Korean Journal of Chemical Engineering (v.27, #6)
Design of particles by spray pyrolysis and recent progress in its application by Dae Soo Jung; Seung Bin Park; Yun Chan Kang (1621-1645).
Spray pyrolysis is a promising aerosol process to produce “designer particles” of precisely controlled morphology with decorations on surfaces or inside particles. Need of precise control of properties has sparked researches on aerosol process that may replace conventional processes such as solid state reaction process or liquid precipitation method. However, productivity is the biggest obstacle in the development of a commercial scale process because the aerosol process is essentially operated at low particle concentration compared to liquid phase processes. In this review, by reviewing publications for the last 10 years we discuss how researchers on spray pyrolysis circumvent this inherent limitation of the aerosol process. First, the process of particle design by spray pyrolysis is introduced. Some key criteria are explained for selecting each component of spray pyrolysis: precursor, additive, carrier gas, heat source, and reactor type. Second, key contributions of major groups in Korea, Japan, Europe, and America are described. Third, some of named processes to overcome productivity of spray aerosol process are introduced. Fourth, applications of spray pyrolysis to materials related to alternative energy, environmental cleaning, information processing and display, and biomaterials are considered. Finally, future prospects of spray pyrolysis are discussed along with current standing issues for further progress of spray pyrolysis.
Keywords: Spray Pyrolysis; Nanoparticle; Aerosol; Atomizer; Surface Modification
A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion by Behnam Nikkhahi; Mehrzad Shams; Masoud Ziabasharhagh (1646-1653).
During transonic flow of steam in divergence nozzles, flow first supercools and then nucleates to become two-phase droplet flow. This phenomenon especially occurs in the last stages of steam turbines and affects performance. In this research, a numerical scheme for two-phase flow in nozzle passages is developed. An Eulerian-Eulerian reference frame is used for both phases. The shear stress transport turbulence model is used to model the Reynolds stresses appearing in the averaged Navier-Stokes equations. The homogeneous nucleation model is applied for the mass transfer in the transonic conditions. In this paper three nozzles with different rate of expansion are employed to be under study. Overall pressure ratio (static to total pressure) and droplet size are compared with the experimental data and good agreements are observed.
Keywords: Nucleation; Two-phase Flow; Nozzles; CFD; Eulerian-Eulerian
Automatic verification of operating schedules for batch processes using symbolic model checking: Latch model vs. real-time by Jinkyung Kim; Il Moon (1654-1661).
This study proposes two models for reading Gantt charts and finding embedded errors in the operating schedules of batch processes. Two automatic techniques for finding errors, a real-time model and a latch model, are developed using the symbolic model verifier (SMV) and are compared to verify that the schedules are error free and to represent the scheduling information and policies. These models are designed to automatically detect embedded errors relating to unavailability, superimpositions, and violation of intermediate storage policies in batch processes with various intermediate storage policies.
Keywords: Operating Schedule; Real-time Model; Latch Model; SMV; Batch Process
Prediction of the melt flow index using partial least squares and support vector regression in high-density polyethylene (HDPE) process by Tae Chang Park; Tae Young Kim; Yeong Koo Yeo (1662-1668).
In polyolefin processes the melt flow index (MFI) is the most important control variable indicating product quality. Because of the difficulty in the on-line measurement of MFI, a large number of MFI estimation and correlation methods have been proposed. In this work, mechanical predicting methods such as partial least squares (PLS) method and support vector regression (SVR) method are employed in contrast to conventional dynamic prediction schemes. Results of predictions are compared with other prediction results obtained from various dynamic prediction schemes to evaluate predicting performance. Hourly MFIs are predicted and compared with operation data for the high density polyethylene process involving frequent grade changes. We can see that PLS and SVR exhibit excellent predicting performance even for severe operating situations accompanying frequent grade changes.
Keywords: Melt Flow Index; Partial Least Square; Support Vector Regression; Prediction
Development of polyethylene melt index inferential model by Tae Young Kim; Yeong Koo Yeo (1669-1674).
In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of the difficulty in the on-line measurement of MI, a large number of MI estimation and correlation methods have been proposed. In this work, we propose a new MI predicting model in which the reaction heat term in existing prediction models is replaced by temperature. The proposed model is compared with other prediction models as well as operating data to evaluate MI predicting performance. The present model shows least predicting errors compared to existing models.
Keywords: Polymerization Reactor; Polyethylene; Melt Index Prediction; Reaction Heat
Data-driven prediction model of indoor air quality in an underground space by Min Han Kim; Yong Su Kim; JungJin Lim; Jeong Tai Kim; Su Whan Sung; ChangKyoo Yoo (1675-1680).
Several data-driven prediction methods based on multiple linear regression (MLR), neural network (NN), and recurrent neural network (RNN) for the indoor air quality in a subway station are developed and compared. The RNN model can predict the air pollutant concentrations at a platform of a subway station by adding the previous temporal information of the pollutants on yesterday to the model. To optimize the prediction model, the variable importance in the projection (VIP) of the partial least squares (PLS) is used to select key input variables as a preprocessing step. The prediction models are applied to a real indoor air quality dataset from telemonitoring systems data (TMS), which exhibits some nonlinear dynamic behaviors show that the selected key variables have strong influence on the prediction performances of the models. It demonstrates that the RNN model has the ability to model the nonlinear and dynamic system, and the predicted result of the RNN model gives better modeling performance and higher interpretability than other data-driven prediction models.
Keywords: Air Quality Prediction; Nonlinear Modeling; Recurrent Neural Networks (RNN); Predicted Model; Partial Least Squares (PLS); Subway Station
Modeling supply chain operations as multi-level programming problems and their parametric programming based computation methodology by Jun-Hyung Ryu (1681-1688).
This paper proposes a modeling methodology for supply chain operations with a focus on the relationships of supply chain entities. Supply chain operation problems are mathematically formulated into a multilevel programming problem. A multiparametric programming-based computation methodology is proposed to compute the solution of the problems. Numerical examples are presented to illustrate the proposed modeling and computational methodology with some remarks.
Keywords: Supply Chain; Relationship; Modeling; Parallel; Sequential; Multilevel Programming; Parametric Programming
Enhancement of oxygen reduction activity by sequential impregnation of Pt and Pd on carbon support by Dohwa Jung; Sangchul Beak; Kee Suk Nahm; Pil Kim (1689-1694).
Two Pd-based PtPd bimetallic catalysts (mole ratio of Pt to Pd=1: 18) were prepared by co-impregnation (Pt-Pd/C) and sequential impregnation of Pt on Pd/C [Pt(Pd/C)] for the application to oxygen reduction reaction (ORR). The prepared bimetallic catalysts had lower ORR activities than Pt/C, while they showed largely enhanced activity compared to Pd/C. In particular, the extent of enhancement was found to be dependent on the surface composition. The observed mass and specific activities of Pt(Pd/C) were more than two times higher than those of Pt-Pd/C. The superior activity of Pt(Pd/C) observed from the performed studies was attributed to its Pt-rich surface.
