Korean Journal of Chemical Engineering (v.26, #1)
Multiresponse optimization based on the desirability function for a pervaporation process for producing anhydrous ethanol by Huu Hieu Nguyen; Namjin Jang; Soo Hyoung Choi (1-6).
A pervaporation process for producing anhydrous ethanol from industrial ethyl alcohol (95% v/v) was performed with a commercial PVA/PAN membrane. A central composite rotatable experimental design together with response surface methodology was implemented for studying and modeling the influence of operating conditions in terms of the temperature and the flow rate of the feed on the pervaporation performance, namely, the permeate flux and the separation factor. To obtain a trade-off between the permeate flux and the separation factor, a method for simultaneous optimization of multiple responses based on an overall desirability function was used. The optimization resulted in a feed temperature of 66 °C and a feed flow rate of 42 L/h. These operating conditions are expected to respond with a permeate flux of 0.107 kg/m2 h and a separation factor of 40, which correspond to a satisfactory overall desirability.
Keywords: Multiresponse Optimization; Overall Desirability Function; Central Composite Rotatable Design; Response Surface Methodology; Pervaporation
Modeling and control of the melt index in HDPE process by A. Ram Seong; Eun Ho Lee; Kyung Nam Lee; Yeong Koo Yeo (7-13).
We investigate the model for an industrial isothermal HDPE slurry reactor. The model, consisting of several nonlinear equations, can be linearized to give sets of linear time invariant state space model. The effectiveness of the linearized model is verified by the numerical simulations. A simple model predictive control scheme is constructed based on the linear state space model. The value of the melt index is obtained from the values of the manipulated and controlled variables generated from the control scheme. The control performance can be evaluated from the comparison between the computed melt index values and measured melt index values. The control scheme shows good tracking performance in the numerical simulations. We believe that the model developed in the present study can be effectively used to predict process variables as well as to control the melt index.
Keywords: Model Predictive Control; HDPE; Modeling and Simulation; Melt Index; Grade Change
A recursive PLS-based soft sensor for prediction of the melt index during grade change operations in HDPE plant by Faisal Ahmed; Salman Nazir; Yeong Koo Yeo (14-20).
An empirical model has been developed for the successful prediction of the melt index (MI) during grade change operations in a high density polyethylene plant. To efficiently capture the nonlinearity and grade-changing characteristics of the polymerization process, the plant operation data is treated with the recursive partial least square (RPLS) scheme combined with model output bias updating. In this work two different schemes have been proposed. The first scheme makes use of an arbitrary threshold value which selects one of the two updating methods according to the process requirement so as to minimize the root mean square error (RMSE). In the second scheme, the number of RPLS updating runs is minimized to make the soft sensor time efficient, while reducing, maintaining or normally increasing the RMSE obtained from first scheme up to some extent. These schemes are compared with other techniques to exhibit their superiority.
Keywords: Online Updating Scheme; Recursive Partial Least Square; Model Bias Updating; High Density Polyethylene (HDPE); Melt Index (MI)
Onset of solutal convection in liquid phase epitaxy system by Min Chan Kim; Sang Goo Lee (21-25).
The onset of convective instability in the liquid phase epitaxy system is analyzed with linear stability theory. New stability equations are derived under the propagation theory, and the dimensionless critical time τ c to mark the onset of the buoyancy-driven convection is obtained numerically. It is here found that the critical Rayleigh number Ra c is 8000, below which the flow is unconditionally stable. For Ra>Ra c the dimensionless critical time τ c to mark the onset of a fastest growing instability is presented as a function of the Rayleigh number and the Schmidt number. Available numerical simulation results and theoretical predictions show that the manifest convection occurs starting from a certain time τ o (> τ c ). It seems that during τ c ≤τ≤τ o secondary motion is relatively very weak.
Keywords: Onset of Convection; LPE System; Propagation Theory; Critical Rayleigh Number
Transient responses of two-dimensional viscoelastic film casting processes to sinusoidal disturbances by Seung Won Choi; Dong Myeong Shin; Joo Sung Lee; Ju Min Kim; Hyun Wook Jung; Jae Chun Hyun (26-31).
The sensitivity of two-dimensional isothermal film casting processes to ongoing sinusoidal disturbances has been investigated by using the frequency response method with transient simulation techniques. Amplitude ratios of state variables such as cross-sectional area, film width and film thickness at the take-up position with respect to a sinusoidal disturbance show resonant peaks along the frequency domain. Effects of operating conditions, such as drawdown ratio and aspect ratio, on the process sensitivity have been examined. Increasing drawdown ratio and decreasing aspect ratio make the system more sensitive to disturbances. Also, the dichotomous behavior in the sensitivity analysis using viscoelastic Phan-Thien and Tanner fluids has been elucidated. This frequency response method can be a useful tool to optimally design process systems for better processability and product quality.
Keywords: Sensitivity; Film Casting; Frequency Response; Transient Simulation; Sinusoidal Disturbance
Preparation of CuO-CeO2-Al2O3 catalyst with mesopore structure for water gas shift reaction by Jun-Keun Kim; Younghun Kim; Joo-Won Park; Jong-Soo Bae; Do-Young Yoon; Jae-Goo Lee; Jae-Ho Kim; Choon Han (32-35).
The water gas shift (WGS) reaction has been investigated widely in fuel cell technologies due to the potential for high fuel efficiency and lower emissions during the production of pure hydrogen. Industrially, the WGS reaction occurs in one of the following two ways: (a) high-temperature in the range of 310–450°C with Fe-Cr catalyst, (b) low-temperature in the range of 210–250°C with Cu-ZnO-Al2O3. In this study, a mesoporous catalyst was prepared, with a large surface area and uniformity in both pore size and distribution, by using a one-pot synthesis method. The prepared CuO-CeO2-Al2O3 brought high CO conversion (82%), and was suitable for WGS reaction at low temperature (250 °C).
Keywords: Ceria; CO Oxidation; Hydrogen Production; Mesoporous Alumina; Water Gas Shift (WGS)
Thermal decomposition of trichloroethylene under a reducing atmosphere of hydrogen by Yang-Soo Won (36-41).
The thermal reaction of trichloroethylene (TCE: C2HCl3) has been conducted in an isothermal tubular flow reactor at 1 atm total pressure in order to investigate characteristics of chlorinated hydrocarbons decomposition and pyrolytic reaction pathways for formation of product under excess hydrogen reaction environment. The reactions were studied over the temperature range 650 to 900 °C with reaction times of 0.3–2.0 s. A constant feed molar ratio C2HCl3: H2 of 4: 96 was maintained through the whole experiments. Complete decay (99%) of the parent reagent, C2HCl3 was observed at temperature near 800 °C with 1 s reaction time. The maximum concentration (28%) of C2H2Cl2 as the primary intermediate product was found at temperature 700 °C where up to 68% decay of C2HCl3 occurred. The C2H3Cl as highest concentration (19%) of secondary products was detected at 750 °C. The one less chlorinated methane than parent increased with temperature rise subsequently. The number of qualitative and qualitative chlorinated products decreased with increasing temperature. HCl and dechlorinated hydrocarbons such as C2H4, C2H6, CH4 and C2H2 were the final products at above 800 °C. The almost 95% carbon material balance was given over a wide range of temperatures, and trace amounts of C6H6, C4H6 and C2HCl were observed above 800 °C. The decay of reactant, C2HCl3 and the hydrodechlorination of intermediate products, resulted from H atom cyclic chain reaction via abstraction and addition replacement reactions. The important pyrolytic reaction pathways to describe the important features of reagent decay, intermediate product distributions and carbon mass balances, based upon thermochemical and kinetic principles, were suggested. The main reaction pathways for formation of major products along with preliminary activation energies and rate constants were given.
