Korean Journal of Chemical Engineering (v.28, #7)

Key technological elements in dye-sensitized solar cells (DSC) by Shi-Woo Rhee; Woosung Kwon (1481-1494).
The best cell efficiency of lab scale dye sensitized solar cell (DSC) exceeds 11%, but there are still many technological problems to overcome for commercialization. This review describes key technological elements in DSC, including working electrodes with dye/TiO2/electrolyte interfaces, quasi solid state electrolyte with ion diffusion, and counter electrodes with electrolyte-catalytic electrode interfaces. Their operating principles, equivalent electric circuits and measurement techniques are described.
Keywords: Dye-sensitized Solar Cells; TiO2-dye Junctions; Electrolytes; Counter Electrodes; Electrochemical Impedance Spectroscopy

Modeling and simulation of hollow fiber CO2 separation modules by Hyun Ju Jung; Sang Hoon Han; Young Moo Lee; Yeong-Koo Yeo (1497-1504).
We developed two models for the CO2 separation process by hollow-fiber membrane modules. The explicit model, which is based on mass balances for the separation modules, is compared with the multilayer perceptrons (MLP) back-propagation neural networks model. Experimental data obtained from single-stage module with recycle are used to validate the explicit model as well as to train the MLP neural model. The effectiveness of the model is demonstrated by little discrepancy between experimental data and computational results. The explicit model for the single-stage module can easily be extended to the multi(three)-stage module. Because of the lack of experimental data for multi-stage modules, computational data from the explicit model with and without recycle are used as training data set for the MLP neural model. We examined the effects of recycle on the recovery based on the results of numerical simulations, and could see that the predicting performance is improved by recycle for multi-stage module. From the results of numerical simulations, the proposed models can be effectively used in the analysis and operation of gas separation processes by hollow-fiber membrane modules.
Keywords: Multi-stage Module; Multilayer Perceptrons Back-propagation Networks; Modeling of Separation Process; Carbon Dioxide; Hollow Fiber Membrane

A new forecasting method for system marginal prices based on power supply and demand by Kee Jun Lee; Tae Hwan Lee; Lae-Hyun Kim; Yeong Koo Yeo (1505-1510).
A new forecasting scheme is presented of short-term system marginal price (SMP) using past data on power supply and demand as well as past cost data. The forecasting of SMP is one of the most significant factors in an electricity market in which power is produced by generators, transmitted by transmission companies, and distributed by suppliers according to new trading agreements. The accurate forecasting of SMP can significantly influence the profit of market participants. In this paper, a new methodology for day-ahead SMP forecasting is proposed using the law of supply and demand on power. The salient feature of the proposed approach is that it exhibits excellent predicting performance in short-term forecasting.
Keywords: System Marginal Price (SMP); Price Forecasting; Short-term Forecasting

The reaction kinetics of the dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst was investigated using an isothermal integral reactor at 220–260°C temperature, 3–7 MPa pressure, and 1,000–2,500 mL/g·h space velocity. The H2/CO ratio of the synthetic gas was chosen between 3 : 1 and 6 : 1. The bi-functional catalyst was prepared by physically mixing commercial CuO/ZnO/Al2O3 and γ-alumina, which act as methanol synthesis catalyst and dehydration catalyst, respectively. The three reactions, including methanol synthesis from CO and CO2 as well as methanol dehydration, were chosen as independent reactions. The Langmuir-Hinshelwood kinetic models for dimethyl ether synthesis were adopted. Kinetics parameters were obtained using the Levenberg-Marquardt mathematical method. The model was reliable according to statistical and residual error analyses. The effects of different process conditions on the reactor performance were also investigated.
Keywords: Kinetics; Dimethyl Ether; Syngas; One-step; Fixed-bed