Keywords: Oxygen Reduction Reaction (ORR); Pd Catalyst; Pt Catalyst; Bimetallic Catalyst; Polymer Electrolyte Fuel Cells (PEMFCs)
Simple one-pot synthesis of a mesoporous superacidic catalyst for the dehydration of glycerol to acrolein by Lina Yang; Ji Bong Joo; Nam Dong Kim; Kwang Seop Jung; Jongheop Yi (1695-1699).
Mesoporous silica containing a ZrO2/SO 4 2− superacid catalyst (SZS) was synthesized via a simple one-pot process. ZrO2/SO 4 2− (SZ) was introduced during the synthesis of the SBA-15. When the molar ratio of Zr to Si was less than 0.37 : 1, a 2D-hexagonal pore structure was maintained. The superacidic SZ was successfully supported on mesoporous silica resulting in superacidity. The prepared SZS catalysts were applied to the conversion of glycerol to acrolein by dehydration and had considerable catalytic activity. The present study describes the first attempt to utilize mesoporous silica-supported superacid catalysts in the dehydration of glycerol to produce acrolein.
Keywords: Mesoporous Silica; ZrO2/SO 4 2− ; One-pot Synthesis; Superacid; Acrolein
Reaction kinetics of phenol synthesis through one-step oxidation of benzene with N2O over Fe-ZSM-5 zeolite by Guanjie Mi; Jianwei Li; Jie Zhang; Biaohua Chen (1700-1706).
Based on the information from GC-MS on-line measurement and thermodynamic analysis, the reaction network of gas-phase hydroxylation of benzene with nitrous oxide over Fe-ZSM-5 zeolite was systematically investigated. The main reactions and side reactions were identified, and a kinetic reaction network was proposed as follows: benzene+N2O→phenol→CO/CO2. According to the mechanism, the experimental results were interpreted reasonably. The hydroxylation kinetic experiments were carried out in an isothermal integral microreactor under the conditions of n(benzene)/n(N2O)=8–12, T=663–763 K and atmospheric pressure. Based on the reaction network proposed, the parameters in the rate model of power-law were estimated by means of Gauss-Newton optimal method with the Levenberg-Marquardt modifications, and the results were in good agreement with the experimental data.
Keywords: Benzene; N2O; Phenol; Oxidation; Reaction Kinetics; Reaction Network; Fe-ZSM-5 Zeolite
Reasearch on the main factors for changes in pressure based on turbulent circulating fluidized bed coal gasification technology by Duan Feng; Bao-Sheng Jin; Ya-Ji Huang; Bin Li; Yu Sun; Yiming Wu; Ming-Yao Zhang (1707-1714).
High temperature preheated air and steam as gasifying agent and coal gasification was performed in a pressurized turbulent circulating fluidized bed (CFB) gasification pilot plant to investigate the pressurized gasification process and estimate its potential. Within the scope of this paper this test facility as well as its operation behavior was described. Furthermore, the parameter pressure has been investigated regarding its influence on the syngas composition and was presented and discussed in the following. The results show that the gasification quality is improved at higher pressure because of the better fluidization in the reactor. Coal gasification at a higher pressure shows advantages in lower heat value and carbon conversion. With the gasifier pressure increased from 0.1MPa to 0.3MPa, the gas heating value is increased by 15%. Increasing the gasifier pressure would increase the carbon conversion from 57.52% to 76.76%. Also, the dry gas yield and efficiency of cold gas increase little with the increase of the gasifier pressure. The operating parameter of pressure exists at optimum operating range for this specific CFB coal gasification process.
Keywords: Circulating Fluidized Bed; Gasification; Pressurized; Bituminous
Effect of non-steam component of steam-hydrogasifier product gas upon sulfidation of zinc oxide sorbent by Kiseok Kim; Nokuk Park (1715-1717).
Sulfidation of zinc oxide sorbent by desulfurization of steam-hydrogasifier product gas was affected by non-steam components of the reactant gas in a complicated manner. Relative abundance of each component appeared to shift the reaction equilibrium toward ZnO sulfidation, thereby enhancing the extent of sorbent utilization for sulfur removal, while their respective contributions were not simply additive toward the overall increase of sulfur capture capacity of the sorbent. This subtle outcome will have to be further investigated by varying, respectively, the individual abundance of each non-steam component as well as H2S content of the reactant gas to be desulfurized.
Keywords: Sulfidation; Zinc Oxide; Sorbent; Hydrogen Sulfide
Design, construction and operation of lab scale cylindrical steam assisted gravity drainage model for heavy oil recovery by Nansuk You; Songhun Yoon; Wonkyu Lee; Heung Yeoun Lee; Sang-Yeop Park; Jae Heon Shim; Jong Soo Kim; Chul Wee Lee (1718-1724).
Based on a theoretical background [1,2], a lab scale cylindrical SAGD (steam assisted gravity drainage) model was designed, constructed and operated. There are six different parts in the apparatus: (1) water supplier, (2) steam generator, (3) SAGD cylindrical model, (4) cooling system, (5) constant pressure maintaining system and (6) production system. Temperature, pressure and steam injection rate were controlled by computer, and product (mixture of oil and water) was collected/separated manually. Extra heavy oil (<10 cp at 200 °C) and glass bead (diameter 1.5 mm) were mixed homogeneously for making porosity of 0.3 and applied for simulating oil sand. For obtaining optimum operation conditions of SAGD apparatus, several attempts were made. When the steam at high temperature (160–180 °C), high pressure (8–9 atm) was injected with 20–25 cc/min, cSOR (cumulative steam to oil ratio) of about 5 was obtained with oil recovery of 78.8%.
Keywords: Oil Sand; Bitumen; SAGD Model; Scaling Factor; SOR (Steam to Oil Ratio)
Optimization of medium components for D-ribose production by transketolase-deficient Bacillus subtilis NJT-1507 by Ting Fang; Xiaochun Chen; Nan Li; He Song; Jianxin Bai; Jian Xiong; Hanjie Ying (1725-1729).
Statistical experimental designs were used to optimize the composition of culture media for the production of D-ribose by Bacillus subtilis. A fractional factorial design 2(5-2) was used to determine medium components that significantly affected D-ribose production. The concentrations of glucose and (NH4)2SO4 were the significant factors. Central composite design and response surface methodology were then used to estimate the quadratic response surface and determine the factor levels for maximum production of D-ribose. Finally, the optimal medium composition was obtained (g/L): glucose, 172.75; (NH4)2SO4, 13.2; yeast powder, 4; corn steep liquor, 8 and MnSO4, 0.5. This optimization strategy increased D-ribose production from 73.21 g/L to 88.57 g/L, an increase of 22% compared with the original conditions. The D-ribose production yield to glucose concentration was also enhanced from 0.37 g/g to 0.52 g/g. Confirmatory experiments were also performed to demonstrate the accuracy of the model. Under the optimal medium using ammonia to control pH in a 5 L fermenter, the D-ribose yield was increased to 95.28 g/L after 3 days of cultivation at 37 °C.
