Korean Journal of Chemical Engineering (v.29, #3)

Carbon nanotube yarns by Junbeom Park; Kun-Hong Lee (277-287).
A CNT yarn is a collection of interlocked CNTs which form a long and continuous fiber of macroscopic scale. CNT yarns of more than a kilometer are now available so that they have been drawing ever-growing attention from the scientific community. In principle, CNT yarns can inherit the excellent electrical, mechanical and chemical properties of CNTs provided they are produced perfectly. In this perspective review, the production methods of CNT yarns are extensively investigated and reported in detail. Although CNT yarns have a great potential to revolutionize our future, it can only be possible by improving their essential material properties such as tensile strength and edectrical conductivity.
Keywords: Carbon Nanotube; Fiber; Yarn

Clean and facile synthesis of triuret from urea and dimethyl carbonate (DMC) under mild conditions by Jianchao Chen; Peihua Zhao; Yaqing Liu; Hua Liu; Futian Zhu (288-290).
Triuret has been successfully synthesized by the reaction of urea with dimethyl carbonate (DMC) under mild conditions in the presence of potassium methoxide as a catalyst. It has been fully characterized by FT-IR, 1H-NMR, 13C-NMR, and MS. Effects of the catalyst, the molar ratio of starting materials, and the reaction time on the obtained product were examined in detail. It was found that when n (urea): n (DMC)=1.2: 1, 6 h, and 0.8% catalyst, the yield of triuret can reach 98.1%. Especially, this novel procedure is reported for the first time and has many significant advantages such as easy and clean synthesis, simple work up, and high yields.
Keywords: Triuret; Dimethyl Carbonate; Urea; Clean Synthesis

A systematic model calibration methodology based on multiple errors minimization method for the optimal parameter estimation of ASM1 by JungJin Lim; MinHan Kim; MinJung Kim; TaeSuk Oh; OnYu Kang; Booki Min; Ambati Seshagiri Rao; ChangKyoo Yoo (291-303).
A one-step model calibration methodology of the activated sludge model no. 1 (ASM1) of a full-scale wastewater treatment plant (WWTP) is proposed. First, the key parameters among all parameters of the ASM1 model are selected by sensitivity analysis based on the effluent quality index. Second, multiple response surface methodology (MRSM) is conducted to find the optimal parameter values of the ASM1 model. Lastly, an MRSM analysis is conducted in order to determine the optimal parameter values. This study was conducted in order to develop a new systematic model calibration methodology that can greatly help the modeler to find the optimal solution by selecting the key parameters and optimizing the parameters. In two case studies of simple activated sludge process and a full-scale plant, the experimental results indicated that the calibrated models can improve the prediction quality of the ASM model and the efficiency of the modeling.
Keywords: Activated Sludge Model; Multiple Error Minimization; Sensitivity Analysis; Response Surface Methodology; Multiple Response Surface Methodology

Intrinsic kinetics of the Fischer-Tropsch synthesis over an impregnated cobalt-potassium catalyst by Hossein Atashi; Mohsen Mansouri; Seyyed Hossein Hosseini; Mohammad Khorram; Ali Akbar Mirzaei; Masoud Karimi; Ghobad Mansouri (304-309).
The optimal amount of 15 wt%Co/10 wt%K/Al2O3 catalyst was prepared using the impregnation technique in order to study the kinetics of the Fischer-Tropsch synthesis. The rate of synthesis was measured in a fixed-bed micro reactor with H2/CO feed ratio of 1–3 and space velocity in the range of 2,700–5,200 h−1 under reactor pressure of 8 bar and a temperature range of 210–240 °C. The experimental data were best fitted by a Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach rate in the form of $ - r_{CO} = (k_2 K_1 P_{CO} P_{H_2 } )/(1 + K_1 P_{CO} )$ . Furthermore, the data were fitted fairly well by a power law equation in the form of $ - r_{CO} = kP_{CO}^{1.32} P_{H_2 }^{1.42} $ . The activation energies for LHHW approach model and power law equation were obtained as 138.5 kJ/mol and 87.39 kJ/mol, respectively.
Keywords: Fischer-Tropsch Synthesis; Co/K/Al2O3 Catalyst; Fixed-bed Reactor; Kinetic Modeling; Impregnation Technique