Keywords: Thermal Decomposition; Pyrolysis; Trichloroethylene (TCE); Reaction Pathway
LB energy-saving high temperature shift catalyst and its adsorption thermodynamics by Lingchao Wei; Fu’An Wang; Yi Liu; Yongli Chai (42-47).
This study prepared an LB energy-saving high temperature shift catalyst by optimizing its prepare parameters with artificial neural network, and measured its catalytic activities at various steam-gas ratios. It shows that the LB catalyst performs well at a lower steam-gas ratio. The chromatographic retention parameters of CO, CO2, and H2O on LB catalyst were experimentally determined by means of inverse gas chromatography (IGC). Adsorption enthalpies, Gibbs adsorption free energies and adsorption entropies of different gases were estimated by their retention volumes in infinite dilution region. The interaction parameters (χ) between absorbate gases and LB catalyst were calculated according to Flory-Huggins theory, and were inversely linear with temperature. The thermodynamics mechanism of the adsorption process was discussed from the view of the microcosmic factors of molecular structure and thermodynamic properties.
Keywords: Energy-saving High Temperature Shift Catalyst; Catalytic Activity; Adsorption Thermodynamics; Inverse Gas Chromatography; Water Gas Shift
Kinetic study and hydrogen peroxide consumption of phenolic compounds oxidation by Fenton’s reagent by Ana de Luis; José Ignacio Lombraña; Fernando Varona; Amaia Menéndez (48-56).
Synthetic solutions of phenol, o-, m- and p-cresol were oxidised by using Fenton’s reagent. The application of substoichiometric dosage of H2O2 led to the formation of intermediate compounds, continuing later the oxidation to complete oxidation. An important objective was to analyze the effect of hydrogen peroxide dosage applied and the reaction pH together with the iron oxidation state on the degradation level. A kinetic model was derived from a reaction mechanism postulated which was used to analyze the results of the experiments. Another aim was to analyze the hydrogen peroxide consumption. Noteworthy results include an increase in oxidant consumption to intensify phenol removal. Furthermore, oxidant consumption was analyzed through the ratio H2O2 to phenol removed and the average specific rate of removal (ASRR). By analyzing these two parameters it has been possible to ascertain the most favorable strategy for an efficient application of H2O2.
Keywords: Fenton; Phenol; Cresols; Hydrogen Peroxide
Catalytic synthesis of thiophene from the reaction of n-butanol and carbon disulfide over K2CO3-promoted Cr2O3/γ-alumina catalyst by Qi Feng Li; Chen Guang Liu; Jae Chang Kim (57-63).
The synthesis of thiophene from the reaction of n-Butanol and carbon disulfide was performed in a fixed-bed reactor in the presence of promoted chromia on γ-alumina. A high selectivity to thiophene (87%) and a long lifetime of the catalyst (55 hour) was obtained at 450 °C with a 1: 6 n-Butanol to carbon disulfide molar ratio and LHSV 1 h−1 over γ-Al2O3 promoted by 7% K2CO3 with 15% Cr2O3 loaded. The catalytic behavior of these catalysts can be attributed to their dual-functional acidity and dehydrogenating and cyclized properties.
Keywords: n-Butanol; Carbon Disulfide; Thiophene; γ-Alumina Based Catalyst; K2CO3
Separation and characterization of bitumen from Athabasca oil sand by Songhun Yoon; Sharad Durgashanker Bhatt; Wonkyu Lee; Heung Yeoun Lee; Soon Yong Jeong; Jin-Ook Baeg; Chul Wee Lee (64-71).
Separation and chemical analysis was investigated using bitumen samples from Athabasca oil sand in Alberta. Fractionation according to solubility and polarity has been used to separate bitumen into its fractions. The solvent de-asphaltening was performed by n-pentane solvent (solubility fractionation), and the polarity fractionation using Fuller’s earth allows maltene to separate into SARA components (saturates, aromatics, resins and asphaltenes). The SARA components are analyzed comprehensively using elemental analysis (EA), Fourier-transformed infrared (FTIR), ultraviolet-visible spectroscopy (UV-vis), high performance chromatography (HPLC) and thermogravimetric analysis (TGA). EA (C, H, N, S), heavy metals (Ni, V) concentrations, FT-IR and UV-vis tests provided the explanation of chemical composition. From IR spectra, maltene and saturates/aromatics (sat/aro) contained more aliphatic compounds than resin or asphaltene. Also, IR spectrum of sat/aro was similar to crude oil and VGO (vacuum gas oil). Different UV signal data clearly indicates the contribution of aromatic constituents in the fractions. Using optimized analysis conditions of HPLC, we successfully separated the peaks for bitumen and its fractions. The characteristic peak pattern of SARA (saturates, aromatics, resins, asphaltenes) fractions was observed, and also the peak pattern of sat/aro was similar to that of crude oil and VGO. However, TGA results revealed that thermal behavior for sat/aro was similar to that of crude oil but different from that of VGO. Also, from the comparison between decomposition temperature of TGA and boiling point, their correspondence was found.
Keywords: Oil Sand; Separation; Bitumen; Heavy Oil; Spectroscopy
Computational fluid dynamic analyses of catalytic combustors for 100 kW-class molten carbonate fuel cell by Hai-Kyung Seo; Donghoon Shin; Jae Hwa Chung; Beomjoo Kim; Soo Man Park; Hee Chun Lim (72-78).
The asymmetric inner structure of a catalytic combustor causes wall cracking because of regional overheating. Thus, a symmetric shape is proposed in the present work and analyses of the computational fluid dynamics of the existing combustor and the proposed type have been performed. A simulation of the revised combustor without a swirl device revealed that the flow of gases is concentrated on the center of the combustor and only catalysts around the center are used. In the revised combustor with a swirl device, the overall temperatures were estimated to be uniform. However, near the swirl device, high temperature exceeding 1,700 K was measured. Therefore, a heatproof surface coating on the swirl device is necessary for protection of the material. At the initial start-up of the catalytic combustor, hydrogen and natural gas are used. When only natural gas is used, the simulation indicated that the gas does not burn in the revised combustor without a swirl device. However, in the combustor with the swirl device, methane of 34.8% volume burns in the simulation. On the other hand, when hydrogen and natural gas are burned together, methane of 91.7% volume burns in the simulation.
Keywords: Catalytic Combustor; Asymmetric Structure; CFD; Swirl Device; Anode Off Gases
Simultaneous biofiltration of H2S, NH3 and toluene using cork as a packing material by Byoung-Gi Park; Won Sik Shin; Jong-Shik Chung (79-85).