Keywords: Bacillus subtilis ; D-ribose; Fermentation; Medium Optimization; Response Surface Methodology
An on-line infrared spectroscopic system with a modified multipath White cell for direct measurements of N2O from NH3-SCR reaction by Dong Woo Kim; Moon Hyeon Kim; Sung-Won Ham (1730-1737).
An on-line, continuous IR-based N2O measurement system has been developed by combining with a variable multipath “White cell” to avoid a huge amount of the well-known artifact errors in actual N2O concentrations determination when analyzing grab samples taken from stationary sources, such as fossil fuel-fired power plants. For solving the problems confronted in earlier stages of this study, the gas cell had to have modifications of the feed through of gas sample flows, the multilayer coatings of stainless steel mirrors, and the thermal efficiency to provide high cell inner temperatures in flowing gas samples. These modifications allow good tolerance of the gas cell to gases and chemicals, such as NO x and NH3, and NH4NO3 driven from them, and its usage for a long lifetime even under harsh conditions. They also offer excellent performance not only in directly determining the extent of N2O formation during the course of NH3-SCR reaction over a sample of a commercial V2O5-WO3/TiO2 catalyst, but also in simultaneously monitoring changes in concentrations of NO, NO2 and NH3 during the reaction. Each reference peak was chosen in gasphase spectra for N2O, NO x , NH3 and H2O, and CO2 as a possible interference, and the modified gas cell was finely tuned to obtain their spectra with a high resolution under optimal operating conditions. The catalyst gave significant amounts of N2O formation at reaction temperatures greater than 350 °C, and attention should be paid to the possibility of N2O production from commercial NH3-SCR deNO x processes with V2O5/TiO2-based catalysts.
Keywords: Long Path White Cell; On-line N2O Measurements; Commercial V2O5-WO3/TiO2 Catalysts; NH3-SCR Reaction; N2O Formation
IR study on the reduction of NO and NO2 by hydrazine monohydrate over Fe-BEA zeolite by Se Min Park; Gon Seo; Young San Yoo; Hyun-Sik Han (1738-1743).
The adsorption of NO and NO2 and their subsequent reduction by hydrazine monohydrate (HDM) over Fe-BEA zeolite were investigated using an FT-IR spectrophotometer equipped with an in-situ cell. Although NO and NO2 molecules were adsorbed on Fe species in an unaltered state, some of them reacted with oxygen atoms, resulting in the adsorption of NO2 and NO 3 − , respectively. The reducing species that had originated from HDM on Fe-BEA selectively reduced these molecules to N2, while a small amount of N2O was formed in the reduction of NO by HDM. NO and NO2 were rapidly reduced by HDM through their adsorbed state even at 150 °C, and Fe species were required for their adsorption and for the formation of reducing species from HDM.
Keywords: Hydrazine Monohydrate; Fe-BEA Zeolite; NO x
Kinetics studies of dimethyl carbonate synthesis from urea and methanol over ZnO catalyst by Junliang Zhang; Feng Wang; Wei Wei; Fukui Xiao; Yuhan Sun (1744-1749).
A kinetic experiment of dimethyl carbonate (DMC) synthesis by urea methanol over ZnO catalyst was carried out in an isothermal fixed-bed reactor. A kinetic model based on the mole fraction was proposed and the kinetic parameters were estimated from the experimental results. The model predictions were compared with the experimental data and fair agreements were found. The effects of the reaction temperature (443–473 K), space time (0–4.7 h mol−1 kg cat ) and urea mass percent (5–9%) in feed on DMC mole fraction were investigated. It was found that the reactions are mainly influenced by the reaction temperature and space time rather than urea mass percent in feed. The experimental and simulated results indicated that the reaction from MC to DMC was the rate-controlling step in the DMC synthesis process from urea and methanol. It is important to remove the DMC and byproduct ammonia to achieve a high selectivity of DMC. This implies that reactive distillation might be used in the DMC synthesis on an industrial scale to achieve a higher selectivity of DMC.
Keywords: Kinetics; Dimethyl Carbonate; Methanol; Urea
Kinetic correlation between degradation and dechlorination of perchloroethylene in the Fenton reaction by Hee-Sik Kim; Wan-Suk Lee; Chi-Yong Ahn; Byung-Hyuk Kim; Jang-Eok Kim; Hee-Mock Oh (1750-1754).
In the Fenton reaction, degradation and dechlorination are directly affected by the concentrations of hydrogen peroxide and Fe3+. Although there is considerable research on the biodegradation of chlorinated compounds combined with the Fenton reaction, the kinetics of degradation and dechlorination of the reaction, with various concentrations of hydrogen peroxide and Fe3+, have been rarely investigated. Therefore, we investigated the degradation and dechlorination of PCE with various concentrations of hydrogen peroxide and Fe3+. The initial concentration of PCE (10 μM) decreased from a value of 8.9 μM (with 0.1 mM of hydrogen peroxide and 5 mM of Fe3+) to 1.1 μM (with 10 mM of hydrogen peroxide and 5 mM of Fe3+); the respective values for chloride ions produced were 0.9 and 21.6 μM. Also, the initial 10 μM of PCE decreased from 8.9 (with 0.1 mM of Fe3+ and 5 mM of hydrogen peroxide) to 2.2 μM (with 10mM of Fe3+ and 5 mM of hydrogen peroxide); the respective chloride ions produced were 0.7 and 14.5 μM. The logarithmic correlations between the degradation and dechlorination coefficients were 0.7682 and 0.7834 for concentrations of hydrogen peroxide and Fe3+, respectively. Both coefficients were used, from all possible cases, to derive six models which displayed both the ratio of degradation and dechlorination and the hydrogen peroxide and Fe3+ concentrations. The dechlorination of PCE could then be predicted with the model obtained by the coefficient with the concentration of hydrogen peroxide and Fe3+. The models could be applied to various Fenton reactions for optimization of degradation or dechlorination, such as biodegradation of PCE which is scarcely degraded by aerobic bacteria.
Keywords: Dechlorination Value; Degradation; Fenton Reaction; Kinetic Correlation; Perchloroethylene (PCE)
Production of middle distillate through hydrocracking of paraffin wax over NiMo/TiO2-SiO2 catalysts by Joongwon Lee; Sunhwan Hwang; Sang-Bong Lee; In Kyu Song (1755-1759).
Titania-silica (TS(X), X=19, 26, 55, 70, and 79) supports with different titania content (X, wt%) were prepared by a precipitation method. NiMo/TS(X) catalysts prepared by an incipient wetness method were then applied to the production of middle distillate through hydrocracking of paraffin wax. Successful formation of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts was confirmed by ICP-AES and XRD measurements. NH3-TPD experiments were conducted to measure the acid property of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts. It was revealed that acidity of the catalyst played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to acidity of the catalyst. Among the catalysts tested, NiMo/TS(26) retaining moderate acidity showed the highest yield for middle distillate.
Keywords: Hydrocracking; Middle Distillate; Titania-silica; Acid Property; NiMo Catalyst
Optimization of methanol synthesis reaction on Cu/ZnO/Al2O3/ZrO2 catalyst using genetic algorithm: Maximization of the synergetic effect by the optimal CO2 fraction by Hye-Won Lim; Hye Jin Jun; Myung-June Park; Hyo-Sik Kim; Jong Wook Bae; Kyoung-Su Ha; Ho-Jeong Chae; Ki-Won Jun (1760-1767).
