Korean Journal of Chemical Engineering (v.24, #5)
A lab-scale study on the humidity conditioning of flue gas for improving fabric filter performance by Ok Hyun Park; Gab Jun Yoo; Bong Jo Seung (717-722).
A centrifugal separator was constructed to examine the effect of flue gas humidity on the adhesional force between fabric and collected dust. A lab-scale fabric filter sampling system (FFSS) was also manufactured by using a piece of flat fabric as a sample of bag material. In addition, an automatic control system for gas humidity was devised and installed in the FFSS, and, then, the following effects were studied: (i) the influence of gas humidity on the adhesional force between fabric and dust particles; (ii) the influence of gas humidity on the performance of fabric filter in terms of pressure drop, ΔP, dust removal efficiency, η, and specific cake resistance, K′2; (iii) the variations in the composite-performance indices with gas humidity; and (iv) the influence of gas humidity on cleaning of dust-cake in terms of effective residual pressure drop. The main objectives were to determine the minimum and maximum values for the gas humidity range and to find the appropriate conditions for dust cleaning in terms of the critical value of effective residual pressure drop.
Keywords: Adhesional Force; Humidity Conditioning; Fabric Filter Performance; Effective Residual Pressure Drop; Specific Cake Resistance
Characterization of aquatic groundwater colloids by a laser-induced breakdown detection and ICP-MS combined with an asymmetric flow field-flow fractionation by Min-Hoon Baik; Jong-II Yun; Muriel Bouby; Pil-Soo Hahn; Jae-II Kim (723-729).
This study investigated the characteristics of natural groundwater colloids by a laser-induced breakdown detection (LIBD) and inductively-coupled plasma mass spectrometry (ICP-MS) in a combination with an asymmetrical flow field-flow fractionation (AsymFFFF). The groundwater was sampled from a borehole in the Yuseong area of Daejeon, Korea at different geological depths from 30 to 460 m and its geochemical parameters were measured. The combination of AsymFFFF and LIBD revealed a heterogeneous size fraction with a relatively broad size distribution of the groundwater colloids. One of the size fractions of the groundwater colloids was about 20 nm up to smaller than 100 nm, and the other fractions were larger than 100 nm. The elemental composition of the groundwater colloids was also analyzed by the AsymFFFF coupled with an ICP-MS. Results from the ICP-MS coupled with the AsymFFFF provided us with information about the size-specific elemental composition. The smaller sized fractions mainly consisted of calcite colloids with strontium, whereas the larger fractions were comprised of colloids such as aluminosilicates and iron oxides. The observations of all the groundwater samples indicate a similar pattern for the colloid fractions in size and in element composition except in the concentration.
Keywords: Groundwater Colloids; Laser-induced Breakdown Detection (LIBD); Asymmetric Flow Field-Flow Fractionation (AysmFFFF); Inductively-Coupled Plasma Mass Spectrometry (ICP-MS)
Simultaneous removal of chromium and organic pollutants in tannery wastewater by electroprecipitation technique by Sangkorn Kongjao; Somsak Damronglerd; Mali Hunsom (730-735).
The simultaneous removal of chromium and other organic pollutants from tannery wastewater was investigated in a batch electrochemical membrane reactor. This reactor, having a total capacity of 1 liter, was separated into two compartments (anodic and cathodic compartments) by using an anionic membrane. A stainless steel sheet with the square holes having total surface area of 0.0215 m2 and a Ti/RuO2 grid was used as the cathode and anode, respectively. The results indicated that the optimum condition for removal of chromium from tannery wastewater was found at the current density of 60.5 A/m2 at initial pH of 4.5. At this condition, more than 98% of chromium was removed within 60 min. Some organic pollutants contained in wastewater such as oil and grease, color and the level of biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total kjeldahl nitrogen (TKN) were also markedly reduced.
Keywords: Tannery Wastewater; Electroprecipitation; Chromium; Organic Pollutants; Removal
Pyrolysis of peat: Product yield and characterization by Hale Sutcu (736-741).
Pyrolysis of peat obtained from Yeniçağa, Bolu, Turkey was conducted in a fixed-bed tube furnace under various conditions, and variations in the structure of the char, tar and gas products were examined. The chars produced were studied by proximate and ultimate analyses. The maximum tar yield of 20.41% was obtained at a heating rate of 20 °C/min, a temperature of 450 °C, a sweeping gas flow rate of 100 ml/min and a 0.5–2.0 mm size range. The chemical composition of the tar was examined by elemental analysis, FTIR spectroscopy, 1H-NMR spectroscopy and column chromatography. The chemical composition of the tar with dense aliphatic structure was established to be CH1.22O0.25N0.02. The composition of the gases obtained at a heating rate of 20 °C/min for the 0.5–2.0 mm size range was examined by gas chromatography.