Simultaneous removal of ternary gases of NH3, H2S and toluene in a contaminated air stream was investigated over 185 days in a biofilter packed with cork as microbial support. Multi-microorganisms including Nitrosomonas and Nitrobactor for nitrogen removal, Thiobacillus thioparus (ATCC 23645) for H2S removal and Pseudomonas aeruginosa (ATCC 15692), Pseudomonas putida (ATCC 17484) and Pseudomonas putida (ATCC 23973) for toluene removal were used simultaneously. The empty bed residence time (EBRT) was 40–120 seconds and the inlet feed concentration was 50-180 ppmv for NH3, 30–160 ppmv for H2S and 40–130 ppmv for toluene, respectively. The observed removal efficiency was 45–100% for NH3, 96–100% for H2S, and 10–99% for toluene, respectively. Maximum elimination capacity was 5.5 g/m3/hr for NH3, >20.4 g/m3/hr for H2S and 4.5 g/m3/hr for toluene, respectively. During long-term operation, the removal efficiency of toluene gradually decreased, mainly due to depositions of elemental sulfur and ammonium sulfate on the cork surface. The results of microbial analysis showed that nearly the same population density was observed on the surfaces of cork chips collected at each sampling point. Kinetic model analyses showed that there were no particular evidences of interactions or inhibitions among the microorganisms.
Keywords: Ammonia; Biofilter; Cork; Hydrogen Sulfide; Odor; Carrier; Toluene
Simultaneous removal of particulates and NO by the catalytic bag filter containing MnOx catalysts by Min Kang; Eun Duck Park; Ji Man Kim; Jae Eui Yie (86-89).
A catalytic bag filter which can remove particulates and NOx simultaneously was prepared and tested in a laboratory and a pilot plant. Manganese oxides (MnOx), active for the selective NO reduction with NH3 at low temperatures, was utilized as the catalyst. This MnOx-coated bag filter showed 92.6% NOx conversion at 423 K with a space velocity of 400,000 h−1.
Keywords: Catalytic Bag Filter; Particulates Removal; NO Reduction; NH3-SCR
Control of corrosive water in advanced water treatment plant by manipulating calcium carbonate precipitation potential by Do-Hwan Kim; Jae-Hwan Cha; Soon-Heon Hong; Dong-Youn Kim; Chang-Won Kim (90-101).
The corrosion of metal pipes in water distribution networks is a complex electrochemical and physicochemical phenomenon between a metal surface and corrosive water. The level of corrosion in water distribution systems was controlled by manipulating the calcium carbonate precipitation potential (CCPP) concentration, and the corrosive water quality was controlled in two steps within the advanced water treatment plant (AWTP) constructed at the Institute of Water Quality Research (IWQR), Busan Metropolitan City, Korea. The 1 st control step was located before a coagulation process included on a rapid mixer, and the 2 nd control step was located after a biological activated carbon (BAC) process. The capacity of the AWTP in IWQR was 80 m3/day. The CCPP concentration was controlled from the calcium hardness, alkalinity, and pH by adding calcium hydroxide (Ca(OH)2), sodium carbonate (Na2CO3), and carbon dioxide (CO2) in the above two steps. A CCPP control system was installed and operated according to the developed algorithm to maintain a CCPP range of 0–4 mg/L. The CCPP range was reasonably controlled to induce the formation of a CaCO3 film on the surface of the simulated water distribution system (SWDS). From the result of the corrosive water control, the CCPP formed greater than 0.0 mg/L. The crystalloid structure of the scale produced by CCPP control in the inner surface of pipe was zinc carbonate hydroxide hydrate (Zn4CO3(OH)6·H2O).
Keywords: Corrosive Water; Corrosion Control; CCPP; BAC; Water Pipe
Studies on auramine dye adsorption on psidium guava leaves by Ravindra Wamanrao Gaikwad; Sunil Ashok Misal Kinldy (102-107).
Removal of auramine dye from aqueous waste solutions was investigated by using very cheap and biosorbent, withered guava tree leaves and activated carbon. Guava leaves are readily available in the western and northern parts of India throughout the year, and hence form a cost effective alternative for removal of dyes from waste waters. The optimum contact time was found to be 120 min. in a pH range of 8–9 for 92–94% removal of the dye from aqueous solutions containing 150 mg/L of auramine dye using 2 g of the adsorbent. The effect of pH, dye concentration, sorbent dosage, temperature and contact time on the dye removal efficiency has been studied. Experimental results were found to fit both Freundlich and Langmuir models. Since the dye contains a cationic species, the removal efficiency was highest in a pH range of 8–9. Continuous adsorption studies in a packed column showed 100% removal efficiency for a flow rate of 10 ml·min−1. When compared with the activated carbon, it was also found that adsorbent derived from guava leaves is more efficient in removal of dye.
Keywords: Auramine Dye Removal; Guava Leaves; Adsorption Isotherms; Adsorption Kinetics; Breakthrough Curve
Biological leaching of nickel and cobalt from lateritic nickel ore of Sukinda mines by Smaranika Mohapatra; Chandan Sengupta; Bansi Dhar Nayak; Lala Bihari Sukla; Barada Kanta Mishra (108-114).
In the present study lateritic nickel ore was used for bacterial leaching using a mixed consortium of mesophilic acidophiles. The microorganisms were adapted to 1 gram nickel/L prior to leaching. For the experiments, lateritic ore in different forms such as raw, roasted, roasted ore presoaked in dilute sulphuric acid and palletized pretreated roasted (400 °C and 600 °C) ore were taken. The leaching experiments were conducted in 9 K+ with 40 L capacity bioreactor using 10% (v/v) inoculum concentration at 10% (w/v) pulp density. The aeration was maintained at 2–3 L/min and the speed of agitator and temperature at 400–500 rpm and 35 °C. The maximum extraction of nickel and cobalt was observed with pretreated ore (600 °C) at 10% pulp density (77.23% and 73.22%) respectively within 31 days at pH 1.5 and least extraction in case of raw ore i.e., 9.47% nickel and 41.12% cobalt respectively.
Keywords: Lateritic Nickel Ore; Roasted Ore; Pretreated Ore; Nickel; Cobalt; Mesophilic; Acidophilic; 40 L; Bioreactor
Gene expression profiling in streptozotocin-induced diabetic rat liver in response to fungal polysaccharide treatment by Hye Jin Hwang; Sang Woo Kim; Yu Mi Baek; Sung Hak Lee; Hee Sun Hwang; Jong Won Yun (115-126).
We established the gene expression profiling in streptozotocin (STZ)-induced diabetic rat liver in response to hypoglycemic fungal polysaccharides (EPS), using oligonucleotide microarray analysis. Differentially regulated genes showing higher fold change than 2 were identified and categorized through hierarchical clustering analysis. Among the 835 genes analyzed, 244 were up-regulated, while 321 were down-regulated after diabetes induction. Interestingly, many gene expressions altered after STZ-treatment mimicked a normal rat liver by EPS therapy. Most of these genes included genes involving cell structure and motility, immunity and defense, lipid, fatty acid and steroid metabolism, protein metabolism and modification, and signal transduction. More importantly, we found a total of 36 genes that showed significant fold changes in their expression that have not previously been examined in the context of diabetes. To validate the microarray results, we further confirmed the gene expression patterns by RT-PCR using four genes of interest (carboxylesterase 2, stearoyl-coenzyme A desaturase 1, insulin-like growth factor 1, and insulin-like growth factor binding protein 2). Taken together, EPS acted as a potent regulator of gene expression for a wide variety of genes in diabetic rat liver.
Keywords: Diabetes Mellitus; Fungal Polysaccharides; Gene Profile; Microarray; Streptozotocin
Immobilization of lipase on surface modified magnetic nanoparticles using alkyl benzenesulfonate by Kanagasabai Muruganandam Ponvel; Dong-Geun Lee; Eun-Ji Woo; Ik-Sung Ahn; Chang-Ha Lee (127-130).
