3$ adsorption on the surface was also identified. Among these, the methane loss reaction depositing –Ga(C$H_3)_2$ was found to be the major channel due to its low barrier height and the large exothermicity. The surface methylation reaction is the second most favorable channel. In contrast, arsine turned out to be less reactive on the surface, implying that Arsine surface reaction would be the rate limiting step in the overall ALD process.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.283-288
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• 2019

Catalytic removal of sulfur compounds from heavy naphtha (HN) was investigated using a combination of an oxidation process using hydrogen peroxide and an adsorption process using granulated activated carbon (GAC) and white eggshell (WES). This study investigated the impact of changing several operating parameters on the desulfurization efficiency. Specifically, the volume ratio of $H_2O_2$ to HN (0.01~0.05), agitation speed ($U_{speed}$) of the water bath shaker ($100-500{\pm}1rpm$), pH of sulfur solution (1~5), amount of adsorbent (0.1~2.5 g), desulfurization temperature ($25{\sim}85{\pm}1^{\circ}C$) and contact time (10~180 minutes) were examined. The results indicate that the desulfurization efficiency resulting from catalytic and adsorption processes of GAC is better than that of WES for oxidation and removing sulfur compounds from HN due to its high surface area. The desulfurization efficiency depends strongly on all investigated operating parameters. The maximum removal efficiency of GAC and WES achieved by this study was 86 and 65, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.1
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• pp.63-68
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• 1982

This study was aimed ultimately to develop an adsorption process treating heavy metal industrial wastewater by utilizing domestically abundant natural zeolite and the study was conducted in a series of investigations. Presented if1 this paper are the results of the preliminary batch mode test. Factors affecting an adsorption process of heavy metals of aqueous waste stream by zeolite are numerous. Factors such as hydrogen ion concentration and temperature are taken into consideration in the investigation to evaluate adsorptive capacity. The mechanisms of adsorption may better be described by an evaluation of adsorption isotherm andi of adsorption kinetics. It is observed from the preliminary investigation that an optimum adsorption occurs at higher pH's than 4. It is further demonstrated that $Cd^{+2}$ adsorption by zeolite follows the BET model better than the Freundlich and the Langmuir model and that the reaction time of at least 10 minutes is required. It is interesting to note that higher adsorptive capacity was found at higher temperature, suggesting that the adsorption is not only due to simple physisorption but also due to chemisorption.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.2
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• pp.107-112
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• 2013

The ZnO is able to produce hydrogen from water however it can only absorb ultraviolet region due to its 3.37eV of wide band gap. Therefore efficiency of solar hydrogen production is low. In this work we report investigation results of improved visible light photo-catalytic properties of CdSe quantum dots(QDs) sensitized ZnO nanorod heterostructures. Hydrothermally vertically grown ZnO nanorod arrays on FTO glass were sensitized with CdSe by using SILAR(successive ionic layer adsorption and reaction) method. Morphology of grown ZnO and CdSe sensitized ZnO nanorods had been investigated by FE-SEM that shows length of $2.0{\mu}m$, diameter of 120~150nm nanorod respectively. Photocatalytic measurements revealed that heterostructured samples show improved photocurrent density under the visible light illumination. Improved visible light performance of the heterostructures is resulting from narrow band gap of the CdSe and its favorable conduction band positions relative to potentials of ZnO band and water redox reaction.

• Macromolecular Research
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• v.13 no.6
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• pp.521-528
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• 2005

Electrospun polyacrylonitrile (PAN) nanofibers were carbonized with or without iron (III) acetylacetonate to induce catalytic graphitization within the range of 900-1,500$^{circ}C$, resulting in ultrafine carbon fibers with a diameter of about 90-300 nm. Their structural properties and morphologies were investigated. The carbon nanofibers (CNF) prepared without a catalyst showed amorphous structures and very low surface areas of 22-31 $m^{2}$/g. The carbonization in the presence of the catalyst produced graphite nanofibers (GNF). The hydrogen storage capacities of these CNF and GNF materials were evaluated through the gravimetric method using magnetic suspension balance (MSB) at room temperature and 100 bar. The CNFs showed hydrogen storage capacities which increased in the range of 0.16-0.50 wt$\%$ with increasing carbonization temperature. The hydrogen storage capacities of the GNFs with low surface areas of 60-253 $m^{2}$/g were 0.14-1.01 wt$\%$. Micropore and mesopore, as calculated using the nitrogen gas adsorption-desorption isotherms, were not the effective pore for hydrogen storage.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.331-343
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• 2005