Ce X Zr1−X O2 catalysts were prepared by a sol-gel method, and H3PW12O40/Ce X Zr1−X O2 catalysts were then prepared by an impregnation method. Both catalysts were applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide in a batch reactor. NH3-TPD experiments were carried out to investigate the effect of acidity on the catalytic performance of Ce X Zr1−X O2 and H3PW12O40/Ce X Zr1−X O2. Catalytic performance of Ce X Zr1−X O2 and H3PW12O40/Ce X Zr1−X O2 was closely related to the acidity of the catalysts. The amount of dimethyl carbonate produced over both Ce X Zr1−X O2 and H3PW12O40/Ce X Zr1−X O2 catalysts increased with increasing acidity of the catalysts. This indicates that acidity of the catalyst played a key role in determining the catalytic performance of Ce X Zr1−X O2 and H3PW12O40/Ce X Zr1−X O2 in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Catalytic activity of H3 PW12O40/Ce X Zr1−X O2 was higher than that of the corresponding Ce X Zr1−X O2. The enhanced catalytic performance of H3 PW12O40/Ce X Zr1−X O2 was attributed to the Brønsted acid sites provided by H3PW12O40.
Keywords: Dimethyl Carbonate; Methanol; Carbon Dioxide; Heteropolyacid; Ceria-zirconia

Modification and characterization of amberlite XAD-2 with calcein blue for preconcentration and determination of copper(II) from environmental samples by atomic absorption spectroscopy by Elham Moniri; Homayon Ahmad Panahi; Meghdad Karimi; Nasir Ahmad Rajabi; Mohammad Faridi; Mahboobeh Manoochehri (1523-1531).
A chelating resin is produced by coupling a dye calcein blue to Amberlite XAD-2 through an azo spacer. The resulting resin has been characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studied for the preconcentration and determination of trace Cu(II) from solution samples. The optimum pH for adsorption of copper ions was 6. The sorption capacity of functionalized resin is 27 mg·g−1. The chelating resin can be reused for 10 cycles without any significant changes in sorption capacity. A recovery of 100% was obtained for Cu(II) when eluted with 0.5 M nitric acid. Scatchard analysis revealed that homogeneous binding sites were formed in the resin. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined 0.036, 2.196 and 0.348 at pH 6 and 20 °C, respectively. The method was applied for Cu(II) assay in environmental samples.
Keywords: Copper; Preconcentration; Solid Phase Extraction; Determination; Amberlite XAD-2; Isotherm Study

Removal of arsenic from aqueous solution using polyaniline/rice husk nanocomposite by Mohammad Soleimani Lashkenari; Behzad Davodi; Hossein Eisazadeh (1532-1538).
The present study deals with the adsorption of arsenic ions from aqueous solution on polyaniline/rice husk (PAn/RH) nanocomposite. Batch studies were performed to evaluate the influence of various experimental parameters like pH, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for arsenic removal were found to be pH 10, adsorbent dosage of 10 g/L and equilibrium time 30 minutes. Adsorption of arsenic followed pseudo-second-order kinetics. The equilibrium adsorption isotherm was better described by Freundlich adsorption isotherm model. The adsorption capacity (q max ) of PAn/RH for arsenic ions in terms of monolayer adsorption was 34.48 mg/g. The change of entropy (ΔS0) and enthalpy (ΔH0) was estimated at −0.066 kJ/(mol K) and −22.49 kJ/mol, respectively. The negative value of the Gibbs free energy (ΔG0) indicates feasible and spontaneous adsorption of arsenic on PAn/RH.
Keywords: Polyaniline; Rice Husk; Nanocomposite; Arsenic; Isotherm

Gasification of bamboo carbon with molten alkali carbonates by Choong-Gon Lee; Ho Hur (1539-1545).
Solid carbon can be used as a fuel in the direct carbon fuel cell (DCFC). The chemical oxidation of carbon with alkali carbonates was investigated in this work. Decreasing the weight ratio of carbon to carbonate from 5 g: 5 g to 5 g: 20 g had an insignificant effect on the amount and concentration of gases. However, changing the amounts from 5 g: 5 g to 20 g: 20 g tripled the total amount of gases produced with similar gas compositions. The gas compositions ranged from 62.2–67.5 mol% CO, 13.9–14.7 mol% H2, and 5.7–16.8 mol% CO2 at 800 °C. Thus CO was the dominant gas species in the conditions. With increasing temperature, CO generation was activated, especially over 700 °C. The carbonate species did not affect carbon oxidation. Steam was supplied to the carbon and carbonate mixture at a fixed flow rate of N2 or air. H2 was the highest composition at both cases.
Keywords: Gasification; Bamboo Carbon; Molten Carbonates; Nitrogen; Steam