The surface of nano-sized magnetite (NSM) particles synthesized by coprecipitation method was modified by alkyl benzenesulfonate (ABS) as a coating material. ABS on the NSM was expected to form a spacer between the surface of the NSM particles and the enzyme adsorbed and to play a role of strong enzyme adsorption onto a hydrophobic surface. Transmission electron microscopy showed that the NSM particles had an average size of 10 nm. Magnetic measurement revealed that the nanoparticles were superparamagnetic and the saturation magnetization was about 68 emu/g. Porcine pancreas lipase (PPL) was immobilized onto the ABS-NSM, which was to catalyze hydrolysis of olive oil and showed enhanced durability in the reuse after being recovered by magnetic separations.
Keywords: Alkyl Benzenesulfonate; Lipase; Nano-sized Magnetite; Enzyme Immobilization
Enhanced oral absorption of salmon calcitonin-encapsulated PLGA nanoparticles by adding organic substances by Tae-Sung Jung; Byung-Soo Kwon; Hea-Eun Lee; Ah-Young Kim; Min-Jeong Lee; Cho-Rong Park; Ho-Kyung Kang; Young-Deug Kim; Sang-Kil Lee; Jae-Seon Kang; Guang-Jin Choi (131-135).
Two organic compounds with potential absorption enhancing effects, bile acids and transferrin, were examined by the gastro-intestinal (GI) absorption of therapeutic salmon calcitonin (sCT) as encapsulated by poly(lactide-co-glycolide) (PLGA) for the treatment of osteoporosis. The sCT-loaded PLGA nanocapsules were prepared by O/W emulsification approach. Either additive of a designated content was mixed with sCT dissolved in methanol. For bile acids, their content (0–7.5 mg to sCT 6 mg) was observed to have a substantial effect both on the emulsification process and the encapsulation efficiency. When 1.5 mg of bile acids was added, sCT-loaded PLGA nanocapsules of about 700 nm in diameter and with a fairly high encapsulation efficiency greater than 35% were produced. Accordingly, this formulation gave the most significant hypocalcemic effect in an in vivo experiment with SD rats. On the other hand, a too high bile acids loading resulted in a poor encapsulation efficiency of less than 7%. Two principal roles of bile acids were proposed: emulsifying agent and absorption enhancer. Transferrin, a human glycoprotein of 80 kDa molecular weight, turned out to have potential as absorption enhancer as well.
Keywords: Salmon Calcitonin; Poly(lactide-co-glycolide); PLGA, Absorption Enhancer; Bile Acid; Transferrin; Oral Delivery; Encapsulation
Properties of bacterial cellulose produced in a pilot-scale spherical type bubble column bioreactor by Chang Nam Choi; Hyo Jeong Song; Myong Jun Kim; Mi Hwa Chang; Seong Jun Kim (136-140).
The saccharogenic liquid obtained by the enzymatic saccharification of food wastes was used as a medium for production of bacterial cellulose (BC). The enzymatic saccharification of food wastes (SFW) was carried out by the cultivation supernatant of Trichoderma inhamatum KSJ1. 5.6 g/L of BC was produced in a new modified 50 L bubble column bioreactor by Acetobacter xylinum KJ1. The productivity was similar to that of a modified 10 L bubble column bioreactor (5.8 g/L). When pure oxygen was supplied into the scaled-up culture conditions, 6.8 g/L (12% enhancement) of BC was produced, indicating a very useful method for BC mass production. The oxygen uptake rate (OUR) and q O2 (specific oxygen uptake rate) were 0.214 mg-DO/L·min and 0.257 mg-DO/g-cell·min, respectively. The physical properties, such as morphology, molecular weight, crystallinity, and tensile strength of BCs produced in static culture (A), 10 L (B) and 50 L (C) modified bubble column cultures were investigated. All BCs showed fibrils with highly networking structure. The number average molecular weight of BCs in A, B and C was 2,314,000, 1,878,000, and 1,765,000, respectively. All of the BCs had a form of cellulose I representing pure cellulose. The relative degree of crystallinity showed the range of 79.6–86.0%. Tensile strengths of BC sheet in A, B and C were 1.75, 1.21, and 1.19 kg/mm2, respectively. In conclusion, BC production by the modified bubble column culture mode of 50 L brought more favorable results in terms of the physical properties and its ease of scale-up.
Keywords: Saccharification of Food Wastes (SFW); Bacterial Cellulose (BC); Pilot Scale Production; Modified Bubble Column Bioreactor; Physical Properties
Pilot-scale production of bacterial cellulose by a spherical type bubble column bioreactor using saccharified food wastes by Hyo-Jeong Song; Hongxian Li; Jin-Ho Seo; Myong-Jun Kim; Seong-Jun Kim (141-146).
Bacterial cellulose (BC) was produced by Acetobacter xylinum KJ1 in a modified airlift-type bubble column bioreactor, which had a low shear stress and high oxygen transfer rate (k L a). Saccharified food wastes (SFW) were used as the BC production medium due to its low cost. An aeration rate of 1.2 vvm (6 L/min) was tentatively determined as the optimal aeration condition in a 10 L spherical type bubble column bioreactor, by analysis of the oxygen transfer coefficient. When 0.4% agar was added, the BC production reached 5.8 g/L, compared with 5.0 g/L in the culture without the addition of agar. The BC productivity was improved by 10% in the addition of 0.4% agar into the SFW medium. Then, by conversion of a linear velocity of 0.93 cm/sec, from the relationship between the linear velocity and oxygen transfer rate, 1.0 vvm (30 L/min) was determined as an optimal aeration condition in a 50 L spherical type bubble column reactor. Using SFW medium, with the addition of 0.4% agar, and air supplied of 1.0 vvm, 5.6 g/L BC was produced in the 50 L spherical type bubble column bioreactor after 3 days of cultivation, which was similar to that produced in the 10 L bioreactor. In conclusion, the addition of agar, a viscous polysaccharide, into SFW medium is effective for the production of BC, and this scale-up method is very useful for the mass production in a 50 L spherical type bubble column bioreactor by decreasing the shear stress and increasing the k L a.
Keywords: Scale-up; Bacterial Cellulose; Saccharified Food Wastes; Spherical Type Bubble Column Bioreactor
Phase diagram prediction of recycling aqueous two-phase systems formed by a light-sensitive copolymer and dextran by Zhihua Shao; Fanqi Kong; Xuejun Cao (147-152).
Our Laboratory has synthesized a novel light-sensitive and recycling copolymer P NBC . The P NBC copolymer could form recycling aqueous two-phase systems with Dextran. Recycling aqueous two-phase systems have important application in bioseparation engineering. Phase diagram prediction of the novel aqueous two-phase systems also is an important aspect in engineering. This article applied the Cabezas model and effective excluded volume (EEV) model to the experimental data of light-sensitive recycling aqueous two-phase systems. It has been found that the EEV model could consist with experimental data very well. The maximum absolute error and average absolute error is 0.81% (wt%) and 0.23% (wt%), respectively.
Keywords: Aqueous Two-phase Systems; Light-sensitive Polymer; Liquid-liquid Equilibria; Thermodynamic Models
Preparation of colloidal silver nanoparticles by chemical reduction method by Ki Chang Song; Sung Min Lee; Tae Sun Park; Bum Suk Lee (153-155).