Keywords: Peat; Pyrolysis; Pyrolysis Temperature; Heating Rate; Sweeping Gas; Particle Size; Tar; Char; Gas
Photobiocatalytic hydrogen production in a photoelectrochemical cell by Jaekyung Yoon; Hyunku Joo (742-748).
In this study the photobiocatalytic hydrogen production system was photoelectrochemically examined. Preliminary experiments with a mixed slurry system revealed the following five facts: direct, inter-phase, electron transfer from photocatalyst to enzyme in the absence of electron relay was a rate-determining step; the enzyme was deactivated by irradiated light (half after 10 days); physical properties (crystallinity, specific surface area, pore volume and radius) of the photocatalysts, obtained by two preparation methods (sol-gel and hydrothermal), were seldom correlated with the production rate; chemical properties were postulated to have been affected; and each material needed different reaction conditions such as pH and temperature. For the later salt-bridged system, the I–V relation for each prepared photocatalyst was measured (V fb in the range of ca. −0.9∼−1.0 and V∞ close to −1.1 V vs. Ag/AgCl in saturated KCl). The change in the amount of evolved hydrogen was also independently checked according to external bias (critical bias around 1.0 V). Then both reaction components were connected through a salt bridge to initiate light-induced hydrogen production for the hybrid system. The H2 production exhibited an exponential trend and the Tris-HCl buffer showed the highest rate. A feasible reaction pathway was proposed.
Keywords: Photocatalyst; Photobiocatalytic; Hydrogenase; Hydrogen; Factorial Design
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process by Vasily V. Kokovkin; Sang Joon Chung; Subramanian Balaji; Manickam Matheswaran; Il-Shik Moon (749-756).
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant. The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III) concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction. The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction in the MEO process.
Keywords: Mediated Electrochemical Oxidation; Electrochemical Cell; Cerium; Nitric Acid; Oxygen Evolution Current; Organic Destruction
Manganese removal using an aerated granular filter by Bong-Yeon Cho (757-762).
Experiments on manganese removal using an aerated granular filter with mean particle size of 3.68 mm and 5.21 mm anthracite were conducted at a filtration rate of 100 m d−1. Air, with a rate of 0 to 366 m d−1, was supplied through nozzles positioned 100 mm above the filter column bottom. From the experiments that were conducted, it was found that manganese removal is completed at a pH of 9.6 or above. In addition, the oxidation and removal rate of dissolved manganese were expressed as a first-order reaction. The smaller the filter media particles were, the higher the manganese removal efficiency was. The aeration rate of dissolved oxygen in raw water is sufficient for the manganese removal process. The manganese removal rate increased with time due to the catalytic effect of manganese dioxide (MnO2) attached to the media. The x-ray diffraction analysis showed that the solids attached to the filter media were not crystalline but amorphous manganese.
Keywords: Aerated Filter; Manganese Removal; Aeration; Oxidation; X-Ray Diffraction; Amorphous
A new approach for estimating VOC emissions from anthropogenic non-point sources in urban communities by Mi-Sug Kim; Jong Ho Kim; Hyeon-Soo Park; Yle Shik Sun; Hong-Seok Kim; Kyunghee Choi; Jongheop Yi (763-773).
In an attempt to estimate VOC emission from anthropogenic, non-point sources in an urban area, a new approach (SKYEM) was introduced as a part of the integrated environment management (IEM) project. SKYEM was developed for consulting user convenience on a basis of emission inventory methodologies developed in the USA, Europe, Australia, and Korea. The inventory was obtained from mobile and area sources resolved to census tract levels (Dong or village levels). SKYEM was used to provide an annual emission inventory for major volatile organic compounds, BTXS (benzene, toluene, xylene, and styrene), PCE, phenol, and MEK, from 13 sources in multimedia (air, water, and soil) for 151 villages in northeastern Seoul. Toluene (73%) and Xlyene (16%) were largely emitted from important source categories, consumer solvents and mobiles, accounting for 60% and 26% of all estimated VOCs during the year 2002, respectively. BTXS were also measured at 10 sites located in the target area. Toluene presented the highest concentration (77%) with Xylene ranked second (15%). The similarity between concentration and emission may be explained by a model which describes scientific phenomena in or inter media. Therefore, a comparison of the prediction using the model with actual observations will be useful in examining uncertainties in, or the accuracy of the emission inventory from, non-point sources in an urban area.
Keywords: Emission Inventory; Non-point Source; Area Source; Mobile Source; BTXS; Urban
Effect of Pt addition on vanadium-incorporated TiO2 catalysts for photodecomposition of ammonia by Min-Kyu Jeon; Misook Kang (774-780).