Preparation and characterization of molybdenum trioxide from spent hydrodesulfurization catalyst by Barsha Dash; Indra Narayan Bhattacharya; Bhaskara Venkata Ramanamurthy; Raja Kishore Paramguru (1546-1549).
An approach to produce molybdenum trioxide from spent hydrodesulfurization (HDS) catalyst, obtained from a petroleum refinery, is presented here. The spent catalyst was devolatilized at 600 °C so as to make it free from oils, organics and other volatile species. It was then roasted with sodium carbonate at a temperature of 850 °C for 30 min. The leaching efficiency for 20% soda roasted sample at 10% pulp density was 99.8%. From the solution molybdenum was precipitated out as ammonium molybdate at pH 1.0 with HCl and ammonium chloride. This ammonium molybdate was calcined at 750 °C to get MoO3. The product was characterized by XRD. Its purity was determined titrimetrically and by ICP-AES.
Keywords: Spent Catalyst; Soda Roasting; Leaching; Molybdenum; Molybdenum Trioxide

Growth profile of predominantly Pseudomonas species was studied using wastewater containing phenol and m-cresol, as single and multi component systems in an internal loop airlift bioreactor (ILALR). The species utilized for the study was isolated from a wastewater treatment plant. The reactor was operated at both lower and higher hydraulic retention time (HRTs), 4.1 h and 8.3 h, respectively. The inlet phenol and concentration was varied between 100 and 800 mg/L with 800 mg/L as shock loading concentration for an HRT of 8.3 h. For 4.1 h HRT, the concentration was varied 100 and 500 mg/L using 500 mg/L as a shock loading concentration. The study showed complete degradation of both phenol and m-cresol, when present individually at an HRT of 8.3 h with an enriched biomass output. The specific growth rate of the culture at various phenol and m-cresol concentrations was fitted to a Monod model. The biokinetics value showed good potential of Pseudomonas species employing the internal loop air lift bioreactor in utilizing high strength phenolics containing wastewater. Culture growth profile with both phenol and m-cresol as mixtures also showed decreased lag times with complete utilization of the phenolics.
Keywords: Biomass; Internal Loop Airlift Bioreactor; Monod Model; Phenolics; Pseudomonas sp.; Wastewater

The removal of low concentration formaldehyde over sewage sludge char treated using various methods by Ji Young Lee; Sung Hoon Park; Jong-Ki Jeon; Kyung-Seun Yoo; Seung-Soo Kim; Young-Kwon Park (1556-1560).
Sewage sludge char was activated, using several different methods, to be used for the adsorption of formaldehyde. First, sewage sludge was pyrolyzed at 700 °C for one hour to produce char. The sewage sludge char was then activated with 20% steam gas. To produce a chemically activated char, KOH was used with the char at a weight ratio of KOH/char=0.5. To produce another kind of activated char containing nitrogen functional groups, the sewage sludge char was activated with ammonia at 350 °C. These activated chars were used for indoor low concentration formaldehyde adsorption experiments. All the chars tested in this study were shown to have better performance than activated carbon. In particular, the char activated with both ammonia and KOH showed the best formaldehyde adsorption performance. This result was attributed to the combination of surface basicity due to large amounts of metal components and generation of oxygen and nitrogen functional groups as a result of the KOH and ammonia treatments.
Keywords: Activated Sewage Sludge Char; Low Concentration Formaldehyde; Indoor Air

A microwave-assisted extraction (MAE) method was used to recover the anticancer agent paclitaxel from plant cell cultures, and the extraction efficiency of the paclitaxel was determined using various organic solvents (acetone, chloroform, ethanol, methanol, and methylene chloride) and solvent concentrations. Methanol provided the highest recovery of paclitaxel (∼93%) and resulted in the most severe rupturing of the biomass surface during MAE. Most of the paclitaxel (>99%) was recovered using a methanol concentration of 90% (water content: 10%), suggesting that the addition of a small amount of water improves the efficiency of MAE. Furthermore, analysis of the surface of the biomass using an electron microscope revealed that the higher the recovery of paclitaxel, the more severe the damage to the biomass surface. A comparison of the extraction efficiency between MAE and conventional solvent extraction (CSE) showed that with CSE, only up to 54% of the paclitaxel could be recovered in one extraction whereas with MAE, most of the paclitaxel (>99%) in the biomass could be recovered in one extraction.
Keywords: Paclitaxel; Recovery; Microwave-assisted Extraction (MAE) Efficiency; Water Content of Solvent; Plant Cell Cultures