Colloidal silver nanoparticles were obtained by chemical reduction of silver nitrate in water with sodium borohydride (NaBH4) in the presence of sodium dodecyl sulfate (SDS) as a stabilizer. The obtained nanoparticles were characterized by their UV-vis absorption spectra and transmission electron micrograph (TEM) images. The UV-vis absorption spectra showed that NaBH4 served not only as a reducing agent but also as a stabilizer, which protects the aggregation of silver nanoparticles. The TEM images showed that the particles were dispersed better with increasing the NaBH4 concentration.
Keywords: Silver Nanoparticles; Chemical Reduction; SDS; UV-vis Absorption Spectra; TEM
Increased production of S-adenosyl-L-methionine using recombinant Saccharomyces cerevisiae sake K6 by Eun-Sil Choi; Bu-Soo Park; Sang-Woo Lee; Min-Kyu Oh (156-159).
S. cerevisiae sake K6 was the firstly isolated industrial strain to overproduce S-adenosyl-L-methionine (SAM). Although the strain has advantages over other strains, such as GRAS (generally recognized as safe) property, the S. cerevisiae K6 has not been further developed with DNA recombinant technology due to the lack of a proper genetic marker. In this study, UV mutagenesis was conducted with S. cerevisiae sake K6. With the method, a mutant of sake yeast with leucine auxotroph, K6-1, was isolated. The mutant showed comparable growth rate and SAM productivity with its wild type. Using the auxotroph as a genetic marker, a SAM synthase in S. cerevisiae, SAM2, was overexpressed in the mutant strain. This recombinant DNA technology successfully increased SAM productivity in sake yeast.
Keywords: S-Adenosyl-L-methionine; Saccharomyces cerevisiae Sake; Auxotrophic Mutant; Recombinant DNA
Improvement of sensitivity in an interferometry by controlling pore size on the anodic aluminum oxide chip pore-widening technique by Hee Chul An; Jin Young An; Byung-Woo Kim (160-164).
The pore size of an anodic aluminum oxide (AAO) chip, as well as uniform pore distribution, is one of the key parameters that should be adjusted, by choosing the appropriate etching conditions, in order to enhance the sensitivity of an interferometer. In this study, the pore size of AAO chips was optimized and characterized in order to lower the detection limit of prostate specific antigen (PSA) in an interferometric immunoassay system. After pore widening for 30–50 min, the AAO pore size was increased approximately 2-fold larger than that before pore widening. A large increase in effective optical density (ΔEOT) was obtained from the AAO chip fabricated by pore-widening technique, which thereby lowered the PSA detection limit. The present study results are not sufficiently validated to enable the immediate application to immunoassay for prostate cancer (PCa) screening, but they do demonstrate that controlling pore size can positively affect the sensitivity and lower the detection limit.
Keywords: Interferometry; Biosensor; Anodic Aluminum Oxide (AAO); Prostate Specific Antigen (PSA); Pore Widening
Microwave-assisted dissolution of UO2 with TBP-HNO3 complex by Yunfeng Zhao; Jing Chen (165-167).
The direct dissolution of UO2 in TBP-HNO3 complex by microwave heating in this study suggests the possibility of dissolving spent nuclear fuels. This new technique offers many benefits for reduction in aqueous and organic waste generation and improved efficiency of chemical processing. The dissolution rate of UO2 particles with TBP-HNO3 complex by microwave assisted heating is highly dependent on the temperature and the particle size.
Keywords: Uranium Dioxide; Dissolution; Microwave Heating; Tri-n-butylphosphate
Equation of state for the systems containing aqueous salt: Prediction of high pressure vapor-liquid equilibrium by Hadi Baseri; Mohammad Nader Lotfollahi; Ali Haghighi Asl (168-174).
An equation of state (EOS), which is based upon contributions to the Helmholtz energy, is presented for systems containing aqueous electrolyte solutions at high pressure. The Peng-Robinson equation of state is used to provide the Helmholtz energy of a reference system. The electrolyte terms consist three terms containing a modified Debye-Hückel term for long-range electrostatic interactions, the Born energy contribution for electrostatic works and a Margules term for short-range electrostatic interactions between ions and solvents. The binary and ternary interaction parameters of the equation of state are obtained by experimental osmotic coefficient data. Systems that were studied here are (water+ NaCl+SC-CO2), (water+NH4Cl+SC-CO2), (water+Na2SO4+SC-CO2) and (water+methanol+NaCl+SC-CO2). It is found that the proposed equation of state is able to accurately represent the experimental data over a wide range of pressure, temperature and salt concentration.
Keywords: Equation of State; Electrolyte Solution; Vapor-liquid Equilibrium
Kinetics of nucleation and growth of L-sorbose crystals in a continuous MSMPR crystallizer with draft tube: Size-independent growth model approach by Bogusława Wierzbowska; Krzysztof Piotrowski; Joanna Koralewska; Nina Hutnik; Andrzej Matynia (175-181).
The experimental data concerning kinetics of a continuous mass crystallization in L-sorbose - water system are presented and discussed. Influences of L-sorbose concentration in a feeding solution and mean residence time of suspension in a working volume of laboratory DT MSMPR crystallizer on the resulting crystal size distributions, thus on the nucleation and growth kinetics, were determined. The kinetic parameter values were evaluated on the basis of size-independent growth (SIG) kinetic model (McCabe’s ΔL law). It was observed that within the investigated range of crystallizer productivity (220–2,200 kg of L-sorbose crystals m−3 h−1), a crystal product of mean size Lm from 0.22 to 0.28 mm and CV from 68.8 to 44.0% was withdrawn. The values of linear growth rate show increasing trend (from 6.6·10−8 to 7.6·10−8 m s−1) with the productivity enlargement (assuming constant residence time τ=900 s). Occurrence of secondary nucleation phenomena within the circulated suspension, resulting from the crystals attrition and breakage was observed. The parameter values in a design equation, matching linear growth rate and suspension density with nucleation rate were determined.
Keywords: L-Sorbose; Continuous Mass Crystallization; Water Solution; Draft Tube (DT) Crystallizer; Size-independent Growth (SIG) Kinetic Model
Nonlinear isotherm of benzene and its derivatives by frontal analysis by Xiaolong Wan; Ju Weon Lee; Kyung Ho Row (182-188).
Adsorption behavior of a solute is one of the most important factors to consider when designing a batch and a continuous liquid chromatographic separation process. In liquid chromatography, this behavior is based on the adsorption equilibrium between the liquid mobile-phase and solid stationary-phase. However, most retention models have been developed under a linear adsorption isotherm: very few researchers have investigated the relationship between the adsorption parameters and the mobile phase composition, and some empirical models have been introduced. In this work, adsorption isotherms were obtained by a frontal analysis for three small molecular compounds (benzene, toluene, and chlorobenzene) on a commercial C18 bonded silica column. The absorption based on the Langmuir, Freundlich, and Langmuir-Freundlich models were investigated according to changes of the composition of methanol highly enriched eluent. The calculations and analysis of the coefficients obtained for the three models confirm that the adsorption data for solutes are best modeled with the Langmuir-Freundlich isotherm. In spite of the acceptable accuracy, Langmuir and Freundlich isotherm models couldn’t satisfactorily describe the mechanism and provide objective information on the physical nature of the absorption.
Keywords: Adsorption Isotherm Modeling; Frontal Analysis; Mobile Phase Composition
Vapor-liquid equilibria of water+monoethanolamine system by Sung Jin Park; Hun Yong Shin; Byoung-Moo Min; Ara Cho; Jeon-Seop Lee (189-192).