This study investigated the effect of adding Pt components to V-TiO2 for highly concentrated ammonia photodecomposition. Pt components were introduced to the V-TiO2 photocatalysts by using two method types: the common sol-gel (Pt-V-TiO2) and impregnation (Pt/V-TiO2) methods. The observed X-ray diffraction (XRD) peaks were assigned to V2O5 at 19.5, 27.5 and 30.20° in V-TiO2, and to Pt metals at 39.80° (111) in Pt/V-TiO2. The Pt component of Pt-V-TiO2 was identified at Pt2+ from the Pt4f7/2 and Pt4f5/2 bands at 73.6 and 77.4 eV in XPS bands, respectively, but the band was shifted to a lower binding energy in Pt/V-TiO2. The H2 temperature-programmed reduction (TPR) curves showed that the temperature of reduction from Ti3+ to Ti0 was decreased by Pt addition and that the area was larger in Pt-V-TiO2 than in Pt/V-TiO2. The NH3 decomposition was slightly increased with vanadium addition compared to that of pure TiO2, and the decomposition was further enhanced with Pt addition. Particularly, the NH3 (1,000 ppm) decomposition reached 100% over Pt/V-TiO2 after 120 min, although about 10–30% of the ammonia was converted into undesirable NO2 and NO.
Keywords: Pt/V-TiO2 ; Pt-V-TiO2 ; NH3 Photodecomposition
Medium optimization of Rhodococcus erythropolis LSSE8-1 by Taguchi methodology for petroleum biodesulfurization by Yuguang Li; Jianmin Xing; Wangliang Li; Xiaochao Xiong; Xin Li; Huizhou Liu (781-786).
High production of Rhodoccus erythropolis LSSE8-1 and its application for the treatment of diesel oils was investigated. Culture conditions were optimized by Taguchi orthogonal array experimental design methodology. High cell density cultivation of biocatalyst with pH control and fed-batch feeding strategies was further validated in a fermentor with the optimal factors. Cell concentration of 23.9 g dry cells/L was obtained after 96 h cultivation. The resting cells and direct fermentation suspension were applied for deep desulfurization of hydrodesulfurized diesel oils. It was observed that the sulfur content of the diesel decreased from 248 to 51 μg/g by two consecutive biodesulfurizations. It implied that the biodesulfurization process can be simplified by directly mixing cell cultivation suspension with diesel oil. The biocatalyst developed with the Taguchi method has the potential to be applied to produce ultra-low-sulfur petroleum oils.
Keywords: Biodesulfurization; High Cell Density Cultivation; Rhodococcus erythropolis ; Taguchi Method
The formation of amyloid fibril-like hen egg-white lysozyme species induced by temperature and urea concentration-dependent denaturation by Steven S. -S. Wang; Ying-Tz Hung; Pu Wang; Josephine W. Wu (787-795).
Recent evidence has suggested that the formation of partially unfolded denatured intermediate serves as a crucial prerequisite for protein fibril formation/aggregation. Despite extensive exploration on amyloid fibril formation, the detailed molecular mechanism has remained largely unknown. Here, we examined the effects of urea on the denaturation of hen egg-white lysozymes. Our results demonstrated that, in the solutions (pH 7.4) with 8 M urea at all temperatures and with 4 M urea at 45 or 55 °C, the amyloid fibril-like species were first produced and then vanished while such species were not observed under other conditions. In addition, SDS-PAGE results further indicated that larger aggregated species with less ordered structures were formed at the later stage of the urea-induced unfolding process owing to an unidentified conformational switch. We believe that the results in this work will aid in deciphering the molecular mechanism(s) of protein denaturation.
Keywords: Lysozyme; Amyloid; Fibril; Aggregation; Urea; Partial Unfolding; Denaturation
The role of microenvironment in aggregation of the 293-human embryonic Kidney cells by Liang Zhao; Li Fan; Xu Zhang; Minglong Zhu; Wensong Tan (796-799).
The microenvironment severely affects aggregation and growth of human embryonic kidney 293-HEK cells. Key factors such as calcium, magnesium and shear stress were investigated in detail and cell aggregate size control was applied to facilitate cell retention improvement. It was found that the concentration of calcium ion affected the aggregation of 293-HEK cells drastically and exhibited direct proportion to the average diameter of 293-HEK cell aggregates. Similar effect was also discovered in magnesium but to a lower extend. Results also showed the growth of 293-HEK cells was influenced when the concentrations of calcium or magnesium ions were below 0.1 mmol/L, and that was more significant with magnesium. Furthermore, aggregation as well as growth was affected by hard intensive mechanical agitation. According to above results, the 293-HEK cell aggregates were successfully well controlled to proper size as anticipated and the average sedimentation speed of aggregated cells increased about 20 times to single cells. This is highly advantageous to cell retention improvement either in perfusion cultures or media exchange before adenovirus infection by proper control of the cell aggregate size, and thus a high cell concentration and adenovirus production potentially can be achieved.
Keywords: 293-HEK Cells; Aggregation; Microenvironment; Divalent Cation; Shear Stress
Determination of agitation and aeration conditions for scale-up of cellulolytic enzymes production by Trichoderma inhamatum KSJ1 by Jin-Ho Seo; Hongxian Li; Myong-Jun Kim; Seong-Jun Kim (800-805).