Efficient production of glutathione using hydrolyzate of banana peel as novel substrate by Xue-Dong Chen; Gong-Yuan Wei; Jun-Li Zhang; Ying-Ying Dong (1566-1572).
The hydrolyzate of banana peels containing abundant fermentable sugars as glucose, xylose, mannose, and arabinose was successfully used as a novel substrate for the efficient production of glutathione by Candida utilis SZU 07-01. Xylose was first selected as the sole carbon source for glutathione production, medium optimization for better cell growth and higher glutathione using response surface methodology consisting of PB design, the steepest ascent experiment and CCD was carried out, and the optimal combination of nutrients was obtained as follows: xylose 20 g/L, (NH4)2SO4 9.59 g/L, KH2PO4 3 g/L, L-methionine 5.72 g/L and MgSO4 0.20 g/L. The maximum dry cell weight and glutathione achieved using the optimized medium were 7.36 g/L and 154.32 mg/L, respectively. Following with the content in this medium, other sugars like glucose, mannose and arabinose were chosen as the sole carbon source and all tested available for glutathione production. Based on these results, the hydrolyzate of banana peels was selected as a novel substrate, and a high DCW of 7.68 g/L and glutathione yield of 111.33 mg/L were obtained with the initial sugar concentration of 20 g/L in the hydrolyzate of banana peels.
Keywords: Glutathione; Candida utilis ; Banana Peel; Hydrolyzate; Fermentable Sugars; Response Surface Methodology

Recombinant protein secretion via the type III secretion system by Le Tam Dinh Vo; Soon Ho Hong (1573-1579).
The type III secretion system (T3SS) is a mechanism by which bacteria export proteins from the cytoplasm, through the membranes, to the extracellular environment. T3SS is made up of more than 20 different proteins, about half of which maintain conserved sequences. This review summarizes the features of this novel apparatus and discusses the potential of utilizing T3SS to export recombinant proteins into the external environment, and the impact this system will have on protein production technology.
Keywords: Type III Secretion System (T3SS); Secretion; Recombinant Protein

The optimal conditions of the downstream process for recovery of pullulan produced by Aureobasidium pullulans HP-2001 were examined using response surface method (RSM). The optimal amount of diatomite in filter press and the optimal flow rate in a continuous flow centrifuge for removal of cells from the culture broth of A. pullulans HP-2001 were found to be 5.0% (v/v) and 2.0 L/min. Based on central composite design (CCD) experiments and analysis of variance (ANOVA) indicated that the optimal conditions for recovery of pullulan from the supernatant by precipitation were the volume ratio of ethanol (or isopropanol) to supernatant of 3.0: 1.0, the reaction time of 29.5 h, and the reaction temperature of 20.2 °C. The expected maximal recovery yields of pullulan using ethanol and isopropanol under optimized conditions were 79.2 and 85.5%, respectively.
Keywords: Pullulan; Down-stream Process; Filter Press; Continuous Flow Centrifuge; Response Surface Method

Effects of carbon source and metabolic engineering on butyrate production in Escherichia coli by Sea-Mi Joung; Nagendra Prasad Kurumbang; Byoung-In Sang; Min-Kyu Oh (1587-1592).
Butyrate was produced in recombinant Escherichia coli strains by applying metabolic engineering strategies. The genes for producing butyrate were cloned from Clostridium acetobutylicum and then expressed in E. coli. To study important factors for improving the productivity of butyrate, we deleted pta and ptsG genes in E. coli and compared the effects of these gene deletions in E. coli B and K strains. The effect of carbon sources, glucose and glycerol, was also compared. A significant improvement of butyrate production was made when glycerol was used as a carbon source, resulting in 0.56 g/l of butyrate in LB medium with 1% (v/v) glycerol.
Keywords: Escherichia coli ; Clostridium acetobutylicum ; Butyrate; Metabolic Engineering