The accurate design of carbon dioxide separation processes by the absorption method requires knowledge of the vapor-liquid equilibrium of aqueous alkanolamine systems. MEA (monoethanolamine) is widely used for the separation of carbon dioxide by the chemical absorption process. The equilibrium apparatus was tested by comparing the measured VLE data for the methanol+ethanol system with the literature data. The isobaric vapor liquid equilibrium data were measured for the water+MEA binary system by using a modified Stage-Muller equilibrium still with circulation in both phases. The vapor liquid equilibrium data of water+MEA were measured in the pressure range from 50.0 to 70.0 kPa and temperature range from 355.2 to 430.3 K. The measured data were correlated with the UNIQUAC and NRTL activity coefficient models.
Keywords: Vapor Liquid Equilibrium; Monoethanolamine; Water; Activity Coefficient; Thermodynamic Consistency
Effects of pH, salt type, and ionic strength on the second virial coefficients of aqueous bovine serum albumin solutions by YoonKook Park; Ginkyu Choi (193-198).
The osmotic pressures of aqueous bovine serum albumin (BSA) solutions were measured at different pH (3.6, 4.6, 5.6, and 7.6) in combination with different concentrations (0.01 M, 0.1 M, 1 M, and 3 M) of salts (sodium, pottasium, and lithum) by using a Wescor colloid membrane osmometer. The osmotic second virial coefficients for BSA were determined from the experimental osmotic pressure. Predominant forces between protein molecules were measured at the various pH, ionic strength, and type of salt. These experimental data were utilized to determine the depth of square-well potential, which accounts for specific interactions between protein molecules at various conditions.
Keywords: Second Virial Coefficients; Specific Interaction; SBA; Osmotic Pressure; PMF
Cloud point behavior for poly(isodecyl methacrylate)+supercritical solvents+cosolvent and vapor-liquid behavior for CO2+isodecyl methacrylate systems at high pressure by Sang-Eon Kim; Soon-Do Yoon; Ki-Pung Yoo; Hun-Soo Byun (199-205).
Experimental cloud-point data of binary and ternary mixtures for poly(isodecyl methacrylate) [P(IDMA)] in supercritical carbon dioxide, dimethyl ether (DME), propane, propylene, butane and 1-butene have been studied experimentally using a high pressure variable volume view cell. These systems show the phase behavior at temperature of 308 K to 473 K and pressure up to 255 MPa. The cloud-point curves for the P(IDMA)+CO2+isodecyl methacrylate (IDMA) are measured in changes of the pressure-temperature (P-T) slope, and with cosolvent concentrations of 0-60.1 wt%. Also, experimental data of phase behaviors for IDMA in supercritical carbon dioxide is obtained at temperature range of 313.2–393.2 K and pressure range of 5.8–22.03 MPa. The experimental results were modeled with the Peng-Robinson equation of state. The location of the P(IDMA)+CO2 cloud-point curve shifts to lower temperatures and pressures when DME is added to P(IDMA)+CO2 solution. The P(IDMA)+C4 hydrocarbons cloud-point curves are ca. 16.0 MPa lower pressures than the P(IDMA)+C3 hydrocarbons curves at constant temperature.
Keywords: High Pressure Phase Behavior; Poly(isodecyl methacrylate); Isodecyl Methacrylate; Supercritical Fluid Solvents; Cloud-point
Measurement of VLE data for propane+1,1-difluoroethane at various temperatures from 268.15 to 333.15 K by Gimyeong Seong; Ah Ram Kim; Ki-Pung Yoo; Jong Sung Lim (206-213).
Isothermal vapor-liquid equilibrium data for the binary systems of propane (R-290) (1)+1,1-difluoroethane (HFC-152a) (2) were measured at eight temperatures of (268.15, 273.15, 283.15, 293.15, 303.15, 313.15, 323.15 and 333.15 K), respectively. The experiments were performed with a circulation-type equilibrium apparatus to measure temperature, pressure, and the compositions of the liquid and vapor phases. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS) using the Wong-Sandler mixing rules and the Carnahan-Starling-DeSantis equation of state (CSD EoS). Calculated results showed good agreement with experimental data. It was found that this system has very strong positive azeotropes for all the temperature ranges studied here.
Keywords: Propane (R-290); HFC-152a; Vapor-liquid Equilibria (VLE); Carnahan-Staring-DeSantis Equation of State (CSD EoS); Peng-Robinson Equation of State (PR EoS)
Molecular modeling and experimental verification of lipase-catalyzed enantioselective esterification of racemic naproxen in supercritical carbon dioxide by Cheong Hoon Kwon; Jeong Yeong Jeong; Jeong Won Kang (214-219).
Experimental and simulation analyses were performed on the lipase-catalyzed esterification reaction of racemic naproxen by CALB (candida antarctica lipase B) enzyme in supercritical carbon dioxide. The reaction pathways were investigated by quantum mechanical analysis, and the enantioselectivity of the products was predicted by molecular dynamics simulation analysis. Calculated results from molecular modeling in supercritical carbon dioxide were qualitatively compared with experimental data by using racemic naproxen as a substrate. All molecular modeling results and experimental data were acquired and compared with those in ambient and supercritical condition. Moreover, to verify the stability of enzymatic reaction in each solvent condition, reaction pathways were investigated in several solvent conditions (vacuum, water, hexane and supercritical carbon dioxide), and the stability of enzymatic reaction in supercritical carbon dioxide was compared with other solvent conditions.
Keywords: Racemic Naproxen; Candida antarctica Lipase B; Enantioselectivity; Supercritical Carbon Dioxide; Quantum Mechanical Analysis; Molecular Dynamics Simulation
Measurement of excess enthalpies using a high-pressure flow microcalorimeter and determination of binary interaction parameters for thermodynamic models by Chae Ku Yi; YoonKook Park; Seong-Sik You (220-224).
While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the excess enthalpies of binary systems containing CO2 by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically, the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the Flory-Huggins interaction parameters of a binary mixture CO2 containing with various mole compositions were also estimated by employing high-pressure IMC.
Keywords: Equation of State; Isothermal Microcalorimetry (IMC); Peng-Robinson EOS; Flory-Huggins Interaction Parameter
A multi-fluid nonrandom lattice fluid model for mixtures containing nonionic surfactants by Sunghyun Jang; Moon Sam Shin; Hwayong Kim (225-229).
Surfactant systems show highly non-ideal phase behavior because of the inter-association and intra-association hydrogen bond. We present a lattice fluid equation of state that combines the multi-fluid nonrandom lattice fluid model with modified Veytsman statistics for intra+inter molecular association to calculate phase behavior for mixture containing surfactant systems. The literatureresults fitted to this model show good accordance for mixtures containing nonionic surfactant systems.
Keywords: Amphipiles; Lattice Model; Association Surfactants; Alkanes
Nonrandom lattice fluid group contribution parameter for vapor-liquid equilibrium of esters and their mixtures by Alexander Breitholz; Jong Sung Lim; Jeong Won Kang; Ki-Pung Yoo (230-234).
A group contribution version of the nonrandom lattice fluid equation of state (NLF-GC EOS) has been used to predict the vapor-liquid phase equilibria (VLE) of esters and their mixtures. The investigated esters were divided into groups according to the contribution scheme. Two different types of parameters were regressed from experimental datasets. Size parameters were fitted to pure component properties, and the group-group energy interaction parameters were simultaneously fitted to several binary mixture data sets. For systems containing propylene oxide, missing binary VLE data was predicted by using the COSMO-RS method. Parameters obtained by using the COSMO-RS method were later used to successfully predict experimentally measured binary propylene oxide+esters systems. The overall good prediction capability of the NLF-GC EOS could be proven for the investigated systems.