10 to 35 L jar fermentation scale-up cultures were performed to determine the optimum agitation and aeration rates in the cellulolytic enzymes production culture by Trichoderma inhamatum KSJ1. The optimum agitation rate in the 35 L jar fermenter was provisionally determined to be 150 rpm by using a geometrically resembled scale up method from the 10 L jar fermenter. The optimum aeration rate was determined to be 0.5 vvm by applying the mean values of superficial velocity and vvm. The DO (Dissolved Oxygen) concentration of the culture liquid was maintained below the critical DO concentration (2.336 mg/L) at 150 rpm in the 35 L jar fermenter. To increase the DO above the critical DO concentration, the agitation rate was increased from 150 to 200 rpm, with the aeration rate maintained at 0.5 vvm. As a result, the DO was maintained above critical DO concentration. The OUR (Oxygen Uptake Rate) and k L a values were 0.91 mg-DO/L·min and 11.1 hr−1, respectively. The amylase and FPase (filter paper activity) activities were 4.48 and 0.74 U/mL, respectively, in the 35 L jar fermenter, which was comparable to that in the 10 L fermenter (4.2 and 0.5 U/mL, respectively). Therefore, the scale-up conditions, 0.5 vvm and 200 rpm, were concluded to be the optimum aeration and agitation rates in the 35 L jar fermenter.
Keywords: Cellulolytic Enzyme Production; Scale-up; Agitation and Aeration Rate
Purification and characterization of a thermophilic chitinase produced by Aeromonas sp. DYU-Too7 by Te Sheng Lien; Shwu-Tzy Wu; Shin-Tsung Yu; Jui-Rze Too (806-811).
An extracellular chitinase, produced by Aeromonas sp. DYU-Too7, was purified in the following procedures: ammonium sulfate precipitation, ultrafiltration, chromatographic separation of DEAE-sepharose CL-6B and sephacrylS-100HR. The resulting chitinase has a molecular mass of 36 kDa, an optimal reaction pH of 5.0, and an optimal reaction temperature of 70°C. It retains almost 100% activity in the pH range of 5.0–8.0. This chitinase has a high thermal tolerance and retained 90% of its activity at 50°C and 75% at 60°C. Enzyme activity was inhibited by Ba2+, Hg2+, Mg2+ and Ag+ cations, but was not substantially inhibited by the K+ cation nor the chelating agent EDTA. The K m and V mα , using colloidal chitin as a substrate, are 6.3 g/L and 18.69 μmol/min/mg-protein, respectively. The 36 kDa chitinase of Aeromonas sp. DYU-Too7 is an exo-type enzyme, because chitobiose was the main hydrolysate in hydrolysis of colloidal chitin.
Keywords: Chitin; Chitinase; Aeromonas sp. DYU-Too7
Enhancement of secreted production of glucoamylase through fed-batch bioreactor culture of recombinant yeast harboring glucose-controllable SUC2 promoter by Hyung Joon Cha; Kyoung Ro Kim; Byeong Hee Hwang; Dae Hee Ahn; Young Je Yoo (812-815).
Glucoamylase that hydrolyses starch to glucose is one of the important industrial enzymes for ethanol production industry. Therefore, genetic production of recombinant glucoamylase has been widely studied. Previously, we reported secreted production of Saccharomyces diastaticus-originated glucoamylase in Saccharomyces cerevisiase expression system using its own signal sequence and the SUC2 promoter that is regulated by glucose level in culture medium. In the present work, we performed a comparative study between batch and fed-batch bioreactor cultures for secreted production of recombinant glucoamylase. Through maintaining low glucose levels in the culture broth, we obtained about 7-fold higher secreted production levels of glucoamlyase in fed-batch culture. Fed-batch culture strategy also enhanced (∼3.1-fold) secretion efficiency of recombinant glucoamylase in S. cerevisiae.
Keywords: Recombinant Yeast; Glucoamylase; SUC2 Promoter; Secreted Production; Fed-batch Culture
Functional biopolymers produced by biochemical technology considering applications in food engineering by Taous Khan; Joong Kon Park; Joong-Ho Kwon (816-826).
Polysaccharides are widely used in foods as thickening, gelling, stabilizing, emulsifying, and water-binding agents. The majority of the polysaccharides currently employed in the food industry are derived from plants and seaweeds. Recently, microbial polysaccharides have emerged as an important set of biothickeners for foods. These biopolymers have overcome to great extent the flaws associated with the plants and seaweeds polysaccharides. This relatively new class of biopolymers has unique rheological properties because of their potential of forming very viscous solutions at low concentrations and pseudoplastic nature. This review deals with the current applications of these microbial biopolymers in the food industry with a special focus on the commonly used important exopolysaccharides in this area.