A commercial tubular zeolite membrane (NaA) was employed in a vapor permeation system to dehydrate the reaction mixture during the esterification of propionic acid with isopropanol. The reaction was performed in a batch reactor, using Amberlyst 15 as a catalyst with different weight fractions relative to propionic acid. Experiments were conducted to investigate the effect of the alcohol-to-acid molar ratio on the performance of the hybrid process. The integration of the chemical reaction with the vapor permeation process significantly enhanced the conversion of the reversible esterification reaction. It was observed that contrary to the effect of increasing alcohol-to-acid molar ratio from 1: 1 to 1.5: 1, the acid conversion and the permeated water flux decreased when the reactants molar ratio increased from 1.5: 1 to 3: 1. This effect was due to the reducing effect of reaction mixture composition on the boiling point and reaction and evaporation rates during the hybrid process. Also, increasing catalyst loading had noticeable influence on the acid conversion and the permeated water flux.
Keywords: Esterification; Isopropyl Propionate; Membrane Reactor; Vapor Permeation; Zeolite Membrane

A multi-fluid Eulerian computational fluid dynamics (CFD) model is used to simulate the entrainment of fluid catalytic cracking (FCC) particles in gas-solid fluidized beds. Entrainment of Geldart A group particles was studied because of their wide range of industrial use. The model was based on the kinetic theory of granular flow. The CFD model was used to investigate the effect of column diameter on the entrainment flux of particles in a binary mixture. Two different sizes of particles were used because many engineering applications deal with binary mixture of particles in fluidized beds. Various column diameters, including 38 mm, 76 mm, 114 mm, 152 mm, and 190 mm, were investigated. The entrainment flux of particles was increased with decreasing column diameter. The effect of column diameter was not significant for column diameters larger than 114 mm. Furthermore, increasing the superficial gas velocity increased the entrainment flux of particles. Model predictions were also compared with experimental findings.
Keywords: Entrainment; Fluidized Bed; CFD; Column Diameter; FCC

Extraction and separation of D/L-lactic acid in simulated fermentation broth by Jun Zhou; Wentao Bi; Kyung Ho Row (1608-1612).
The recovery of lactic acid from fermentation broth plays an important part in production of lactic acid. In this case, the extraction of lactic acid from simulated fermentation broth was processed by tri-n-octylamine dissolved in oleyl alcohol. The extraction efficiency was investigated with several variables, and the optimal condition of extraction of lactic acid (10 mg mL−1) from aqueous solution was tri-n-octylamine/oleyl alcohol (30/70, v/v) and solvent phase/ fermentation (1/2, v/v) stirred for 60 min under room temperature. The optimal back extraction of lactic acid was obtained by hot water (∼90 °C) with solvent phase/water (1/4, v/v). The back extracted racemic lactic acid was direct enantiomeric analyzed and separated by chiral ligand chromatography due to strict requirement of absolute configuration in pharmaceutical field and food science. The effect of various parameters on enantioselectivity was discussed and the (L)-phenylalaninamide·HCl (6.0 mmol L−1) and CuSO4·5H2O (3.0 mmol L−1) dissolved in methanol/water (5/95, v/v) at pH=6.0 was the suitable mobile phase for chiral ligand exchange separation of (D, L)-lactic acids. By the investigations, a convenient systemic method was established for extraction and separation of (D, L)-lactic acid.
Keywords: Lactic Acid; Fermentation; Extraction; Separation; Ligand Exchange

Systems consisting of light components and heavy hydrocarbons are highly asymmetric and industrially important. Design and control of facilities for separation and purification of such mixtures require vapor-liquid equilibrium data. Coupling of the cubic equation of state (EOS) with excess Gibbs energy models (EOS/G ex models) failed to represent the vapor-liquid equilibria (VLE) of such systems accurately. The main purpose of this work is to present a modification of Wong-Sandler mixing rule with using the composition dependent binary interaction parameter. Vaporliquid equilibria for 30 binary systems are calculated using the SRK equation of state with proposed model and Wong-Sandler mixing rule. Calculated pressures and mole fractions of vapor phase are compared with experimental data. The average absolute percentage deviation indicates that error involved in the application of modified Wong-Sandler model is less than Wong-Sandler model in most cases.
Keywords: Vapor-liquid Equilibrium; Wong-Sandler Mixing Rule; Asymmetric Systems