A kinetics model that takes the synergetic effect of carbon dioxide fraction on the methanol production rate into account is applied to the development of a mathematical model for the bench-scale reactor. A comparison between the simulation results and the experimental data corroborates the validity of the model. Several optimization strategies are suggested to maximize the methanol yield, among which the utilization of piecewise trajectories for wall temperature along the reactor axis as well as the optimal CO2 fraction at the inlet of the reactor is found to be the best strategy in the sense of methanol production per unit amount of the feed, in such a way that the optimization strategy considers the variation of the reaction temperature in the reactor and maximizes the synergetic effect on the production rate by the addition of carbon dioxide.
Keywords: Methanol; Mathematical Model; Bench-scale Reactor; Cu-based Catalyst; Optimization; CO2 Fraction
Catalytic degradation of high-density polyethylene over SAPO-34 synthesized with various templates by Jong Hwa Park; Hyeon Su Heo; Young-Kwon Park; Kwang-Eun Jeong; Ho-Jeong Chae; Jung Min Sohn; Jong-Ki Jeon; Seung-Soo Kim (1768-1772).
A variety of SAPO-34 catalysts were prepared using various templates, such as tetraethylammonium hydroxide (TEAOH), diethylamine (DEA), and a mixture of TEAOH and DEA, and then applied for the first time to the pyrolysis of high-density polyethylene (HDPE). The crystal morphology and physicochemical properties were affected by the type of template employed. In particular, an inexpensive SAPO-34 catalyst, with good crystal properties and catalytic performance, was obtained using a mixed-template of DEA and TEAOH. Through N2 isotherm, XRD, SEM and NH3 TPD the effects of the mixed-template on the crystal morphology and acidity were investigated. The catalytic activity of SAPO-34 in the pyrolysis of HDPE was improved with the use of a mixed-template, due to the crystal size, surface area and acidity.
Keywords: SAPO-34; High Density Polyethylene; Mixed-template; Crystal Morphology
Simulation of methanol-to-olefin reaction over SAPO-34 catalysts with different particle sizes: Formation of active sites and deactivation by Hag Geum Kim; Kwang Young Lee; Hoi-Gu Jang; Yo Soon Song; Gon Seo (1773-1779).
Conversion profiles of methanol-to-olefin (MTO) reaction over SAPO-34 catalysts with different particle sizes were simulated using two kinetic models. The MTO reaction was assumed to consist of three steps: the formation of hexamethylbenzene (HMB), the production of lower olefins over HMB and the further condensation of HMB to polyaromatic hydrocarbons. To reflect the effect of particle size on the MTO reaction, only the space near the external particle surface was considered to be available for HMB formation in Model I, whereas an effectiveness factor and a deactivation function were introduced in Model II. The simulated conversion profiles of the MTO reaction by both models successfully confirmed the presence of an induction period and deactivation, but Model II showed a better agreement between the experimental and simulated results because of its inclusion of the deactivation function and its consideration for the gradient of methanol concentration.
Keywords: MTO Reaction; SAPO-34; Particle Size; Induction Period; Deactivation; Simulation
A comparative study on the laser removal of Cs+ ion from type 304 stainless steel by Hui-Jun Won; Byambatseren Baigalmaa; Jei-Kwon Moon; Chong-Hun Jung; Kune-Woo Lee (1780-1785).
A Q-switched Nd:YAG laser with a 1,064 nm and 450 mJ/pulse was employed to study the cleaning characteristics of Type 304 stainless steel specimens artificially contaminated with Cs+ ions. Before laser irradiation, the specimens were treated with KCl and KNO3, respectively. The relative atomic molar percent of Cs+ ion on a metal surface was analyzed by EPMA. Before and after the laser irradiation, the morphology of the metal surfaces was investigated by SEM. The optimum laser fluence determined in the experimental range was 57.3 J/cm2. For all the test specimens, more than 95% of the Cs+ ions were removed by the application of 40 laser shots at 57.3 J/cm2. Cs+ ion removal efficiency was improved by the addition of nitrate ions to the contaminated metal surface. Surface temperature during the laser irradiation was calculated using Hertz-Knudsen equation to investigate the surface characteristics. A portion of particulates generated during the laser irradiation was found to accumulate around a crater of the specimen treated with the KCl solution. It was concluded that the ablated Cs+ ions formed an oxide after thermal activation on the surface and deposited on a metal surface for the KCl system. The higher Cs+ ion removal efficiency of the KNO3 system was attributed to the decomposition of the nitrate ions at a relatively low temperature and the easy reaction of the Cs+ ions with the oxygen generated from the decomposition of nitrate ions.
Keywords: Laser; Cleaning; Cs+ ; Nitrate; Chlorine; Hertz-Knudsen
Chemical reactivity of oxide materials with uranium and uranium trichloride by Sung Ho Lee; Choon Ho Cho; Yoon Sang Lee; Han Soo Lee; Jeong-Guk Kim (1786-1790).
A graphite crucible is used for the manufacturing of uranium ingots in the uranium casting equipment of the electrorefining process. Uranium and uranium alloys are typically induction melted in graphite crucibles under a vacuum condition; however, due to the chemical reactivity of uranium and most alloying elements with carbon, a protective ceramic coating is generally applied to the graphite crucibles. To investigate the most suitable ceramic coating material for application to graphite melting crucibles used for the melting uranium in uranium casting equipment, firstly, a thermodynamic analysis using HSC software was performed to examine the chemical reactivity of ceramic oxide materials with uranium and uranium trichloride, and also, experiments concerning the reactivity of molten uranium in some ceramic coated crucibles were performed at 1,300 °C. From the results, yttria was finally selected as the most suitable ceramic coating material for application to graphite crucibles for melting the uranium.
Keywords: Reactivity; Uranium; Yttria; Ceramic Materials; Graphite Crucible
Production and characterization of biodiesel from trap grease by Ji-Yeon Park; Jin-Suk Lee; Zhong-Ming Wang; Deog-Keun Kim (1791-1795).
The feasibility of the production of biodiesel from trap grease containing 51.5% free fatty acids (FFAs) was investigated. The esterification of FFAs by an acid catalyst followed by the transesterification of triglycerides by an alkali catalyst was examined. The esterification of trap grease by sulfuric acid as a homogeneous catalyst or by Amberlyst-15 as a heterogeneous catalyst was optimized through a response surface methodology. After the two-step esterification of trap grease by sulfuric acid, the acid value decreased from 102.9 mg KOH/g to 2.75 mg KOH/g. Through the transesterification by potassium hydroxide, fatty acid methyl ester (FAME) content reached 92.4%. Following the esterification of trap grease by Amberlyst-15, the acid value decreased to 3.23 mg KOH/g. With the transesterification by potassium hydroxide, FAME content increased to 94.1%. After the distillation of the produced biodiesel, FAME content increased again, to 97.6%. The oxidation stability of the trap grease biodiesel was 0.17 h, and its cold filter plugging point was 4 °C. As the FAME content of the trap grease biodiesel satisfies the Korean Biodiesel Standard, the trap grease biodiesel seems to be applicable for use as an engine fuel after properties improvement.