Keywords: Microbial Exopolysaccharides; Foods Industry; Dextran; Xanthan; Bacterial Cellulose; Gellan; Curdlan; Pullulan
Depigmenting effect of Cinnamomum cassia Presl in B16F10 melanoma cells by Dung H. Nguyen; Duc T. M. Nguyen; Lyun-Hwa La; Sang-Hee Yang; Hyang-Bok Lee; Hae-Jong Kim; Jeong-Hyun Shin; Dong Man Kim; Eun-Ki Kim (827-830).
To find efficient depigmenting agents, we examined several Chinese herbs for melanogenesis inhibition and toxicity. Cinnamomum cassia Presl exhibited low cytotoxicity at even high concentration (200 μg/ml). The effects on melanogenesis of cultured B16 melanoma cells, mushroom tyrosinase activity, and free radical scavenging activity were further assessed. The methanol extracts of this plant showed the suppression of melanin synthesis. Melanin content was dose-dependently decreased by this herb extract as compared with control cells. It also showed good anti-oxidative activity (IC50=3.7 μg/ml) but no inhibition of mushroom tyrosinase activity. This result showed that Cinnamomum cassia Presl extract might be useful and safe as a new whitening agent in cosmetics.
Keywords: Melanogenesis; Depigmentation; Herb; Cinnamomum cassia Presl
Solubility of astaxanthin in supercritical carbon dioxide by Hyun-Seok Youn; Myong-Kyun Roh; Andreas Weber; Gordon T. Wilkinson; Byung-Soo Chun (831-834).
The solubility of astaxanthin in carbon dioxide was measured under supercritical conditions of a pressure range from 80 to 300 bar, and temperature range from 303 to 333 K, by using a dynamic flow-type. The solubility of astaxanthin increasing from 0.42×10−5 to 4.89×10−5 with higher temperature and pressure maintains certain density of supercritical carbon dioxide. The solubility data obtained were applied to the Chrastil model, based on the density of carbon dioxide. The data fitted well with the Chrastil model at most experimental conditions.
Keywords: Astaxanthin; Supercritical Carbon Dioxide; Solubility; Chrastil Model
A comparative study of different leaching processes for the extraction of Cu, Ni and Co from a complex matte by Kyung-Ho Park; Debasish Mohapatra; Chul-Woo Nam; Hong-In Kim (835-842).
The extraction behaviors of Cu, Ni and Co from a complex matte under different leaching conditions have been discussed. The synthetic Cu-Ni-Co-Fe-S matte was prepared by melting the pure metals. The matte contained 24.95% Cu, 35.05% Ni, 4.05% Co, 11.45% Fe, 24.5% S, similar composition as is expected to be obtained by reduction smelting of the Pacific Ocean nodules followed by sulphidisation of the alloy. The different phases identified are CuFeS2, CuS2, (FeNi)9S8, (FeNi)S2, Ni9S8, Ni3S2, (CoFeNi)9S8 and Co metal. The merits and demerits of each process of dissolution i.e., H2SO4/oxygen pressure leaching, atmospheric FeCl3 leaching, NH4OH/(NH4)2SO4 pressure leaching are discussed in detail. Out of the three, the H2SO4/oxygen pressure leaching process is found to be the most suitable with more than 99% metal extraction efficiency within 1 h of leaching time. From the X-ray diffraction analysis, the different undissolved phases corresponding to different leaching processes have been identified. The metal extraction efficiency decreased in case of atmospheric FeCl3 leaching and NH4OH/(NH4)2SO4 pressure leaching processes due to the formation of product layer such as elemental sulfur and goethite, respectively.
Keywords: Manganese Nodules; Matte; H2SO4 Pressure Leaching; NH4OH/(NH4)2SO4 Pressure Leaching; Atmospheric FeCl3 Leaching
Gauche conformation of acyclic guest molecules appearing in the large cages of structure-H clathrate hydrates by Kyuchul Shin; Youngjune Park; Jung Hoon Hong; Huen Lee (843-846).
In the present study, measurements and analyses were made of the High-Power Decoupling (HPDEC) solid-state 13C NMR spectra of structure-H (sH) methane hydrates with isopentane, one of the simplest and smallest acyclic large guest molecules, and methylcyclohexane (MCH), a commonly used cyclic guest molecule that is larger than isopentane. From the spectroscopic information, clear and definite evidence for the molecular conformation of acyclic guest molecules that are sufficiently small so as to be entrapped into the structure-H large cage (sH-L) was expected. The 13C NMR chemical shift change was additionally checked through the use of a hydrogen-hydrogen steric perturbation model. From the overall results, we concluded that one of the smallest acyclic guest molecules, isopentane, participating in the formation of a structure-H clathrate hydrate is encaged, confirming the gauche conformation in large cavities. The present results strongly suggest that the guest position and structure in hydrate cages are greatly influenced by both short-range interactions between guest molecules and cage frameworks and long-range interactions between small and large guests. Accordingly, cage dynamics must be carefully considered when a specific sH hydrate is designed and synthesized for the purpose of tuning material properties.