Development of hydrogen station system is an important technology to commercialize fuel cells and fuel cell powered vehicles. Generally, hydrogen station consists of hydrogen production process including desulfurizer, reformer, water gas shift (WGS) reactor and pressure swing adsorption (PSA) apparatus, and post-treatment process including compressor, storage and distributer. In this review, we investigate the R&D trends and prospects of hydrogen station in domestic and foreign countries for opening the hydrogen economy society. Indeed, the reforming of fossil fuels for hydrogen production will be essential technology until the ultimate process that may be water hydrolysis using renewable energy source such as solar energy, wind force etc, will be commercialized in the future. Hence, we also review the research trends on unit technologies such as the desulfurization, reforming reaction of fossil fuels, water gas shift reaction and hydrogen separation for hydrogen station applications.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.184-187
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• 2007

Hydrogen could be produced from any substance containing hydrogen atoms, such as water, hydrocarbon (HC) fuels, acids or bases. Hydrocarbon fuels couold be converted to hydrogen-rich gas through reforming process for hydrogen production. Even though fuel cell have high efficiency with pure hydrogen from gas tank, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. Most impurities are removed using pressure swing adsorption (PSA) process to get high purity hydrogen. However, high purity hydrogen production requires high operation cost of reforming process. The effect of carbon dioxide on fuel cell performance was investigated in this experiment. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run (10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography (GC).

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.21-34
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• 2021

Chitosan nanoparticles (CNPs) and Lactococcus lactis (L. lac.) were used as adsorbents to evaluate the adsorption performance of endocrine hormones, which are phthalates, in the healthy food packages. CNPs were produced through the cross bond with tripolyphosphate (TPP), and L. lac.-CNPs were prepared through the introduction of L. lac. during the preparation. The various functional groups of all adsorbents were identified using Fourier transform infrared spectroscopy (FTIR). Adsorption isotherm and adsorption kinetic confirmed the adsorption behavior and mechanism of CNPs, L. lac. and L. lac.-CNPs. The adsorption behavior of DBP and DEP for all particles was more suitable for the Freundlich adsorption isotherm model than for the Langmuir adsorption isotherm model, which means that the surface of the particles is heterogeneous. The adsorption mechanism was more suitable for the Pseudo-2nd-order model than for the Pseudo-1st-order model. This means that due to the presence of various functional groups on the particle surface, the adsorption of DBP and DEP is dominated by chemical adsorption such as electrostatic attraction and hydrogen bonding rather than physical adsorption. Finally, it was confirmed that the preparation of CNPs and L. lac.-CNPs can be performed easily and quickly, and it could be used as a cheaper adsorbent that can effectively remove phthalates.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.943-962
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• 2014

Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of $CO_2$ as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of $CO_2$ adsorption at given conditions and those points have been extensively described with literature data. A great body of data of $CO_2$ adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better $CO_2$ adsorbent for PSA processes.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.1
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• pp.72-79
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• 2010

This paper is studying the selective separation of methane and carbon dioxide which are the main ingredients of biogas. Adsorption performance of molecular sieve 13x for carbon dioxide seems to be reasonable. In this experiments carbon dioxide contains about 3~5 ppm of methane and it is impossible to obtain high purity carbon dioxide. Applying the low temperature technique, it is possible to separate methane and carbon dioxide from bio gas. PRO II simulation shows results a small change of liquefaction temperatures and no difference with the used thermodynamic models. Applying low temperature technique, It is possible to separate carbon dioxide and methane from biogas.