Korean Journal of Chemical Engineering (v.30, #10)

Toxic chemical monitoring of agricultural bioproducts using nanomaterials-based sensors by Syed Rahin Ahmed; Kwangnak Koh; Enoch Y. Park; Jaebeom Lee (1825-1832).
Owing to the fast growth of the agricultural bioproducts industry, which requires its products to be fresh and visibly appealing, the increased use of imidacloprid pesticides has raised deep concerns about environmental effects, food quality, and the toxicity of residues. This has led to the development of various extraction methods of biochemicals and chemicals and their effective sensors for monitoring pesticide residues. We review the current commercial and nanotechnology-adopted techniques available in order to draw attention to the primary issues in the development of novel extraction and sensing systems using nanotechnology.
Keywords: Imidacloprid; Chloronicotinic Pesticides; Agriculture; Chemical Sensor; Nanotechnology; Extraction

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures was performed using cobalt ammonium sulfate as a structure-directing agent, and the effect of the concentration of cobalt ammonium sulfate on the characteristics of the tungsten oxide nanostructures was investigated. XRD measurements showed that hexagonal tungsten oxide (h-WO3) structures were obtained at a higher concentration of cobalt ammonium sulfate (0.2 M), while cubic tungsten oxide (c-WO3) structures were obtained at a lower concentration of cobalt ammonium sulfate (0.01M). Mixed structures of h-WO3 and c-WO3 were observed at an intermediate concentration of cobalt ammonium sulfate. Morphological studies revealed that h-WO3 appeared as nanowires with a diameter of about 40 nm and an average length of 1 μm. c-WO3 was shaped in pillar-like nanorods with a diameter of about 30 nm. A red-shift in the UV/Vis absorption peak was observed with different phases of tungsten oxide nanostructures.
Keywords: Hydrothermal; Tungsten Oxide; Nanostructures; Structure-directing Agent

l-glutamic acid can be crystallized as metastable α-form and stable β-form crystal. The α-form is desired because of its prismatic shape. Production of α-form of l-glutamic acid by cooling crystallization is not well-defined and α-form solid is commercially not available. In this study, an optimal cooling strategy to selectively produce large and narrowly distributed α-crystals is found by modeling and optimizing the crystallization and polymorphic transformation of l-glutamic acid. The optimal temperature profile is found to be cooling-heating-cooling concept where short nucleation period is followed by growth period in metastable zone. The obtained α-form of L-glutamic acid by optimal strategy had improved mean size, distribution, and purity compared to constant cooling.
Keywords: Cooling Crystallization; Population Balance Model; Polymorphic Transformation; l-Glutamic Acid; Optimization

Mixing of two stratified miscible fluids in an eccentric stirred tank agitated by a four pitched-blade turbine was studied by using the detached eddy simulation (DES) model and volume of fluid (VOF) method. The fluids were operated in the transitional and mildly turbulent flow regimes. Interfaces between the two miscible fluids during the mixing processes were captured and mixing times were computed. Effects of the Richardson number and eccentricity on the mixing times were quantificationally analyzed. Results show that the spatial and temporal variations of volume fractions of the fluids can be well captured by the method presented in this study. Mixing time increases with the increase of Richardson number. Effect of eccentricity on mixing time depends on Richardson number and the eccentric agitation scheme is not advisable to use to blend the low-viscosity miscible fluids starting from a stratified state, especially for lower Richardson values.
Keywords: Stirred Tank; Stratification; Miscible Fluids; Mixing; Detached Eddy Simulation (DES); Volume of Fluid (VOF)

TiO2 nanoparticles were synthesized by the P-25 powder modified sol-gel method under different TTIP (Titanium tetraisopropoxide) concentrations, P-25 loading and the gelation pHs. Structural properties of nanoparticles were characterized by XRD, FESEM and BET analysis. Results show that crystallinity level, particle size and the surface area are a function of P-25 loading and gelation pH, whereas TTIP concentration affects only the crystalline composition. Response surface methodology based on central composite design was used to optimize these synthesis parameters in photodegradation of Acid Red 73. The degradation efficiency was significantly affected by P-25 loading, pH value of gelation and the interaction effect between TTIP concentration and P-25 loading. The optimal values of parameters were found to be a pH of 1.34, a TTIP concentration of 0.25M and a P-25 loading of 39.76 g/L. At optimal synthesis conditions, TiO2 film was coated on alumina foam and its structural properties were characterized by XRD, SEM and BET technique. The photocatalytic activity of the as-prepared films was found to be higher than that of the films prepared by the sol-gel method and those made from the slurries of P-25. The reasonable photocatalytic performance and good stability offered by the optimized film make it as an effective alternative for large application of water treatment.
Keywords: Titanium Dioxide; Modified Sol-gel Method; Structural Properties; Response Surface Methodology; Immobilization on Alumina Foam