Keywords: COSMO-RS; Esters; Group Contribution; Nonrandom Lattice Fluid Equation of State
Modified Guggenheim-Huggins-Miller combinatorial factor and its application to lattice fluid equation of state by Ju Ho Lee; Moon Sam Shin; Hwayong Kim (235-239).
The Guggenheim-Huggins-Miller (GHM) combinatorial factor is modified by introducing a factor in the pair probability of a hole-hole pair. The proposed contribution is combined with the expanded quasi-chemical contribution and tested against saturated vapor pressure and liquid density. The proposed model correlates experimental saturated liquid density better than a quasi-chemical nonrandom lattice fluid (QLF) model based on original GHM combinatorial factor. The optimized parameters show a quite different behavior compared with that of the QLF model and the relationships between the parameters of two models are discussed.
Keywords: Combinatorial Factor; Equation of State; Guggenheim-Huggins-Miller; Lattice Fluid; Pair Probability
Correlation of measured excess enthalpies of binary systems composed of n-alkane+1-alkanol by Cheong Hoon Kwon; Jeong Won Kang (240-245).
The excess enthalpies of the binary mixture composed of n-alkane (n-octane, n-nonane, n-decane) and 1-alkanol (ethanol, 1-propanol, 1-butanol) have been measured by using a flow-type isothermal microcalorimeter (model CSC 4400, Calorimetry Science Corp., USA) at 313.15 K under atmospheric pressure. The measured excess enthalpy data were correlated by the Redlich-Kister equation and the nonrandom lattice fluid with hydrogen bonding (NLFHB) equation of state. Hydrogen bonding type specific parameters were introduced in the NLF-HB equation of state framework, and the effects of those parameters were investigated for excess enthalpy calculations. With two adjustable temperature-dependent interaction parameters, the NLF-HB equation represents the excess enthalpies for nine binary systems qualitatively.
Keywords: Excess Enthalpy; Isothermal Microcalorimeter; Equation of State; N-Alkane; 1-Alkanol; Redlich-Kister Equation
Solubility and growth rate of reactive blue49 and black8 dyes in salting-out system by Hyun Kak Han; Hyong-Ki Jung (246-249).
Reactive dyeing is one of most widely used methods for the coloration of cellulosic fibers. Reactive dyes have a low utilization degree compared to other types of dyestuff, since the functional group also bonds to water, creating hydrolysis. Salting out crystallization process was used to obtain dye crystals from solution. Physical properties and growth rate were measured for the design of the crystallization process. Density of RB8 crystal was 1.92 g/cm3 and that of RB49 was 1.26 g/cm3. Density of dye solution was linearly decreased with rise in temperature. Saturation solubility to the water was constant over room temperature. Solubility of dye solution was decreased by higher temperature and higher KCl concentration. The growth rate of RB8 was 0.964×10−06ΔC1.041 and that of RB49 was 2.922×10−06ΔC2.236 respectively.
Keywords: Solubility; Dye; Salting-out Crystallization; Density; Growth Rate
Electrochemical characteristics of Al-Mg alloy in seawater for leisure ship: Stress corrosion cracking and hydrogen embrittlement by Seong-Jong Kim; Min-Su Han; Seok-Ki Jang (250-257).
We investigated the mechanical and electrochemical properties of aluminum alloys. Aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al2O3 or Al2O3 · 3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl− ions destroy this passive film. The current density in the first passivity range during the application of anodic protection had a similar value as that for concentration polarization by dissolved oxygen during the application of cathodic protection. The current density in the first passivity range had the lowest value overall. The lowest current densities in the potentiostatic and galvanostatic tests occurred at potentials of −1.4 to −0.7 V and −0.9 to −0.7 V, respectively.
Keywords: Electrochemical Property; Aluminum Alloy; Corrosion; Seawater; Passivity; Cathodic Protection; Potentiostatic Test
Applications of silver nanoplates as colorimetric indicators of pH-induced conformational changes in cytochrome c by Junsu Park; Do-Young Yoon; Younghun Kim (258-260).
Silver nanoplates (AgNPs) were used as a colorimetric indicator of pH-induced conformational changes in the protein, cytochorme c (cyt c). Cyt c was covalently bound to the surface of AgNPs, and UV-vis spectroscopy was used to identify changes in the optical properties of the resulting cyt c-AgNP conjugates in colloidal solution over pH, with values ranging from 3.1 to 10.6. Transmission electron microscopy (TEM) results indicated that the morphological changes in cyt c-AgNP conjugates were dependent on pH. Moreover, pH-induced conformational changes in cyt c could be detected by visual inspection of the color changes in cyt c-AgNPs, which occurred as a result of the coupling effect of localized surface plasmon resonance (LSPR) by aggregated AgNPs.
Keywords: Silver Nanoparticle; Colorimetric; Cytochrome; pH
Synthesis of nanometer sized Bi2WO6s by a hydrothermal method and their conductivities by Dong Young Kim; Sujung Kim; Min-Kyeong Yeo; In-Gyung Jung; Misook Kang (261-264).
Nanometer-sized bismuth tungsten oxides, Bi2WO6s, were successfully synthesized by hydrothermal treatment at 200 °C for 24 hr, and their morphologies and crystallite sizes were influenced by adjusting the conditions to pH 4, 7, and 9. TEM images revealed that the particles were sheet-shaped and the crystallite sizes ranged from 7–120 nm. The samples absorbed in the visible range at about 380–400 nm. The lowest conductivity, 1.0×106 ohm/square, was observed for Bi2WO6 prepared at pH 4 with a 150 nm film thickness. As the annealing temperature for Bi2WO6 prepared at pH 7 was increased, the conductivity decreased due of formation of larger particles by coagulation and sintering at high temperatures. Conductivity appears to improve with increasing film thickness up to 1,500 nm.
Keywords: Nanometer-sized Bismuth Tungsten Oxide; Hydrothermal Treatment; pH; Conductivity
Thin film silver deposition by electroplating for ULSI interconnect applications by Joon-Mo Seo; Sung Ki Cho; Hyo-Chol Koo; Soo-Kil Kim; Oh Joong Kwon; Jae Jeong Kim (265-268).
Ag seed layers were pretreated with 1: 1,000 diluted nitric acid cleaning solution for 60 s to obtain a clean and oxide-free Ag surface. When an applied potential was less than −800 mV in Ag electroplating, the deposition rate was over 2,000 Å/min and the resistivity of Ag deposit was 1.80 μΩ·cm. But the deposit film became rougher with a negative increase in the potential, and it was also observed through measuring the double layer capacitance. The resistivity of Ag film annealed at 350 °C for 30 min was decreased from 1.80 μΩ·cm to 1.67 μΩ·cm and the agglomeration of Ag grains was not observed on the surface of the annealed Ag films. To reduce the surface roughness, thiourea was added in the electrolyte and it was decreased below 15 nm.
Keywords: ULSI Interconnection; Ag; Electroplating
Brownian diffusion effect on nanometer aerosol classification in electrical mobility spectrometer by Panich Intra; Nakorn Tippayawong (269-276).