CoMoS/Al2O3 catalyst, which was prepared using Co(MeAA)2·2H2O as a new Co precursor, showed activity for hydrodesulfurization (HDS) higher than that of conventional catalysts, which were prepared using Co(NO3)·6H2O as a Co precursor and/or by adding ethylene-di-amine-tetra-acetic acid (EDTA) as a chelating agent. Catalyst of a similar activity was also obtained simply by impregnating a conventional CoMo/Al2O3 catalyst with an aqueous solution of methylacetoacetate (MeAA) followed by drying and sulfidation. The added MeAA reacted with Co to produce Co(MeAA)2·2H2O on the catalyst surface during impregnation step, such that the resulting catalyst became similar to one prepared by direct impregnation with Co(MeAA)2·2H2O. The in-situ synthesis of Co(MeAA)2·2H2O on the catalyst surface was advantageous over the method of directly adding the Co precursor to the impregnation solution because the former method did not use a basic material, which was required for the synthesis of the Co precursor. Furthermore, MeAA was soluble in water, whereas Co(MeAA)2·2H2O had to be dissolved in an organic solvent, e.g., 1,4-dioxane. The Co species in the MeAA-added catalysts were sulfided at temperatures higher than those of conventional catalysts, and consequently the former catalysts contained greater amounts of the HDS-active CoMoS phase than the latter.
Keywords: Hydrodesulfurization; CoMoS; Methylacetoacetate; Chelating Agent

Ce X Zr1−X O2 catalysts with different cerium content (X) (X=0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0) were prepared by a sol-gel method. Among these catalysts, Ce0.6Zr0.4O2 showed the best catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. To see the effect of acidity and basicity of transition metal oxide/Ce0.6Zr0.4O2 catalysts on the catalytic performance in the direct synthesis of dimethyl carbonate, MO/Ce0.6Zr0.4O2 (MO=Ga2O3, La2O3, Ni2O3, Fe2O3, Y2O3, Co3O4, and Al2O3) catalysts were prepared by an incipient wetness impregnation method. NH3-TPD and CO2-TPD experiments were carried out to measure acidity and basicity of the supported catalysts, respectively. Experimental results revealed that both acidity and basicity of the catalysts played a key role in determining the catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. The amount of dimethyl carbonate produced over MO/Ce0.6Zr0.4O2 catalysts increased with increasing both acidity and basicity of the catalysts. Among the catalysts tested, Ga2O3/Ce0.6Zr0.4O2, which had the largest acidity and basicity, exhibited the best catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide.
Keywords: Dimethyl Carbonate; Methanol; Carbon Dioxide; Acid-base Property; Ceria-zirconia; Supported Transition Metal Oxide

Coumarin and 7-hydroxycoumarin (7HC) were photo-dimerized in an aqueous solution of polymeric β-cyclodextrin (PβCD) to investigate the effect of the photo-dimerization on the viscosity of PβCD solution. PβCD was prepared by cross-linking β-cyclodextrin (βCD) using epichlorohydrin. The content of βCD residues in PβCD, determined by a colorimetric method using phenolphthalein as an indicator, was 28.8 wt%. The solubility of coumarin increased with increasing concentration of PβCD, because the benzene ring of coumarin was included in the hydrophobic cavity of βCD residue. PβCD also increased the solubility of 7HC, but the solubilizing effect on 7HC was much less than that on coumarin, possibly because the hydroxy group on the benzene ring was likely to suppress the inclusion in the cavity of βCD. And, the photo-dimerization degree of 7HC in an aqueous solution of PβCD was about half than that of coumarin, possibly because the vinyl ether of pyrone group of 7HC could be concealed in the cavity of βCD. The photo-dimerization of coumarin in an aqueous solution of PβCD could significantly increase the viscosity of the solution. One coumarin dimer would hydrophobically interact with two βCD residues so it can act as a cross-linker for PβCD.
Keywords: Coumarin; Polymeric β-Cyclodextrin; Photo-dimerization; Viscosity

Krill oil including astaxanthin was extracted using supercritical CO2 and hexane. The effects of different parameters such as pressure (15 to 25MPa), temperature (35 to 45 °C), and extraction time, were investigated. The flow rate of CO2 (22 gmin−1) was constant for the entire extraction period of 2.5 h. The maximum oil yield was found at higher extraction temperature and pressure. The oil obtained by SC-CO2 extraction contained a high percentage of polyunsaturated fatty acids, especially EPA and DHA. The acidity and peroxide value of krill oil obtained by SC-CO2 extraction were lower than that of the oil obtained by hexane. The SC-CO2 extracted oil showed more stability than the oil obtained by hexane extraction. The amount of astaxanthin in krill oil was determined by HPLC and compared at different extraction conditions. The maximum yield of astaxanthin was found in krill oil extracted at 25 MPa and 45 °C.
Keywords: Krill; Oil; Astaxanthin; Supercritical Carbon Dioxide Extraction; Hexane