Development of a model for dimethyl ether non-adiabatic reactors to improve methanol conversion by Fatemeh Nasrollahi; Gholamreza Bakeri; Ahmad Fauzi Ismail; Mostafa Rahimnejad; Mahdi Imanian (1867-1875).
The modeling of adiabatic and non-adiabatic reactors, using three cooling mediums in the shell side of a shell and tube reactor in cocurrent and countercurrent flow regimes has been conducted. The cooling mediums used in this research are saturated water and methanol feed gas to a reactor which is preheated in the shell side and a special type of oil. The results of adiabatic reactor modeling show good compatibility with the data received from a commercial plant. The results of non-adiabatic reactor modeling showed that more methanol conversion can be achieved in a lower length of reactor, even though in some cases the maximum temperature in the tube side of the reactor is more than the deactivation temperature of the catalyst.
Keywords: Dimethyl Ether; DME; Modeling; Non-adiabatic Reactor; Shell and Tube Reactor

A significant enhancement in the catalytic activity of Au/TiO2 in CO oxidation and preferential oxidation reaction by creating the active sites on the catalyst surface by thermal treatment as well as by producing small gold particles by plasma treatment has been studied. Au/TiO2 catalyst (Au (1 wt%) supported on TiO2) was prepared by conventional deposition-precipitation method with NaOH (DP NaOH) followed by washing, drying and calcination in air at 400 °C for 4 h. Thermal treatment of Au/TiO2 was carried out at 550 °C under 0.05 mTorr. A small amount of Au/TiO2 catalyst was taken from the untreated and thermally treated Au/TiO2 and both kinds of catalysts were treated with plasma sputtering at room temperature. The activity of the catalysts has been examined in the reaction of CO oxidation and preferential oxidation (PROX) at 25–250 °C. Thermally treated Au/TiO2 showed better catalytic activity as compared to the untreated catalyst. There is also an additional enhancement in the catalytic activity due to plasma sputtering on the both kinds of catalysts. Thermally treated Au/TiO2 followed by plasma sputtering Au/TiO2 showed higher conversion rates for CO oxidation reaction compared with untreated, thermally treated and plasma sputtered Au/TiO2 catalysts. It may be concluded that the enhancement of catalytic activity of thermally treated Au/TiO2 followed by plasma sputtering is owing to the generation of active sites such as oxygen vacancies/defects in TiO2 support using thermal treatment as well as by producing small gold particles using plasma treatment.
Keywords: Catalytic Activity; Au/TiO2 Catalyst; CO Oxidation; Thermal and Plasma Treatment

We suggest a 2D-plot representation combined with life cycle greenhouse gas (GHG) emissions and life cycle cost for various energy conversion technologies. In general, life cycle assessment (LCA) not only analyzes at the use phase of a specific technology, but also covers widely related processes of before and after its use. We use life cycle GHG emissions and life cycle cost (LCC) to compare the energy conversion process for eight resources such as coal, natural gas, nuclear power, hydro power, geothermal power, wind power, solar thermal power, and solar photovoltaic (PV) power based on the reported LCA and LCC data. Among the eight sources, solar PV and nuclear power exhibit the highest and the lowest LCCs, respectively. On the other hand, coal and wind power locate the highest and the lowest life cycle GHG emissions. In addition, we used the 2D plot to show the life cycle performance of GHG emissions and LCCs simultaneously and realized a correlation that life cycle GHG emission is largely inversely proportional to the corresponding LCCs. It means that an expensive energy source with high LCC tends to have low life cycle GHG emissions, or is environmental friendly. For future study, we will measure the technological maturity of the energy sources to determine the direction of the specific technology development based on the 2D plot of LCCs versus life cycle GHG emissions.
Keywords: 2D Projection; Life Cycle Analysis (LCA); Life Cycle Cost (LCC); Electricity Conversion; Coal; Natural Gas; Nuclear Power; Hydro Power; Geothermal Power; Wind Power; Solar Thermal Power; Solar Panel