Keywords: Structure-H; Clathrate Hydrate; Large Guest Molecule Substance
Energetic surface heterogeneity of nanocrystalline TiO2 films for dye-sensitized solar cells by Jae-Wook Lee; Kyung-June Hwang; Wang-Geun Shim; Kyung-Hee Park; Hal-Bon Gu; Kyu-Hyuk Kwun (847-850).
Dye sensitized solar cells (DSSCs) have been receiving significant attention because they have many advantages compared to conventional organic solar cells. It has been known that the photovoltaic characteristics of DSSC are highly dependent on the adsorption properties of dyes on TiO2 films. To analyze the surface heterogeneity of TiO2 surfaces, single-phase anatase nanocrystallite titanium films were prepared by sol-gel method using the hydrolysis reaction of titanium tetraisopropoxide under acidic condition and characterized by XRD, FE-SEM and BET analysis. The adsorption energy distribution functions were calculated by the generalized nonlinear regularization method. It was found that the shape and the intensity of the adsorption energy distribution curve determined were highly related with the physical properties (i.e., geometrical heterogeneity) and chemical characteristics (i.e., energetic heterogeneity) of nanocrystalline TiO2 for DSSC.
Keywords: Adsorption Energy Distribution Functions; Dye-sensitized Solar Cell; TiO2 Film
Effect of air flowrate on particle velocity profile in a circulating fluidized bed by Sansanee Kumthanasup; Suchaya Nitivattananon (851-855).
The research was conducted in a cold flow circulating fluidized bed (CFB). The diameter and height of riser are 5 and 200 cm, respectively. The objective is to study effect of gas velocity on hydrodynamic of glass beads having mean diameter of 547 micron and density of 2,400 kg/m3. The measurement of particle velocity profile was achieved by using a high-speed camera and an image processing software. A probe of 0.5 cm in diameter was inserted into the riser at the height of 110 cm from gas distributor and was set at 3 positions along the radius of the riser; 0, 0.6, and 1.8 cm from center. Transport velocity (U tr ), core-annulus velocity (V CA ) and minimum pneumatic velocity (V mp ) were employed in determining solid flow pattern in the riser. It was observed that the flow regimes changed from fast fluidization to core-annulus and to homogeneous dilute bed when the gas velocities increased from 7, 8 and 9 m/s, respectively. The results from high-speed camera showed that glass beads velocity existed a maximum value at the center of the riser and gradually decreased toward the wall for all three gas velocities. It was also found that most of solid traveled upward in the core of the riser, however, solid traveled downward was identified at the wall layer.
Keywords: CFB; Glass Beads; Particle Velocity Profile; High-speed Camera
Fabrication of silver nanoparticles via self-regulated reduction by 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate by Sukjeong Choi; Ki-Sub Kim; Sun-Hwa Yeon; Jong-Ho Cha; Huen Lee; Chang-Jin Kim; Ick-Dong Yoo (856-859).
Silver nanoparticles exhibiting antimicrobial properties via self-regulated reduction were successfully prepared by using hydroxylated ionic liquids in an aqueous phase without additives. A new water-phase synthesis of silver nanoparticles using 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HEMIm][BF4]) and 1-(2′-hydroxyethyl)-2-methyl-3-dodecylimidazolium chloride ([C12HEMIm][Cl]) was described. 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate serves as both a reductant and a stabilizer in this fabrication. Furthermore, we presented the antimicrobial properties of the resulting silver nanoparticles through the minimal inhibitory concentrations (MIC) test.
Keywords: Ionic Liquid; Silver Nanoparticles; Antimicrobial Properties
Preparation of poly(L-lactic acid) submicron particles in aerosol solvent extraction system using supercritical carbon dioxide by Mi Yeong Kim; Ki-Pung Yoo; Jong Sung Lim (860-865).
The aerosol solvent extraction system process (ASES), which is one of the supercritical anti solvent processes (SAS), was used to produce poly(L-lactic acid) (PLLA) into the submicron particles. Dichloromethane (DCM, CH2Cl2) and carbon dioxide were selected as a solvent and as an antisolvent for PLLA, respectively. The objective of this study was to investigate the effect of the various process parameters such as temperature, pressure, and solution concentration on PLLA particles. With increasing temperature and pressure, particle size was increased. Also, higher PLLA concentration led to larger particle size and broader particle size distribution. A scanning electron microscope (SEM) was used to observe the morphology and size of PLLA particles recrystallized by ASES process. The mean particle size and its distribution of processed particles were measured by using a laser diffraction particle size analyzer (PSA).
Keywords: Poly(L-lactic acid); ASES Process; Supercritical Carbon Dioxide; SAS Processes; Nano-particles; Recrystallization
Pressure fluctuations and bubble size in viscous three-phase circulation fluidized bed bioreactors by Sung Mo Son; Ik Sang Shin; Suk Hwan Kang; Yong Kang; Sang Done Kim (866-871).