Investigation of cleaning solution composed of citric acid and 5-aminotetrazole by Oh Joong Kwon; Jae Han Bae; Bum Koo Cho; Yung Jun Kim; Jae Jeong Kim (1619-1624).
In a damascene process for a copper metallization, the planarization method based on a chemical mechanical polishing (CMP) has been used for multilevel metallization. Although a buffing step was adopted in this CMP process, numerous residual abrasives, capable of increasing the resistance of copper lines, still existed after the second CMP step. For this reason, more research has focused on identification of an effective cleaning solution. We investigated a new cleaning solution consisting of citric acid and 5-aminotetrazole (ATRA) as a complexing agent and corrosion inhibitor, respectively. The citric acid was added to achieve a lift-off effect by removing the underlying copper oxide layer, whereas the ATRA was adopted to prevent abrasive re-adsorption by forming a passivation layer on the copper surface. The cleaning solution consisting of 0.006 M citric acid and 0.006 M ATRA displayed a particle density of 0.07 #/μm2 in an immersion test, and no particles were observed on a 4 cm2 coupon wafer in a real process test at pH 12.
Keywords: Cleaning Solution; Citric Acid; 5-Aminotetrazole; Particle Density; Etch Rate

Controlling the morphology of trioctyl phosphine oxide-coated cadmium selenide/poly 3-hexyl thiophene composite active layer for bulk hetero-junction solar cells by Nguyen Tam Nguyen Truong; Matthew Lowell Monroe; Umme Farva; Timothy James Anderson; Chinho Park (1625-1631).
Bulk hetero-junction solar cells with CdSe nanoparticles-P3HT (poly 3-hexyl thiophene) composite active layer were fabricated, and the control of morphological feature of the nanoparticle-polymer composite thin films was investigated. A binary solvent composed of a primary solvent with intermediate polarity and a secondary solvent with high polarity was found to be effective in controlling the dispersion of the CdSe nanocrystals in the P3HT matrix, and the modification of the nanocrystal surface by liquid-liquid extraction process was found to be effective in achieving the desired composite film morphology. Surface roughness of the active layer was optimized for various loadings of CdSe nanoparticles and could be reproducibly controlled to less than 10 nm.
Keywords: Bulk Hetero-junction Solar Cell; Active Layer; CdSe Quantum Dot; Conjugated Polymer; Nanoparticle Dispersion

In spite of the importance of monomer concentration measurement in polymerization, it is difficult to measure the concentration in thin film polymerization, such as the UV photopolymerization of acrylates. A small device, a quartz crystal resonator, has been applied to the measurement of monomer amount in the UV photopolymerization of trimethylolpropane triacrylate with an initiator of 2-ethylanthraquinone. The resonant resistance of the resonator is converted to the monomer concentration using an empirical relationship. The measurement results indicate that the proposed technique is effective for determining the monomer concentration. The simplicity and ready availability of the proposed application have been proven experimentally.
Keywords: UV Photopolymerization; On-line Monitoring; Quartz Crystal Resonator

Drying characteristics of sewage sludge by Jiang Qian; Yeong Woo Yoon; Pil Sang Youn; Ji Hye Kim; Don Sun Choi; Jeong-Hoo Choi; Young Chan Choi; Bongjin Jung (1636-1640).
To obtain the drying rate of sewage sludge for use in design of a conductive indirect-heating dryer with agitation, the drying characteristics of sewage sludge from three different wastewater treatment plants were investigated with a thermogravimetric analyzer (TGA) in isothermal conditions. Temperature and sample mass were considered as experimental variables. The drying mechanism agreed well with the shrinking core model dominated by the kinetic rate. The activation energy of drying was 17.30 kJ/g mol. A rate equation was proposed for drying of sewage sludge.
Keywords: Drying; Rate; Activation Energy; Sewage Sludge