Arsenic removal from drinking water by electrocoagulation using iron electrodes by Ceren Ucar; Meltem Bilici Baskan; Aysegul Pala (1889-1895).
Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm−2), initial arsenic concentration (50–500 μg L−1), operating time (0–15 min), electrode surface area (266–665 cm2), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L−1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm−2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm2 taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L−1 for electrode surface area of 266 cm2. The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.
Keywords: Arsenic; Electrocoagulation; Drinking Water; Iron Electrodes; Iron Concentration

Desorption kinetics of polycyclic aromatic hydrocarbons in soil using lab-scale rotary desorber by Soo-Bin Jeon; Min-Chul Kim; Jun-hyung Cho; Jong-Hyeon Jung; Kwang-Joong Oh (1896-1903).
Thermal desorption of fluorene, anthracene, pyrene, and benzo(a)pyrene in soil contaminated with PAHs was performed using a rotary desorber at temperatures of 300–500 °C, and the dependency of the PAH removal efficiency on the percentage water content, residence time, and thermal desorption temperature was investigated. The removal efficiencies were inversely proportional to the boiling points of PAHs, and the removal efficiencies decreased with decreasing residence time and heating temperature. The reaction rate constant and activation energies (E A ) were estimated to determine the thermal desorption properties of each substance, and the activation energies were found to be 29.50–34.48 kJ mol−1. Freeman-Carroll’s law was applied along with the Arrhenius equation to extract the thermal desorption properties from the data obtained in this experiment.
Keywords: PAHs; Thermal Desorption; Rotary Desorber; Desorption Kinetic; Activation Energy

Surface chemistry and adsorption mechanism of cadmium ion on activated carbon derived from Garcinia mangostana shell by Yee Li Kang; Mei Yi Poon; Purushothaman Monash; Shaliza Ibrahim; Pichiah Saravanan (1904-1910).
A detailed surface characterizations and adsorption mechanism of Cd2+ on chemical activated carbon (CAC) prepared from Garnicia mangostana shell were investigated. The activation is accomplished in self-generating atmosphere using phosphoric acid as activating agent. The characterizations performed are elemental analysis, functional group identification, N2 adsorption isotherm and surface charges. Adsorption mechanism of metal ion was tested using Cd2+ as model ion. CAC achieved BET surface area of 1,498 m2/g with a mixture of micro and mesopores. The point of zero charge is observed to be at pH 2.8 and the optimum pH for Cd2+ adsorption on CAC is 12. The adsorption isotherm followed the Freundlich model, and the adsorption kinetics was explained by pseudo-second order kinetic model. From thermodynamic studies, the adsorption was found to be physical adsorption. X-ray photoelectron spectroscopy (XPS) confirmed the adsorption of Cd2+ onto CAC as +2 oxidation state.
Keywords: Garcinia mangostana ; Activated Carbon; Adsorption Mechanism; Surface Chemistry

The mixed liquor of organic wastes (MLOW) produced from a 1,4-butanediol production process was tested as an external carbon source for denitrification in the biological nutrient removal (BNR) process. The fraction of non-biodegradable chemical oxygen demand (NBDCOD) in the MLOW was estimated to be approximately 0.2% by measuring the oxygen uptake rate (OUR). The specific denitrification rate (SDNR) of MLOW and methanol from a nitrate utilization rate (NUR) test was confirmed to be approximately 13.02 and 12.68 mgN/gVSS/hr, respectively. The results indicated that the denitrification capability of microorganisms applying the MLOW was similar to that of using methanol as an external carbon source for the BNR process. The feasibility of MLOW for a stainless steel wastewater treatment plant (WWTP) was investigated. The low concentration of effluent nitrogen indicated a denitrification capability for MLOW similar to that for methanol. These results support the potential of MLOW as a substitute for methanol in the BNR process.
Keywords: Organic Waste; 1,4-Butanediol; Denitrification; External Carbon Source; Wastewater Treatment Plant