Characteristics of pressure fluctuations and bubble size were investigated in the riser of a three-phase circulation fluidized bed bioreactor with viscous liquid medium, whose diameter is 0.102 m (ID) and 3.5 m in height. Effects of gas (0.01–0.07 m/s) and liquid (0.17–0.23 m/s) velocities and liquid viscosity (0.96–38 mPa·s) on the bubble size in the riser were examined. The bubbling phenomena in the bioreactor with viscous liquid medium were interpreted effectively by measuring and analyzing the pressure fluctuations by adopting chaos theory. The bubble size increased with increasing gas velocity or liquid viscosity, but decreased with increasing liquid velocity. The bubbling phenomena became more complicated and bubble size distribution tended to broad, with increasing gas velocity or liquid viscosity. The bubble size was well correlated in terms of correlation dimension of pressure fluctuations as well as dimensionless groups within these experimental conditions.
Keywords: Pressure Fluctuations; Viscous Bioreactor; Bubble Size; Three-phase Circulation; Chaos Analysis
Synthesis of aluminum ethoxide from used aluminum cans by Seung-Joon Yoo; Ho-Sung Yoon; Hee Dong Jang; Seung-Tae Hong; Hyung-Sang Park; Sang-Ug Park; Dong-Heui Kwak; Se-Il Lee (872-876).
Aluminum ethoxide (AE) was synthesized to a high purity grade through dissolution reaction and vacuum distillation from used Al cans (UACs) under the condition of 3 mol C2H5OH/mol Al of stoichiometric ratio. 10−3 mol Hgl2/mol Al as a catalyst and 0.5 mol xylene/mol Al as a solvent for the control of reaction temperature were added. The UACs were cut into small pieces and heat-treated at the condition of 600 °C to remove impurities from UACs. Using the pretreated UACs, the high purity AE was synthesized and analyzed quantitatively by a complexometric method. The results of our experiment revealed that the reaction gives a 99.1% purity and 75% yield corresponding to the total amount of Al existing in the pretreated UACs.
Keywords: Used Aluminum Cans (UACs); Aluminum Ethoxide; Dissolution Reaction; Vacuum Distillation; High Purity
Comparison of YAG: Eu phosphors synthesized by supercritical water in batch and continuous reactors by Min-Jae Yoon; Yoan-Sang Bae; Sang-Ha Son; Jae-Wook Lee; Chang-Ha Lee (877-880).
Luminescent yttrium aluminum garnet (YAG, Y3Al5O12) nanoparticles doped with Eu (10 at%) were synthesized in batch-type and continuous-type supercritical water (SCW) reactors. In the case of the continuous-type SCW method, the particles of YAG: Eu phosphors were much smaller and demonstrated a uniform spherical-like shape. Inversely, in the case of the batch-type SCW method, a needle-like or elliptical-like shape was formed because a finite amount of time was required to reach SCW conditions from ambient conditions. However, the emission intensity of YAG: Eu phosphors synthesized by using the batch-type SCW method was stronger. Therefore, it is concluded that the continuous-type SCW method is superior to the batch-type SCW method from the viewpoint of the particle size and shape, but the luminescence property of phosphors in the continuous-type SCW method needs to be improved. In addition, a calcination process slightly improved the luminescence intensities of YAG: Eu phosphors generated by using either the batch-type or continuous-type SCW methods.
Keywords: Supercritical Water; Y3Al5O2 (YAG); Luminescent Properties; Batch Reactor; Continuous Reactor; Nanoparticle Phosphors
Effect of acid concentration and current density on DC etching of aluminum electrolytic capacitor foil by Chiu Yi Hung; Ou Bin Lung; Lee Yuoh Lien (881-887).
This work studies the effects of acid concentration and current density on etching morphology, microstructure and static capacity of the aluminum foils used in high-voltage electrolytic capacitors. The behavior associated with electrochemical etching was investigated with a potentiostat. The aluminum etching type of DC etching is greatly influenced by the etching potential. The static capacity increased to 0.65 uF/cm2 with 540 V forming voltage by optimization of the etching parameters used in this work.
Keywords: Capacitors; Aluminum Etching; Potential; Current Density
Structure and electrochemical characterization of LiNi0.3Co0.3Mn0.3Fe0.1O2 cathode for lithium secondary battery by Jong-Tae Son; Elton Cairns (888-891).
A lithium insertion material having the composition LiNi0.3Co0.3Mn0.3Fe0.1O2 was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO2 structure type (R3m; a=2.8689(5) Å and 14.296(5) Å in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi0.3Co0.3Mn0.3Fe0.1O2 when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi0.3Co0.3Mn0.3Fe0.1O2 in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.
Keywords: Cathode Material; LiNi0.3Co0.3Mn0.3Fe0.1O2 ; Sol-gel; Lithium Ion Battery
Residence time distribution and dispersion of gas phase in a wet gas scrubbing system by Uk Yeong Kim; Sung Mo Son; Suk Hwan Kang; Yong Kang; Sang Done Kim (892-896).