Keywords: Biodiesel; Trap Grease; Free Fatty Acids; Amberlyst-15; Response Surface Methodology
Performance comparison of batch and continuous flow surface aeration systems by Bimlesh Kumar; Achanta Ramakrishna Rao (1796-1800).
The oxygen transfer rate and the corresponding power requirement to operate the rotor are vital for design and scale-up of surface aerators. The aeration process can be analyzed in two ways such as batch and continuous systems. The process behaviors of batch and continuous flow systems are different from each other. The experimental and numerical results obtained through the batch systems cannot be relied on and applied for the designing of the continuous aeration tank. Based on the experimentation on batch and continuous type systems, the present work compares the performance of both the batch and continuous surface aeration systems in terms of their oxygen transfer capacity and power consumption. A simulation equation developed through experimentation has shown that continuous flow surface aeration systems are taking more energy than the batch systems. It has been found that batch systems are economical and better for the field application but not feasible where large quantity of wastewater is produced.
Keywords: Activated Sludge Process; Continuous Flow; Geometric Similarity; Oxygen Transfer; Power Number; Surface Aerator; Two Film Theory
Experimental and theoretical studies of equilibrium isotherms for pure light hydrocarbons adsorption on 4A zeolite by Muthanna Jabbar Ahmed; Abdul Halim Abdul Karim Mohammed; Abdul Amir Hassan Kadhum (1801-1804).
Experimental and theoretical studies were reported on equilibrium isotherms of pure methane and ethane adsorption on 4A molecular sieve zeolite at 301 K. The experimental equilibria data were measured using the constant-volume method. The Langmuir, the Freundlich, and BET equations were used to fit the pure component experimental data. The results show that both the Langmuir and Freundlich equations correlated the pure component experimental data fairly well with a correlation coefficient of 0.998 and 0.977 for methane and ethane, respectively. The results of this study showed that ethane was more selectively adsorbed than methane on 4A molecular sieve zeolite.
Keywords: Equilibrium Isotherm; Adsorption; 4A Molecular Sieve Zeolite; Methane; Ethane; Light Hydrocarbons
Study of photochemical and sonochemical processes efficiency for degradation of dyes in aqueous solution by Afshin Maleki; Amir Hossein Mahvi; Roya Ebrahimi; Yahya Zandsalimi (1805-1810).
The degradation of two commercially available dyestuffs (C.I. Reactive Black 5 and C.I. Disperse Orange 25) by ultraviolet radiation (UV), ultrasonic irradiation (US), UV/H2O2 and US/H2O2 processes was investigated in a laboratory-scale batch photoreactor equipped with a 55 W immersed-type low-pressure mercury vapor lamp and a sonoreactor with low frequency (42 kHz) plate type transducer at 170 W of acoustic power. The toxicity was also evaluated in acute toxicity studies using Daphnia magna. Results showed that color removal efficiencies by US and US/H2O2 processes were negligible for both dyes. Almost complete disappearance of Reactive Black 5 (97.9%) in UV/H2O2 process was possible after 5 min of irradiation. The maximum color removal efficiency of Disperse Orange 25 after 10 min of irradiation, however, was only 9.2% and reached a maximum value of 41% after 120 min of irradiation. Pseudo-first order kinetics with respect to dyestuffs concentrations was found to fit all the experimental data. The results clearly showed that both dyes examined were toxic to D. magna and resulted in quite low LC50 values.
Keywords: Decolorization; Reactive Black 5; Disperse Orange 25; Advanced Oxidation Processes; Toxicity
Removal of Orange G from aqueous solution by hematite: Isotherm and mass transfer studies by Monoj Kumar Mondal; Sudama Singh; Meka Umareddy; Betty Dasgupta (1811-1815).
The efficiency of hematite for the removal of Orange G from aqueous solution has been studied at various concentrations as a function of time, temperatures and pH. It was found that the low initial concentration, low temperature and low pH favor the removal process. The maximum adsorption of the dye on hematite has been recorded at 25 mg/l concentration, 303 K temperature and pH 3. The negative values of change in free energy and enthalpy indicate the spontaneous and exothermic nature of the process, respectively. Fixation and immobilization of the dye molecules at the surface of hematite as a result of adsorption are responsible for the negative entropy effect. The effect of pH was described by considering coulombic attraction and aqua complex formation approaches. The applicability of various adsorption isotherms—Langmuir, Freundlich and Jossens—was tested in order to find the most suitable isotherm. The Freundlich isotherm was fitted with the data of the present study.
Keywords: Orange G; Hematite; Adsorption Isotherm; Thermodynamic Parameters; Mass Transfer; Aqueous Solution
Variation of bacterial community immobilized in polyethylene glycol carrier during mineralization of xenobiotics analyzed by TGGE technique by Jong Kwang Lee; Woo Jin Lee; Yong-Ju Cho; Doo Hyun Park; Yong-Woo Lee; Jinwook Chung (1816-1821).
Acinetobacter sp. SMIC-1, Cupriavidus sp. SMIC-2, Pseudomonas sp. SMIC-3, Paracoccus sp. SMIC-4, and Pseudomonas sp. SMIC-5 capable of mineralizing xenobiotics (manmade organic compounds) that are diethyleneglycol monomethyleher (DGMME), 1-amino-2-propanol (APOL), 1-methyl-2-pyrrolidinone (NMP), diethyleneglycol monoethylether (DGMEE), tetraethyleneglycol (TEG) and tetrahydrothiophene 1,1-dioxide (Sulfolane) were immobilized mixedly in polyethyleneglycol carrier (SMIC-PEG). TGGE technique was employed to analyze variation of the immobilized bacterial community during xenobiotics being mineralized. The SMIC-PEG mineralized more than 95% of the xenobiotics except sulfolane in 6 days. When activated sludge (AS) was co-immobilized with SMIC community in PEG carrier (AS-SMIC-PEG), degradation efficiency of DGMEE, NPM was a little decreased; however, the degradation of other xenobiotics was neither increased nor decreased significantly. The bacterial community diversity in the SMIC-PEG was gradually decreased in proportion to incubation time in a batch cultivation reactor. SMIC strains in AS-SMIC-PEG were substituted by other bacterial community after 6 days of incubation time in batch cultivation reactor. The SMIC-PEG mineralized around 90% of xenobiotics in a continuous pilot reactor when 100 or 200 mg/L of xenobiotics was fed for 8 hr of hydraulic retention time (HRT); however, the mineralization efficiency was decreased significantly to around 75% when 200 mg/L of xenobiotics was fed for 4 hr of HRT. The mineralization effect of AS-SMIC-PEG for xenobiotics was lower than SMIC-PEG. Bacterial community diversity in both SMIC-PEG and AS-SMIC-EG was decreased in proportion to operation time in the continuous pilot reactor; however, some of them were maintained during operation for more than 50 days.