Solvent effects on gravure-printed organic layers of nanoscale thickness for organic solar cells by Jiyeon Lee; Aran Kim; Sung Min Cho; Heeyeop Chae (337-340).
The effects of different solvents on the fabrication of organic photovoltaic cells by gravure printing are reported. Polymer bulk heterojunction solar cells were fabricated with ITO/PEDOT: PSS/P3HT: PCBM/Al layer structures using 4–9 wt% mixtures of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) in 1,2-dichlorobenzene to optimize solution viscosity for gravure printing. 7 wt% P3HT: PCBM showed optimal efficiency of 1.64% and resulted in an active layer 340 nm thick. Three solvents, 1,2-dichlorobenzene, chloroform, and chlorobenzene, were tested and a 1: 1 ratio mixture of 1,2-dichlorobenzene and chloroform resulted in the best efficiency of 2.21%. This study demonstrates the importance of solvent effects in the gravure printing of organic photovoltaic devices.
Keywords: Organic Solar Cells; Gravure Printing; Solvent Effects

This research investigated optimal energy utilization with pinch technology based on an actual gelatin production factory using a three-effect evaporator (TEE). A TEE is a well-known device used extensively when concentrating process fluid with large amounts of boiler steam. Under ideal energy use conditions, the exhaust heat can be recovered with the addition of a heat pump system. The study results showed that the original energy demand and discharge of the TEE were 1,736.2 and 1,733.2 kWh, respectively. Simulating the pinch technology use, the energy demand and discharge decreased to 1,531.5 and 1,527.7 kWh, respectively. When the heat pump was used to recover the exhaust heat, 324 kL per annum of fuel oil was saved, while electricity use increased 131 kWh. The total investment cost was 86,550 US$, but the total annual operation cost could save up to 166,421 US$. The net present value was estimated to be 544,316 US$ with a 5-year equipment operation. The investment expense could be completely recovered within a seven-month remuneration period.
Keywords: Vaporized Concentration; Pinch Technology; Heat Pump; Three-effect Evaporator

Composite cathodes with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and Ce0.9Gd0.1O1.95 (GDC) are investigated to assess for solid oxide fuel cell (SOFC) applications at relatively low operating temperatures (650–800 °C). LSCF with a high surface area of 55 m2g−1 is synthesized via a complex method involving inorganic nano-dispersants. The fuel cell performances of anode-supported SOFCs are characterized as a function of compositions of GDC with a surface area of 5 m2g−1. The SOFCs consist of the following: LSCF-GDC composites as a cathode, GDC as an interlayer, yttrium stabilized zirconia (YSZ) as an electrolyte, Ni-YSZ (50: 50 wt%) as an anode functional layer, and Ni-YSZ (50: 50 wt%) for support. The cathodes are prepared for 6LSCF-4GDC (60: 40 wt%), 5LSCF-5GDC (50: 50 wt%), and 4LSCF-6GDC (40: 60 wt%). The 5LSCF-5GDC cathode shows 1.29 Wcm−2, 0.97 Wcm−2, and 0.47 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. The 6LSCF-4GDC shows 0.92 Wcm−2, 0.71 Wcm−2, and 0.54 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. At 780 °C, the highest fuel cell performance is achieved by the 5LSCF-5GDC, while at 680 °C the 6LSCF-4GDC shows the highest performance. The best composition of the porous composite cathodes with LSCF (55 m2g−1) and GDC (5 m2g−1) needs to be considered with a function of temperature.
Keywords: Solid Oxide Fuel Cell; Mixed Conductor; Nano Dispersant; Anode Supported Cell; Composite Cathode

A TiO2 blocking layer in DSSC provides good adhesion between the fluorinated tin oxide (FTO) and an active TiO2 layer, and represses the electron back transport between electrolyte and FTO by blocking direct contact. In addition, it offers a more uniform layer than bare FTO glass. In this study, a dense TiO2 layer is prepared by electrodeposition technique onto an FTO substrate, and it is further used for efficiency measurement of dye-sensitized solar cell (DSSC). The thickness of TiO2 blocking layers is controlled by applied voltage and deposition time. The morphology and crystalline structure of TiO2 blocking layers are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The effect of thickness of TiO2 blocking layers on transmittance is also examined by UV-vis spectrophotometer. For the best performance of the cell efficiency, the optimum blocking layer thickness is about 450 nm fabricated at 0.7 V for 20 min. The conversion efficiency from the DSSC including the optimum blocking layer is 59.34% improved compared to the reference cell from 2.41% to 3.84%. It demonstrates that the electrodeposition is a useful method to produce TiO2 blocking layer for DSSC applications.
Keywords: DSSC; Blocking Layer; Electrodeposition; TiO2 Film