Residence time distribution (RTD) of exhaust gas in a wet scrubbing system was investigated for application to the removal of SO x , NO x or dust included in exhaust gas. The mixing of gas phase in the wet scrubbing system was also examined by considering the axial dispersion coefficient of gas phase. Effects of gas amount (velocity), liquid amount (velocity) and solid floating materials on the residence time distribution (RTD) and axial dispersion coefficient of exhaust gas were discussed. The addition of solid floating materials could change the RTD and thus dispersion of exhaust gas in the scrubbing system. The mean residence time and axial dispersion coefficient of exhaust gas were well correlated in terms of operating variables.
Keywords: Gas RTD; Wet Scrubbing System; Gas Dispersion Coefficient; Floating Materials
Oxygen permeability and structural stability of La0.6Sr0.4Co0.2Fe0.8O3−δ membrane by Jung Hoon Park; Sang Do Park (897-905).
La0.6Sr0.4Co0.2Fe0.8O3−δ oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature, but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen flux of La0.6Sr0.4Co0.2Fe0.8O3−δ membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane exposed to flowing air (P h =0.21 atm) and helium (P1=0.037 atm) is ca. 0.33 ml/cm2·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La2O3 and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both surfaces of membrane irrespective of spreading of glass sealing material.
Keywords: Ion Transport Membrane; Sealing; Perovskite Oxides; Oxygen Separation; Membrane Stability
NO x emission from incineration of organic liquid waste in a circulating fluidized bed by Hui-Chao Chen; Chang-Sui Zhao; Yong-wang Li; Duan-Feng Lu (906-910).
An incineration test of a toxic chemical organic waste liquid was conducted on a circulating fluidized bed (CFB) incinerator. The flue gas was measured online with the advanced SAE-19 flue gas analyzer. The effects of several factors, in terms of flow rate of waste liquid, ratio of waste liquid injected into dense bed of the CFB, excess air coefficient, the secondary air fraction and bed temperature on NO x emissions, were verified. The experimental results show that NO emissions in flue gas increase with increase in the flow rate of the waste liquid injected into the bed or the excess air coefficient or the bed temperature and those decrease with increase in the ratio of waste liquid injected into the dense bed of the CFB or the secondary air fraction. During the test runs, NO x concentration in flue gas met the national regulation on NO x emissions due to suppressive effect of low temperature and staged combustion in CFB on NO x formation.
Keywords: Red Waste Liquid; Incineration; Circulating Fluidized Bed (CFB); Emission
Prediction of coal slag foaming under gasification conditions by thermodynamic equilibrium calculations by Sukgyu Lim; Myongsook Oh (911-916).
In slagging gasifiers, slag foaming can cause serious operational problems, so there is a need for investigation into the conditions causing slag foaming. Viscosity experiments were carried out examining viscosity, extent of swelling and Fe formation. Although extensive swelling was not observed, FeO reduction was observed under an N2/CO gas atmosphere, but not under CO2/CO. In order to predict FeO reduction conditions in the gasifier, a model for an adiabatic equilibrium gasifier was developed. The gas composition, the amount of gas to slag, and Po2 were calculated for a slurry-feed gasifier, and the results of the calculation were used to predict the reduction of FeO in slag by using FactSage. Under typical gasification conditions for Denisovsky coal, the predicted P o2 in the gasifier was not low enough to cause FeO reduction. The FactSage simulation for the viscometer conditions predicted no FeO reduction under a CO/CO2 atmosphere, but did predict Fe formation under CO/N2 conditions. At a 20% CO concentration, FeO reduction starts at temperatures above 1,600°C. Since the slag has a low viscosity at 1,600°C, the oxygen bubble may have escaped as it formed. Therefore, slag foaming, caused by FeO reduction in the slag, can only occur when the right conditions of viscosity and oxygen partial pressure are met.
Keywords: Gasification; Slag; FeO Reduction; Foaming
Chemical fixation of carbon dioxide to dimethyl carbonate from propylene carbonate and methanol using ionic liquid catalysts by Hye-Young Ju; Mamparambath Dharman Manju; Kyung-Hoon Kim; Sang-Wook Park; Dae-Won Park (917-919).
The synthesis of dimethyl carbonate (DMC) through the transesterification of propylene carbonate (PC) with methanol was investigated by using imidazolium salt ionic liquid catalysts. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C2, C4, C6, C8) and anions (Cl−, Br−, BF 4 − , PF 6 − ) were used for catalysts. The reaction was carried out in an autoclave at 140–180°C under carbon dioxide pressure of 1.48–5.61 MPa. The imidazolium salts of shorter alkyl group, and more nucleophilic counter anion exhibited higher catalytic activity. The conversion of PC increased as CO2 pressure and reaction temperature increased. Kinetic studies were also performed to better understand the reaction mechanism.
Keywords: Dimethyl Carbonate; Transesterification; Propylene Carbonate; Methanol; Ionic Liquid