Keywords: Xenobiotics; PEG Carrier; Ethyleneglycol; Pyrrolidinone; Thiophene; TGGE Technique
A study on air jet drying for water content reduction of sludge by Jung-Eun Lee; Eun-Man Cho (1822-1828).
An air jet drying system composed of a turbo blower, an air ejector and three stage cyclones is constructed to produce a dried powder through water content reduction of dewatered cake obtained from sludge treatment process. The air flow to be ventilated by the turbo blower forms a high speed flow field by passing through the air ejector and a circulative flow field by passing through the cyclones. Dewatered cake, 100 mm in size, is disintegrated by jet and collision through passing the air ejector and becomes fragmented with size no more than 2mm. These fragmented particles follow air flow and are dried as moisture is evaporated from particle surface. A powder composed of 1.6 mm spherical particles is produced from pilot scale equipment of 1 ton/hr under the conditions of air velocity, maximum flow rate and air temperature profile of 84 m/sec, 180 m3/min and 73-28 °C, respectively. The air dried powder with average water content of 49.8 wt% is recovered after drying the dewatered cake with water content of 83.3 wt% in a real operation, indicating 33.5 wt% decrease in water content. It is estimated that the power consumption of the air jet drying system requires 92 kWh/Ton to reduce the water content by 33.5 wt%, which is no more than a half against heat drying system to consume 164 kWh/ton.
Keywords: Air Jet Drying; Sludge; Dewatered Cake; Air Dried Powder; Water Content; Particle Size; Energy Consumption
Improving glutathione extraction from crude yeast extracts by optimizing aqueous two-phase system composition and operation conditions by Xiangting Wu; Linmei Tang; Yinming Du; Zhinan Xu (1829-1835).
PEG-Dextran and PEG-salt aqueous two-phase systems (ATPS) have been applied to separate glutathione (GSH) from crude yeast extracts. Single-factor experiments were carried out to determine the important factors influencing the partition coefficient and extraction yield. The effect of PEG molecular weight, phase-forming components, PEG and Dextran concentration, pH value, and temperature on the GSH partitioning behavior in ATPS was investigated. Three factors, Dextran concentration, pH value, and temperature, were confirmed to have significant influence on the partition coefficient and extraction yield. These factors were further analyzed with the aid of central composite rotatable design and response surface methodology. The optimal conditions for GSH extraction in the PEGDextran system were determined, including PEG molecular weight 6,000, 10% PEG concentration, 14% Dextran concentration, pH 5.2, and temperature 32 °C. A high extraction yield (83.55%) of GSH from crude yeast extracts was achieved under these optimized conditions. This work is very helpful for developing one efficient and cost-effective process for the separation and purification of GSH from yeast broths.
Keywords: Glutathione; Partition; Aqueous Two-phase Systems; Response Surface Analysis
High cell density fermentation of Saccharomyces cerevisiae GS2 for selenium-enriched yeast production by Zheng Wang; Liyang Zhang; Tianwei Tan (1836-1840).
This paper describes a fed-batch fermentation protocol about production of selenium-enriched yeast. Saccharomyces cerevisiae GS2 was selected because of its high tolerance to selenium. The strain GS2 was tested and 122±0.5 g·l −1 dry cell weight was obtained after 30 h cultivation through feed back control of feed rate of glucose according to the concentration of ethanol and dissolved oxygen. Furthermore, the optimal pattern of Na2SeO3 addition was 9 mg Na2SeO3 against 1 g DCW at late exponential phase. With the combination of glucose feeding and Na2SeO3 addition, the final dry cell biomass reached 102±0.4 g·l −1 and a Se uptake level of 2,020±13 mg·Kg−1 was achieved in a 5 l fermentor after 38 h cultivation.
Keywords: High Cell Density Fermentation; Saccharomyces cerevisiae ; Selenium; Yeast
Kinetic model of asymmetric reduction of 3-oxo-3-phenylpropionic acid ethyl ester using Saccharomyces cerevisiae CGMCC No.2266 by Xiaoyan Chen; Zhimin Ou; Guoqing Ying (1841-1846).
The kinetic model of asymmetric reduction of 3-oxo-3-phenylpropionic acid ethyl ester using Saccharomyces cerevisiae CGMCC No.2266 with 10% glucose as co-substrate to realize the regeneration of NADPH was established. The effect factors on reduction, the type and the content of co-substrate and coenzyme, and the changes of the substrate and product content vs. time during the reaction process were investigated. The results indicate that 10% glucose can increase the reaction conversion from 23.0% to 98.4% and NADPH is reducer. The reduction process conforms with sequence mechanisms. The model parameters are as follows: v m =5.0×10−4 mol·L−1·h−1, k1=1.5×10−6 mol·L−1·h−1, k2=3.0×10−3 mol·L−1·h−1. The kinetic model is in good agreement with the experimental data.
Keywords: Saccharomyces cerevisiae CGMCC No. 2266; Biotransformation; 3-Oxo-3-phenylpropionic Acid Ethyl Ester; (S)-3-hydroxy-3-phenylpropionate; Kinetic Model
Screening of Candida utilis and medium optimization for co-production of S-adenosylmethionine and glutathione by Na Shao; Dahui Wang; Gongyuan Wei; Qianpeng Zhang; Xiaoguang Ge; Min Nie (1847-1853).
An effective S-adenosylmethionine and glutathione enriching yeast mutant of Candida utilis CCTCC M 209298 was first screened from plates containing 0.5 g/L of DL-ethionine by complex mutagenesis with UV and γ-ray in this study. Medium components optimization for enhanced co-production of S-adenosylmethionine and glutathione by C. utilis CCTCC M 209298 was further carried out using response surface methodology. The significant factors influencing S-adenosylmethionine and glutathione co-production were selected by Plackett-Burman design as sucrose, KH2PO4 and L-methionine, and Box-Behnken design was applied for further optimization studies. Based on these approaches, the optimized concentrations on medium components for higher co-production of S-adenosylmethionine and glutathione were sucrose 35.4 g/L, (NH4)2SO4 10 g/L, KH2PO4 12.3 g/L, MgSO4·7H2O, 0.05 g/L, CaCl2 0.05 g/L and L-methionine 4.6 g/L. The medium optimization by response surface methodology led to a total production of 589.3 mg/L on S-adenosylmethionine and glutathione, which was 2.4-fold increased compared with the medium without optimization.
Keywords: S-adenosylmethionine; Glutathione; Co-production; Candida utilis ; Medium Optimization
Hydrogen production from wastewater using a microbial electrolysis cell by Yu Hong Jia; Ji Youn Choi; Jae Hun Ryu; Cho Hui Kim; Woo Kyung Lee; Hung Thuan Tran; Rui Hong Zhang; Dae Hee Ahn (1854-1859).