Effect of addition of weak acids on CO2 desorption from rich amine solvents by Min Du; Bo Feng; Hui An; Wenqiang Liu; Li Zhang (362-368).
Experiments were conducted to study the effect of addition of four weak acids (adipic, suberic, phthalic and sebacic acids) on the regeneration of three types of CO2-loaded rich solvents (Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA)). It was found that CO2 could be released faster and in a larger quantity when the amount of acid added to the solvent was increased while other desorption conditions were maintained unchanged. Adipic acid appeared to be more effective than phthalic, suberic and sebacic acids in enhancing solvent regeneration rate. Among the three amines investigated, MEA had the highest CO2 desorption rate, while DEA saved the most energy. The effect of adipic acid residue in the MEA solvent on CO2 absorption was also investigated. The residue acid reduced the absorption capacity of the MEA solvent significantly when the solvent concentration was low and slightly when the concentration was high.
Keywords: CO2 Absorption; pH Swing; Solvent; CO2 Desorption

Effect of hydraulic retention time and temperature on submerged membrane bioreactor (SMBR) performance by Alireza Hemmati; Mohsen Maghami Dolatabad; Fereshteh Naeimpoor; Afshin Pak; Toraj Mohammdi (369-376).
Water shortages and strict environmental provisions necessitate wastewater renovation using various wastewater treatment methods, among which applications of submerged membrane bioreactors (SMBRs) are rapidly increasing due to their advantages such as high loading capacity and quality of effluent. In this work, the effect of hydraulic retention time (HRT 8, 10 and 12 h) and temperature (25, 30 and 35°C) on membrane fouling and sludge production was investigated in a 5-Liter SMBR equipped with immersed PVDF hollow fiber membrane module. Phenolic synthetic wastewater and acclimatized activated sludge with phenol during a 2-month period were used as toxic and microbial sources, respectively. Results showed that by increasing HRT membrane fouling decreases, while excellent treatment performance of over 99.5% phenol and 95% COD removals was achieved at all HRTs. Therefore, HRT=8 h corresponding to the highest effluent flow rate of 12 L/m2·h was used to investigate the effect of temperature, resulting in phenol and COD removals of higher than 99 and 96%, respectively, at all temperatures. Membrane fouling occurred at 12, 5 and 3 days for 25, 30 and 35 °C, respectively. Additionally, the effect of HRT and temperature on mixed liquor volatile suspended solid (MLVSS) as a measure of biomass was examined. MLVSS concentration showed decreases with increasing HRT and temperature. Overall, it was shown that SMBR can be used to efficiently treat phenolic wastewater at a range of flow rates and temperatures, among which HRT=8 h and T=25 °C are the preferred operating conditions, resulting in high flow rate and low membrane fouling.
Keywords: Submerged Membrane Bioreactor (SMBR); Hollow Fiber Membrane; Hydraulic Retention Time; Temperature; Membrane Fouling

Photocatalytic degradation of benzene, toluene, ethylbenzene, and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth by Laksana Laokiat; Pongtanawat Khemthong; Nurak Grisdanurak; Paiboon Sreearunothai; Wanwisa Pattanasiriwisawa; Wantana Klysubun (377-383).
Transition metal (Fe, V and W)-doped TiO2 was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO2 (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO2. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO2 lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO2 were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.
Keywords: Photocatalytic Degradation; BTEX; Transition Metal-doped TiO2

The concentration of four mineral salts in the medium for the production of carboxymethylcellulase (CMCase) by Psychrobacter aquimaris LBH-10 were optimized using orthogonal array method (OAM) and response surface method (RSM) and their results from two statistical methods were compared. The analysis of variance (ANOVA) of data from central composite design (CCD) based on OAM indicated that potassium phosphate gave the highest percentage participation for cell growth as well as production of CMCase. However, their relative participations of four salts for cell growth were different from those for production of CMCase. The ANOVA of results from RSM indicated that highly significant factors (“probe>F” less than 0.0001) for cell growth were K2HPO4 and (NH4)2SO4, whereas those for production of CMCase were K2HPO4, NaCl, and MgSO4·7H2O. The optimal concentration of K2HPO4, NaCl, MgSO4·7H2O, and (NH4)2SO4 for cell growth extracted by Design Expert Software based on RSM were 7.10, 0.84, 0.24, and 0.33 g/L, respectively, whereas those for production of CMCase were 3.00, 0.52, 0.34, and 0.45 g/L. The optimal concentrations of salts for cell growth and production of CMCase using RSM basically coincided with those using OAM as well as those from ‘one-factor-at-a-time’ method. The production of CMCase by P. aquimaris LBH-10 with optimized concentrations of salts was 273.0 U/mL, which was enhanced by 1.27 times higher than the previous report.
Keywords: Psychrobacter aquimaris ; Carboxymethylcellulase; Optimization; Salts; Orthogonal Array Method; Response Surface Method