Biofiltration of volatile organic compound using two packing materials: Kinetics and modelling by Viswanathan Saravanan; Manivasagan Rajasimman; Natarajan Rajamohan (1918-1928).
The performance of two laboratory scale biofilters, packed with pressmud (BF1) and sugarcane bagasse (BF2), was evaluated for gas phase ethylacetate removal under various operating conditions. Biofilters were inoculated with mixed culture obtained from pharmaceutical wastewater sludge. Experiments were carried out at different flow rates (0.03, 0.06, 0.09 and 0.12 m3 h−1) and inlet ethylacetate concentrations (0.2, 0.4, 0.6 and 1.2 gm−3). Maximum removal efficiency (RE) of 100% and 98% was achieved at an inlet concentration of 0.2 gm−3 and gas flow rate of 0.03 m3 h−1 in BF1 and BF2, respectively. A maximum elimination capacity (EC) of 66.6 gm−3 h−1 and 64.1 gm−3 h−1 was obtained in BF1 and BF2, respectively, at an inlet concentration of 0.8 gm−3 and a gas flow rate of 0.12 m3 h−1. The kinetics of biofiltration of ethylacetate was studied by using Ottengraf and van den Oever model. The kinetic modelling gives an insight into the mechanism of biofiltration. The modified Ottengraf model, which was also tested, demonstrated good agreement between calculated and experimental data.
Keywords: Ethylacetate; Biofiltration; Ottengraf and van den Oever Model; Pressmud; Sugarcane Bagasse; Gas Flow Rate

Hot water extracts, KIOM-C and KIOM-MA-128, were formulated into tablets and three kinds of absorption enhancers were included in the tablets. The mixture of starch and lactose was used as an excipient, sodium carboxymethylcellulose as a disintegrating agent, and magnesium stearate as a binder. The weight ratio of water extract/excipient/disintegrating agent/absorption enhancer/binder was 80/7/10/2/1. The tablets were completely disintegrated in an aqueous solution in 40min, and the disintegration rates were almost the same with all the tablets tested. Among the enhancers, EDTA was the most effective in enhancing the in vitro small intestine absorption of KIOM-C and KIOM-MA-128.
Keywords: KIOM-C, KIOM-MA-128; Tablet; Disintegration; Small Intestine Absorption; pH Stability

A comparative study on antibody immobilization strategies onto solid surface by Ji Eun Lee; Jeong Hyun Seo; Chang Sup Kim; Yunkyeoung Kwon; Jeong Hyub Ha; Suk Soon Choi; Hyung Joon Cha (1934-1938).
Antibody immobilization onto solid surface has been studied extensively for a number of applications including immunoassays, biosensors, and affinity chromatography. For most applications, a critical consideration regarding immobilization of antibody is orientation of its antigen-binding site with respect to the surface. We compared two oriented antibody immobilization strategies which utilize thiolated-protein A/G and thiolated-secondary antibody as linker molecules with the case of direct surface immobilization of thiol-conjugated target antibody. Antibody immobilization degree and surface topography were evaluated by surface plasmon resonance and atomic force microscope, respectively. Protein A/G-mediated immobilization strategy showed the best result and secondary antibody-mediated immobilization was the worst for the total immobilization levels of target antibodies. However, when considering real-to-ideal ratio for antigen binding, total target antigen binding levels (oriented target antibody immobilization levels) had the following order: secondary antibody-mediated immobilization>protein A/G-mediated immobilization>direct thiol-conjugated immobilization. Thus, we confirmed that protein A/G- and secondary antibody-mediated strategies, which consider orientation of target antibody immobilization, showed significantly high antigen binding efficiencies compared to direct random immobilization method. Collectively, the oriented antibody immobilization methods using linker materials could be useful in diverse antibody-antigen interaction-involved application fields.
Keywords: Antibody Immobilization; Orientation; Thiolation; Protein A/G; Secondary Antibody; Surface Plasmon Resonance; Atomic Force Microscopy