A multi-channel differential mobility analyzer (MCDMA) or aerosol spectrometer is widely used for classifying and measuring nanometer aerosol particles in the size range from 1 nm to 1 μm because of its better time response than a typical differential mobility analyzer. In the present study, the effect of Brownian diffusion on electrical mobility classification and trajectory of nanometer aerosol particles in an electrical mobility spectrometer developed at Chiang Mai University has been analytically investigated. Th Brownian diffusion of particles inside the spectrometer increased with decreasing particle size and flow rates of aerosol and clean sheath air, and with increasing inner electrode voltage, and also decreased with decreasing operating pressure. The particle trajectories considering Brownian diffusion motion inside the spectrometer were found to be broader than those under no Brownian diffusion. Smaller particles were found to have higher degree of broadening of trajectory than the larger particles. Brownian diffusion effect was found to be significant for particles smaller than 10 nm.
Keywords: Brownian Diffusion; DMA; Electrical Mobility; Nano-aerosol
Enhanced light emission of nano-patterned GaN via block copolymer thin films by Yo-Han Cho; Kyunghee Lee; Kyunghoon Kim; Kwang Hyun Baik; Jinhan Cho; Jihyun Kim; Kyusoon Shin; Joona Bang (277-280).
We demonstrate that the nanoscopic block copolymer patterns on GaN can enhance light extraction efficiency of GaN-based light emitting diodes. Nanoporous patterns were fabricated on a bare GaN substrate via self-assembly of poly(styrene-b-methyl methacrylate) block copolymers from which PMMA microdomains were selectively removed later on. A bare GaN surface was treated with a photo-crosslinkable thin layer of poly(styrene-r-methyl methacrylate) random copolymers to tune the cylindrical microdomain orientations. The nanoporous block copolymer thin film was controlled to be thicker than its typical repeat period in bulk by incorporating PMMA homopolymer into block copolymer. Consequently, the light extraction efficiency in photoluminescence spectra could be tuned with the thickness of nanopatterned thin film on GaN.
Keywords: GaN; Light Emitting Diodes; Block Copolymers; Nanoporous Templates
Synthesis and characterization of high purity aluminum sec-butoxide from aluminum dross by Seung-Joon Yoo; Dong-Heui Kwak; Se-Il Lee; Jae-Wook Lee; Un-Yeon Hwang; Jin-Geol Kim; Heung-Jo Jung; Ho-Sung Yoon; Hee Dong Jang (281-284).
Aluminum sec-butoxide (ASB) was synthesized to a high purity grade from Al dross through dissolution reaction and vacuum distillation under the condition of 3 mol C4H9OH/mol Al as a stoichiometric reactant ratio and 10−3 mol HgI2/mol Al as a catalyst. The dissolution reaction proceeded for 24 hours, then pure ASB was recovered by vacuum distillation from the Al solution obtained after the dissolution. The ASB thus synthesized was quantitatively analyzed by a complexometric method for purity. This reaction gave a 99.2% purity and 28% yield. Characteristics of the synthesized ASB were analyzed by FT-IR, 27Al-NMR, and 1H-NMR. The result of analysis revealed that the crystalline structure between the synthesized ASB and commercial ASB was identical. Especially, the yield synthesized through this experiment corresponded to the total amount of Al metal existing in Al dross.
Keywords: Al Dross; Dissolution; Vacuum Distillation; High Purity; Aluminum Sec-butoxide
Electrical characterizations of Neutron-irradiated SiC Schottky diodes by Geunwoo Ko; Hong-Yeol Kim; Joona Bang; Jihyun Kim (285-287).
Neutrons with an average energy of 9.8±0.8 MeV were irradiated onto silicon carbide Schottky diodes. After bombardment at a fluency of 2.75×1011 neutron/cm2, the Schottky barrier height, ideality factor, and the leakage currents remained unchanged. The electrical properties began to deteriorate after bombardment at a fluency of 5.5×1011 neutron/cm2. In this study, we demonstrate that SiC SBD is robust under neutron irradiations and is well suited for space operations up to bombardments at a fluency of 2.75×1011 neutron/cm2.
Keywords: Neutron Irradiation; Silicon Carbide; Diode
Hydrodynamic characteristics of a horizontal flow ejector in a rectangular chamber by Og Sin Kim; Yoong Lee; Dong Hyun Lee (288-294).
The effects of the volumetric flow rate of primary motive water, water height, and the geometric parameters of the hydrodynamiccharacteristics of the gas suction rate and gas phase holdup were investigated in a rectangular chamber (0.22×0.26×1.2 m-high) with a horizontal flow ejector. Gas suction rate increased with increasing volumetric flow rate of the primary motive water, mixing tube length and diffuser length, but it decreased with increasing water height and nozzle diameter. The gas phase holdup was directly proportional to gas suction rate, indicating its corresponding increase with the volumetric flow rate of the primary motive water. Conversely, it decreased with increasing water height and nozzle diameter. However, the mixing tube length affected the gas phase holdup minimally compared to other operating parameters. Both the gas suction rate and gas phase holdup correlated with the dimensionless equations of operating parameters.
Keywords: Gas Suction Rate; Gas Phase Holdup; Horizontal Flow; Ejector; Rectangular Chamber
Enthalpy profile-cure state relationship of compounded rubber by differential scanning calorimetry by Kyo-Chang Choi; Eun-Kyoung Lee; Sei-Young Choi (295-299).
Differential scanning calorimetry (DSC) was applied to natural rubber (NR) and NR/recycled natural rubber (RNR)(NR/RNR) blend to understand and optimize the state of cure, which is based on the value of the exothermic reaction obtained in process of vulcanization. Swelling and mechanical data were investigated with the increase of cure time from 15 to 35 minutes with an interval of 5 minutes and compared with the DSC enthalpy data. With the increasing cure time, cure enthalpy was decreased and a negative, while cure enthalpy was a positive value in 35-NR and 35-NR/RNR when cure time was over 35 minutes due to the reversion. Swell index (Si) was gradually decreased but increased slightly in the case of both NR and NR/RNR cured for 35 minutes. The study also indicated that cure enthalpy data was very precise and fast to predict the cure state of the NR and NR/RNR blend.
Keywords: Recycled Natural Rubber; Exothermic Reaction; Vulcanization; Cure Enthalpy
A comparative study of particle size analysis in fine powder: The effect of a polycomponent particulate system by Heekyu Choi; Woong Lee; Dong-Uk Kim; Shalendra Kumar; Jonghak Ha; Seongsoo Kim; Jungeun Lee (300-305).
We report the particle size distribution of poly component particulate systems studied in three kinds of experimental methods. Six analyzers, such as Mastersizer Microplus (Malvern Instruments Ltd., UK), LS230 (Coulter Electronics Ltd., USA) LMS30 (Seishin, Japan), Analysette22 (Fritsch, Germany), HELOS (Sympatec, Germany) based on a laser diffraction and scattering method, and the SKC-2000S (Seishin Co., Ltd., Japan) based on the centrifugal sedimentation method, were used to study the particle size distribution. The results do not show reasonably good agreement between the different analyzers and different sample systems. There is a discrepancy regarding the absolute values, which can be explained by the fact the techniques used are based on different measuring principles. The results of the present study reflect that the investigator must carefully select the particle size analyzer for a particular application. Therefore, we suggest that it is necessary to measure the particle size distribution by using at least two types of analyzers or more of different makers.
Keywords: Laser Scattering and Diffraction; Particle Size Analysis; Polycomponent Particulate System