Mathematical analysis of colonial formation of embryonic stem cells in microfluidic system by Seul Ki Min; Byung Man Lee; Jin Ha Hwang; Sung Ho Ha; Hwa Sung Shin (392-395).
A fluidic environment affects mechanochemical characteristics of embryonic stem cells (ESCs). Perfusion is recognized as an attractive culture mode of ESCs since the steady fluidic state can enhance ESCs’ controllability, supporting a unique cell culture condition. Cellular membrane motility presents important information about cellular dynamics such as adhesion, spreading, and migration. Thus, an investigation of the perfusion-induced membrane motility is significant to understand the mechanochemical behavior of ESCs in the steady culture state. In this research, we suggest L fr , the ratio of circumferential membrane unattached to other cells’ to the cell’s circumference, as a new parameter to characterize cells’ shape and motility. L fr of embryonic stem cells has positive correlations with cellular area (A r ) and free peripheral length (L f ) but a negative correlation with roundness (R n ). We also propose a mathematical model representing ESCs’ membrane motilities and demonstrate their colonical behavior.
Keywords: Embryonic Stem Cells; Morphology; Self-renewal; Perfusion Culture; Free Peripheral Length Ratio (L fr )

Sinigrin is a major glucosinolate present in Indian mustard (Brassica juncea L.) seeds as the precursor of the anticancer compound allyl isothiocyanate. In the present study, the adsorption and desorption characteristics of six macroporous ion-exchange resins for the separation of sinigrin from crude aqueous extracts have been compared. The results indicated that D261 resin showed the best adsorption and desorption capacity to sinigrin, and its adsorption data fit best to the Freundlich isotherm. The dynamic adsorption/desorption experiments were carried out to optimize the separation process. After treatment with D261 resin in one run, the purity of sinigrin in the product was increased 15.57-fold from 3.75% to 58.37% with the recovery of 79.82%. Meanwhile, the separation effect of D261 resin was also supported by UV and IR. The separation process using macroporous ion-exchange resin in our paper provides a novel, rapid and economical method for separation of sinigrin.
Keywords: Sinigrin; Indian Mustard; Brassica juncea L.; Macroporous Ion-exchange resin; Separation

Thequasi-chemical nonrandom lattice fluid model is capable of describing thermodynamic properties for complex systems containing associating fluids, polymer, biomolecules and surfactants, but this model fails to reproduce the singular behavior of fluids in the critical region. In this research, we used the quasi-chemical nonrandom lattice fluid model and combined this model with a crossover theory to obtain a crossover quasi-chemical nonrandom lattice fluid model which incorporated the critical scaling laws valid asymptotically close to the critical point and reduced to the original quasi-chemical nonrandom model far from the critical point. The crossover quasi-chemical nonrandom lattice fluid model showed a great improvement in prediction of the volumetric properties and second-order derivative properties near the critical region.
Keywords: Crossover; Quasi-chemical; Lattice Model; Critical Region; Second-order; Derivative Properties

Pressure-composition isotherm is obtained for the carbon dioxide+2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) using static apparatus with a variable volume view cell at temperature range from 40 °C to 120 °C and pressure up to 130 bar. This system exhibits type-I phase behavior with a continuous mixture-critical curve. The experimental result for carbon dioxide+PFPMA mixture was modeled using the Peng-Robinson (P-R) and multi-fluid nonrandom lattice fluid (MF-NLF) equation of state. Experimental cloud-point data of pressure up 470 bar and temperature to 182 °C were reported for the binary mixture of poly(2,2,3,3,3-pentafluoropropyl methacrylate) [Poly(PFPMA)] in supercritical carbon dioxide and dimethyl ether (DME). The Poly(PFPMA)+carbon dioxide and Poly(PFPMA)+DME systems showed LCST behavior.
Keywords: High Pressure Phase Behavior; Carbon Dioxide; Dimethyl Ether; Poly(2,2,3,3,3-Pentafluoropropyl Methacrylate); 2,2,3,3,3-Pentafluoropropyl Methacrylate; Peng-Robinson Equation of State; MF-NLF Equation of State