A Microbial electrolysis cell (MEC) was designed to produce a useful and valuable product, hydrogen gas, during the wastewater treatment process. Hydrogen can be produced using the MEC with an applied voltage of over 0.4 V, and the hydrogen yields gradually increased with the increasing of applied voltage. A maximum overall hydrogen efficiency of 21.2% was achieved at an applied voltage of 1.0 V with acetate as substrate, corresponding to a volumetric hydrogen production rate of approximately 0.095 m3 H2/m3 reactor liquid volume/day. A volumetric hydrogen production rate of 0.061 m3 H2/m3 reactor liquid volume/day was achieved when piggery wastewater was fed to the MEC, and the chemical oxygen demand removal rate ranged from 45 to 52%. The results demonstrated that the wastewater, especially an organic-rich item such as piggery wastewater, could be feasibly treated based on this MEC system.
Keywords: Microbial Electrolysis Cell; Hydrogen Production; Organic Removal
Influence of disinfection on bacterial regrowth in pilot distribution system by Young-Cheol Chang; Andrew Andy Randall; OnYou Choi; DuBok Choi; Hoon Cho; Shintaro Kikuchi (1860-1863).
A correlation between heterotrophic plate count (HPC) and chloramine residual in pilot distribution systems (PDSs) was investigated. The data was derived from an AWWARF (the Awwa Research Foundation) and Tampa Bay Water tailored collaboration project to determine the effect of blending different waters on distribution system water quality. Seven different finished waters were produced from surface, ground, or simulated brackish water sources on site and fed to 18 independent PDSs, either as a single finished water or as a blend of several finished waters. Significantly higher numbers for PDS HPC were observed below 0.06 mg/L of combined chlorine residual. Changes in assimilable organic carbon (AOC) levels between influent and effluent of the PDSs increased as disinfectant dosage decreased in distribution systems. Significant differences between input and output AOC (ΔAOC) were observed when the chloramine residual was less than 1.0 mg/L, and particularly when less than 0.5 mg/L. High HPC counts often occurred when chloramine residual was less than 0.5 mg/L, regardless of AOC levels or AOC stability. However AOC instability could occur at high influent AOC levels even in the presence of residual greater than 0.5 mg/L, with corresponding high HPC counts.
Keywords: Assimilable Organic Carbon; Biostability; Chloramine; Pilot Distribution System
Hybrid neural network for prediction of CO2 solubility in monoethanolamine and diethanolamine solutions by Mohd Azlan Hussain; Mohamed Kheireddine Aroua; Chun-Yang Yin; Ramzalina Abd Rahman; Noor Asriah Ramli (1864-1867).
The solubility of CO2 in single monoethanolamine (MEA) and diethanolamine (DEA) solutions was predicted by a model developed based on the Kent-Eisenberg model in combination with a neural network. The combination forms a hybrid neural network (HNN) model. Activation functions used in this work were purelin, logsig and tansig. After training, testing and validation utilizing different numbers of hidden nodes, it was found that a neural network with a 3-15-1 configuration provided the best model to predict the deviation value of the loading input. The accuracy of data predicted by the HNN model was determined over a wide range of temperatures (0 to 120 °C), equilibrium CO2 partial pressures (0.01 to 6,895 kPa) and solution concentrations (0.5 to 5.0M). The HNN model could be used to accurately predict CO2 solubility in alkanolamine solutions since the predicted CO2 loading values from the model were in good agreement with experimental data.
Keywords: Diethanolamine; Monoethanolamine; CO2 Solubility; Kent-Eisenberg Model; Hybrid Neural Network
Chemical absorption of carbon dioxide into phenyl glycidyl ether solution containing THA-CP-MS41 catalyst by Young-Son Choe; Kwang-Joong Oh; Min-Chul Kim; Sang-Wook Park (1868-1875).
Carbon dioxide was absorbed into the phenyl glycidyl ether (PGE) solution within a range of 0–2.0 kmol/m3 in a stirred batch tank with a planar gas-liquid interface at 333–363 K and 101.3 kPa. Trihexylamine-immobilized on chloropropyl-functionalized MCM-41 (THA-CP-MS41) was used as a mesoporous catalyst, dispersed in organic liquid for the reaction between carbon dioxide and PGE. The measured absorption rates were analyzed to obtain the reaction kinetics of the consecutive chemical reactions which consisted of two steps using the mass transfer mechanism based on film theory. The overall reaction kinetics, analyzed with the pseudo-first-order reaction constant in the consecutive reaction model, was equivalent to the consecutive reaction kinetics. Effects of polar solvent, such as N, N-dimethylacetamide, N-methyl-2-pyrrolidinone, and dimethyl sulfoxide, on the reaction rate constants were observed using the solubility parameter of the solvent.
Keywords: Absorption; Carbon Dioxide; Phenyl Glycidyl Ether; Trihexylamine; MCM-41
The effect of ethane on the performance of commercial polyphenylene oxide and Cardo-type polyimide hollow fiber membranes in CO2/CH4 separation applications by Mahdi Pourafshari Chenar; Houman Savoji; Mohammad Soltanieh; Takeshi Matsuura; Shahram Tabe (1876-1881).
Impurities such as hydrogen sulfide, water vapor and heavy hydrocarbons in natural gas have considerable effects on the membrane performance. Small amounts of condensable and polymer soluble components in the feed gas cause swelling or plasticization of glassy membranes, leading to a reduction in membrane selectivity. In the present research the influence of ethane was investigated on the permeance and selectivity of two commercially available hollow fiber membranes, namely Cardo-type polyimide and PPO hollow fibers for CO2/CH4 separations. It was concluded that the gas mixture permeation rate was increased in the presence of C2H6. However, the CO2/CH4 separation factors remained almost the same in the presence and absence of the C2H6.
Keywords: Membrane Gas Separation; Natural Gas; Gas Sweetening; Ethane; Hollow Fiber
Removal of NO using surface modified activated carbon fiber (ACF) by impregnation and heat-treatment of propellant waste by Keun Sig Yoon; Seung Kon Ryu (1882-1886).
The surface of activated carbon fiber was modified by impregnation and heat-treatment of propellant waste to introduce nitrogen functional groups such as pyridines, pyridones and pyrrols. The pore structure and specific surface area of those modified ACFs were slightly changed; however, the NO removal capacity of the surface modified ACF by propellant waste increased about twice that of the as-received ACF due to the addition of chemical adsorption by nitrogen functional groups. Propellant waste can be used as an ACF surface modifier for the removal of NOx.
Keywords: Activated Carbon Fiber; Surface Treatment; Propellant; Adsorption; NO Removal
High pressure isothermal vapor-liquid equilibria for the binary system of carbon dioxide (CO2)+1,1,1-trifluoroethane (R-143a) by Seol A. Kim; Ki-Pung Yoo; Jong Sung Lim (1887-1891).
Isothermal vapor-liquid equilibrium data for the binary mixture of carbon dioxide (CO2)+1,1,1-trifluoroethane (HFC-143a) were measured within the temperature range of 273.15–333.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The experimental data were correlated with the Peng-Robinson equation of state (PR-EOS) using the Wong-Sandler mixing rules combined with the NRTL excess Gibbs free energy model. The values calculated by the PR EOS with the W-S mixing rules show good agreement with our experimental data.