Nucleation behavior of glutathione polymorphs in water by Zhi Chen; Leping Dang; Shuai Li; Hongyuan Wei (1939-1945).
Nucleation behavior of glutathione (GSH) polymorphs in water was investigated by experimental method combined with classical nucleation theory. The solubility of α and β forms GSH in water at different temperatures, and the nucleation induction period at various supersaturations and temperatures were determined experimentally. The results show that, in a certain range of supersaturation, the nucleation of β form predominates at relatively higher temperature, while α form will be obtained at lower temperature. The nucleation kinetics parameters of α and β form were then calculated. To understand the crucial role of temperature on crystal forms, “hypothetic” nucleation parameters of β form at 283.15 K were deduced based on extrapolation method. The results show that the interfacial tension, critical free energy, critical nucleus radius and nucleus number of α form are smaller than that of β form in the same condition at 283.15 K, which implies that α form nucleates easier than β form at low temperature. This work may be useful for the control and optimization of GSH crystallization process in industry.
Keywords: Glutathione; Nucleation; Induction Period; Crystallization; Classical Nucleation Theory

Modeling and simulation of solvent extraction processes for purifying rare earth metals with PC88A by Kyung Hwan Ryu; Changkyu Lee; Go-Gi Lee; Sungkoo Jo; Su Whan Sung (1946-1953).
A new simulation logic and thermodynamic equilibrium analysis algorithm combined with a new model simplification technique was developed to simulate the solvent extraction process for purifying rare earth metals from chloride solution with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A) as a solvent. The proposed model simplification method significantly reduces the number of the nonlinear equilibrium equations to be simultaneously solved to overcome the initial guess problem and obtain numerically stable convergence pattern in solving the equilibrium analysis problem and performing the rigorous simulation of the extraction process. A new equilibrium analysis algorithm on the basis of the simplified nonlinear equilibrium equations is also proposed to estimate the equilibrium concentrations by solving the rigorous first principle extraction model. Finally, a solvent extraction simulator is developed to estimate all the concentrations of all the stages of the solvent extraction process by solving the equilibrium analysis problem at each stage in a sequential way. The proposed simulator doe not suffer from the initial guess problem and shows very robust convergence pattern without any numerical problems.
Keywords: Solvent Extraction; PC88A; Rare Earth; Distribution Coefficient; Simulation; Equilibrium Analysis; Model Simplification

We systematically examined the effect of the solvent system (methanol/water or acetone/pentane) on precipitation characteristics and mechanisms in the increased surface area precipitation (ISAP) with different ion exchange resins for the purification of paclitaxel. When Amberlite IRA 400Cl was added to increase the surface area, the acetone/ pentane system was found to be more effective than the methanol/water system in terms of paclitaxel purity. The addition of surface area-increasing materials increased the yield in the methanol/water system, whereas it decreased the yield in the acetone/pentane system. Precipitates in the methanol/water system were needle-shaped or star-shaped, spreading from the central nucleus along the growing branches, while precipitates in the acetone/pentane system were disk shaped, branching out from around the nucleus. When Amberlite IRA 400Cl was added, it was possible to obtain smaller paclitaxel precipitates in the acetone/pentane system than in the methanol/water system.
Keywords: Paclitaxel; Precipitation; Characteristics; Solvent System; Ion Exchange Resin

The formation of cysteamine layer on gold surfaces may have an effect on the distribution of either gold particle adsorbed to the ZrO2 surface or vice versa with the adjustment of the electrostatic interactions. The atomic force microscope (AFM) was used to measure the surface forces between the zirconia surface and the cysteamine surface s as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface.
Keywords: Cysteamine; Gold Surface; ZrO2 Surface; AFM; DLVO Theory

Thermal stability and degradation of chitosan modified with phenylacetic acid by Mostafa Amin Diab; Adel Zaki El-Sonbati; Ibrahim Mohi El-dien; Dina Mohamed Diaa Bader (1966-1971).
N-(phenylacetyl) chitosan (NPAC) polymer was synthesized by the reaction of phenylacetic acid with chitosan. The chemical structure of the formed polymer was characterized by IR and microanalysis. Thermogravimetric analysis revealed that the thermal stability of the NPAC polymer was less than that of chitosan. The products of NPAC thermal degradation were identified by the GC-MS technique. The results indicate that the mechanism of degradation of NPAC polymer is characterized by the elimination of low-molecular weight radicals. A combination of these radicals and a random scission mechanism along the backbone chain are the main source of the degradation products.
Keywords: N-(phenylacetyl) Chitosan; Thermal Stability; Mechanism of Degradation