Keywords: Carbon Dioxide (CO2); HFC-143a; Vapor-liquid Equilibria (VLE); Peng-Robinson Equation of State (PR EOS)
Optimization of single-walled carbon nanotube growth and study of the hysteresis of random network carbon nanotube thin film transistors by Seung Hyun Hur (1892-1896).
Random network single-walled carbon nanotube (SWNT)-based thin film transistors show excellent properties in sensors, electronic circuits, and flexible devices. However, they exhibit a significant amount of hysteresis behavior, which should be solved prior to use in industrial applications. This paper provides optimum conditions for the growth of random network SWNTs and reveals that the observed hysteresis behavior originates from the charge exchange between the SWNTs and the dielectric layer rather than from changes in the intrinsic properties of the SWNTs. This was proven by studying the conditions of stepwise gate sweep experiments and time measurements. This paper also shows that top gate SWNT thin film transistors (TFTs) with an SU-8 dielectric layer could provide a practical solution to the hysteresis problem for SWNT TFTs in electronic circuit applications.
Keywords: Single Walled Carbon Nanotubes; Thin Film Transistor; Hysteresis; Catalyst
Fast preparation of citrate-stabilized silver nanoplates and its nanotoxicity by Jinkyu Roh; Eun-Jung Park; Kwangsik Park; Jongheop Yi; Younghun Kim (1897-1900).
Citrate-stabilized silver nanoplates (AgNPs) were prepared via a seed-mediated method without surfactants, such as cetyltrimethylammonium bromide (CTAB), in a short amount of time (15 min). Silver seeds with 3–4 nm in diameter were added to a growth solution containing AgNO3, trisodium citrate (TSC) and L-ascorbic acid (AA). The size of the AgNPs depended on the concentration of the silver seed and TSC. The physical properties of the AgNPs were analyzed by transmission electron microscopy (TEM) and by an ultraviolet-visible (UV-vis) spectrophotometer. In addition, we tested the nanotoxicity of AgNPs prepared in TSC solution to the spleen of a rat, and found that AgNPs induced inflammation and white spots on the surface of the spleen.
Keywords: Silver Nanoparticles; Nanoplates; Citrate; Nanotoxicity
Preparation of high purity nano silica particles from blast-furnace slag by Sun-Jae Kim; Seong-Gyu Seo; Sang-Chul Jung (1901-1905).
High purity nano silica was synthesized using acid treatment and surface modification from blast-furnace slag generated in the steel industry. Blast-furnace slag was treated with nitric acid to extract high-purity insoluble silica. Nano silica was then produced using filtration and surface modified by cation surfactant-Cetyltrimethyl Ammonium Bromide (CTAB). The Zeta potential of silica was tested under various alkaline conditions. Synthesized silica remained electronegative throughout the pH range tested and the number of hydroxyl groups existing on the silica surface was highest when the pH was 9. The size of silica particles was smallest when the modification temperature was 60 °C. The average size of silica particles modified with 3 wt% CTAB was 107.89 nm, while the average size of unmodified silica was 240.38 nm. After extracting silica, pH of the remaining solution was adjusted by adding CaO and then highpurity calcium nitrate crystals were extracted using solubility difference. It was found experimentally that enriching the solution to a high specific gravity (1.63–1.65) before crystallization is preferable for efficient calcium nitrate recovery.
Keywords: Nano Silica; Slag; Surface Modification; Zeta Potential; Particle Size
Stability-enhanced solid dispersion formulation of amorphous raloxifene hydrochloride by Chin Sung Cho; Taek Hwan Shin; Jong Lae Lim; Ki Young Moon; Duk Ki Kim; Young Wook Choi (1906-1909).
To develop a stabilized formulation of amorphous raloxifene hydrochloride (RXF), solid dispersion granules (SDG) of amorphous RXF were prepared by fluidized bed granulation with non-pareil beads, compressed and filmcoated to produce solid dispersion tablets (SDT). Polymorphic changes in RXF were inhibited by SDG formulation. Drug content, impurity, and dissolution profile of SDT revealed that the SDT meets the acceptance criteria, and the content of RXF was maintained over 95% for 5 months at accelerated conditions of 40 °C and 75% R.H. In comparative dissolution study of reference tablet (Evista®) and SDT, the similarity factor (f2) provided evidence for similar dissolution profiles between two formulations. Therefore, we suggest the usefulness of SDT for the development of generic pharmaceuticals containing amorphous RXF.
Keywords: Raloxifene; Polymorphs; Solid Dispersion; Stability; Dissolution
Adsorption of carbon dioxide using polyethyleneimine modified silica gel by Tao Zhu; Seil Yang; Dae Ki Choi; Kyung Ho Row (1910-1915).
To find an ideal adsorbent for carbon dioxide capture, a new polyethyleneimine modified silica gel material was synthesized with a simple procedure. Three silica gel materials with various particle sizes (15, 25 and 40–63 μm) were prepared and functionalized with polyethyleneimine. The carbon dioxide adsorption amounts of modified silica gel and non-modified silica gel were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influence of gas pressure and particle size on adsorption was discussed. Experimental data showed that the carbon dioxide adsorption capacity of modified silica gel was better than non-modified silica gel, and the adsorption capacity gradually decreased with increasing particle size. The smaller particle size (15 μm) PEI modified silica gel had the largest adsorption capacity, at 298.15 K, and the adsorption amounts of various particle sizes of PEI-silica better fit the Langmuir isotherm model.
Keywords: Adsorption; Adsorbent; Silica Gel; Carbon Dioxide; PEI
Effects of exposure wavelength and surface preparation conditions on the generation of blister defects in organic insulator layer by Moonchul Cho; Yeong-Beom Lee (1916-1921).
We report a new factor for blister formation on organic photoresist (PR) and an improvement of this process. We have studied blister formation from more different standpoints, such as processes and instrumentation, than did previous reports. Unexpectedly, we observed radical blister formation in an experiment that involved exposure without any ultraviolet (UV) filters. After a series of experiments, the data showed that the organic PR blister problem was most likely caused by the specific wavelength of the UV light field on exposure. Surface preparations using wet and dry treatments prior to coating a thin film of organic PR on silicon nitride (SiNx) glass wafer were studied. By comparing exposure to different spectra, both with and without a UV filter, we confirmed the key point of blister formation in case of the organic PR. Additionally, various treatments of SiNx prior to the coating of organic PR were primarily performed to improve organic PR adhesion to SiNx glass substrate.
Keywords: Blister; Adhesion; Organic Photoresist; Silicon Nitride; TFT Process
Adsorption and column flotation studies on talc using anionic and cationic collectors by Hulya Kursun; Ayten Ates (1922-1927).
Adsorption properties and column flotation were studied to investigate the interaction of the anionic and cationic collectors and flotation recoveries for talc mineral. Adsorption capacity is dependent on pH, adsorption time, temperature, collector concentration, and particle size. Langmuir adsorption model was suitable for describing isotherms. Analyses were carried out using UV spectrometry. In this study, we analyzed some parameters affecting column flotation performance. It was determined that adsorption capacity, especially, had an important role in column flotation enrichment.
Keywords: Adsorption; Column Flotation; Talc; Langmuir