Korean Journal of Chemical Engineering (v.34, #1)

Hydrotalcite was synthesized from hydroxide-form precursors to prepare a novel high-temperature CO2 sorbent, and the effect of Mg/Al ratio on CO2 sorption was studied. To enhance the CO2 sorption capacity of the sorbent, K2CO3 was coprecipitated during the synthetic reaction. X-ray diffraction analysis indicated that the prepared samples had a well-defined crystalline hydrotalcite structure, and confirmed that K2CO3 was successfully coprecipitated in the samples. The morphology of the hydrotalcite was confirmed by scanning electron microscopy, and N2 adsorption analysis was used to estimate its surface area and pore volume. In addition, thermogravimetric analysis was used to measure its CO2 sorption capacity, and the results revealed that the Mg: Al: K2CO3 ratio used in the preparation has an optimum value for maximum CO2 sorption capacity.
Keywords: Hydrotalcite; Sorption; CO2 Sorbent; K2CO3 Promotion; Hydrothermal Synthesis

Performance assessment and system optimization of a combined cycle power plant (CCPP) based on exergoeconomic and exergoenvironmental analyses by Minhyun Kim; Dongwoo Kim; Iman Janghorban Esfahani; Seungchul Lee; Minjeong Kim; Changkyoo Yoo (6-19).
We propose a systematic approach for performance evaluation and improvement of a combined cycle power plant (CCPP). Exergoeconomic and exergoenvironmental analyses are used to assess CCPP performance and suggest improvement potentials in economic and environmental aspects, respectively. Economic and environmental impacts of individual system components are calculated by cost functions and life cycle assessments. Both analyses are based on a CCPP case study located in Turkey, which consists of two gas turbine cycles and a steam turbine cycle with two different pressure heat recovery units. The results of the exergoeconomic analysis indicate that the combustion chamber and condenser have a high performance improvement potential by increasing capital cost. Furthermore, the exergoenvironmental analysis shows that the exergy destruction of the steam turbine and combustion chamber and/or the capacity of heat recovery units must be reduced in order to improve environmental performance. This study demonstrates that combined exergoeconomic and exergoenvironmental analyses are useful for finding improvement potentials for system optimization by simultaneously evaluating economic and environmental impacts.
Keywords: Life Cycle Assessment (LCA); Combined Cycle Power Plant (CCPP); Exergoeconomic; Exergoenvironmental; Improvement Potential

Modeling and simulation of drying characteristics on flexible filamentous particles in rotary dryers by Conghui Gu; Chao Zhang; Xin Zhang; Naihong Ding; Bin Li; Zhulin Yuan (20-28).
Experiments were conducted to demonstrate the effects of the drum wall temperature on the heat and mass transfer in rotary dryers. The drying characteristics of flexible filamentous particles in rotary dryers were further explored. In addition, the inlet and outlet temperatures and moisture contents of granular particles were measured. As a result, the good agreement between the simulations and experiments verified the rationale and feasibility of the numerical method. Therefore, the approach was adopted to evaluate the temperature and moisture content of wet granular particles in a rotary dryer in different conditions, for instance, drum wall temperature and rotational speed. The results revealed that the higher drum wall temperature led to hotter particles with lower outlet moisture content. Conversely, the higher rotational speed resulted in cooler particles with higher outlet moisture content due to the decrease of residence time in the rotary dryer.
Keywords: Flexible Filamentous Particles; Heat and Mass Transfer; Experimental Model; Numerical Simulation; Rotary Dryers

Effect of calcination atmospheres on the catalytic performance of nano-CeO2 in direct synthesis of DMC from methanol and CO2 by Zixiang Cui; Jie Fan; Huijuan Duan; Junfeng Zhang; Yongqiang Xue; Yisheng Tan (29-36).
Nano-CeO2 was prepared through the calcination of Ce(OH)3 precursor in different atmospheres (H2, Ar, air, O2), which was prepared by a hydrothermal method, and then used as catalysts in the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. The results indicated that the catalyst calcined in O2 (CeO2-O2) showed an optimum catalytic performance, and the yield of DMC reached to 1.304 mmol/mmolcat. In addition, reaction temperature and weight of catalyst were optimized. Based on characterizations of the catalysts, the ratio of Ce(IV)/Ce(III) and Lewis acid-base property of nano-CeO2 catalyst could be adjusted through different calcination atmosphere treatment. It was determined that the higher activity of CeO2-O2 catalyst is mainly attributed to its higher ratio of Ce(IV)/Ce(III) as well as abundant and moderate intensity Lewis acid base sites.
Keywords: Nano-CeO2 ; Calcination Temperature; Valence State; Methanol; CO2 ; DMC

CO2 adsorption capacity of zeolite 13X and Na+-chabazite at 473 K was estimated by extrapolating the CO2 adsorption isotherm data measured in the temperature range of 298 to 373 K by employing the Clausius-Clapeyron equation, and compared with those by gravimetric measurements using a TGA unit and by the breakthrough curves obtained using a gas mixture (CO2 30% in N2 balance) in a fixed bed adsorption unit. All three methods produced comparable CO2 adsorption capacities, and justified the suggested experimental approach of the extrapolation procedure using the low temperature isotherm data for estimating gas adsorption capacity at high temperature conditions.
Keywords: Zeolites; CO2 Adsorption; Clausius-Clapeyron Equation; TGA; Breakthrough

Hierarchical porous NiO/Al2O3 composites were successfully prepared by two-steps. First, the core-shell structured Al2O3 microspheres were prepared via a template-free hydrothermal route using KAl(SO4)2·12H2O and Al2(SO4)3·18H2O as aluminum source. Then, the NiO/Al2O3 composites with micro- and nano-hierarchical structures were prepared by a hydrothermal method combining the subsequent calcination process. The obtained characterization result presented that the morphology of hierarchical Al2O3 microsphere tuned to irregular platelets by simply varying Ni/Al ratios. The BET analysis showed that the special surface area from 52.12m2 g−1 to 214.8m2 g−1 after two hydrothermal complex process. Effects of Ni/Al ratio, adsorbent dosage, Congo red (CR) concentration, coexisting ions, adsorption time and temperature were investigated. The obtained results indicated that NiO/Al2O3 composite had the high adsorption efficiency (99.6%) and great adsorption capacity (186.9mg g−1) under the optimum conditions. The adsorption isotherm and kinetics data were found to be well fitted and in good agreement with the Langmuir isotherm model and pseudo-second order model, respectively. The hierarchical porous NiO/Al2O3 composites presented remarkably higher adsorption efficiency during five recycling, which showed their potential as the highly efficient adsorbent for removal of CR in wastewater.
Keywords: NiO/Al2O3 ; Hierarchical Porous Material; Congo Red; Adsorption

Pneumatic transport characteristics of coarse size pulverized coal for the application of fast circulating fluidized bed gasification by Jin Wook Lee; Seok Woo Chung; Sang Oh Ryu; Ji Eun Lee; Yongseung Yun; Chan Lee; Yongjeon Kim; Sungkwang Lim (54-61).
The pneumatic transport characteristics of pulverized coal with very coarse grain size were investigated, especially related to fast circulating fluidized bed gasifier. The lock hopper system was used along with the top discharge blow tank technology to examine the transportation characteristics of pulverized coal. The most important factors among the pulverized coal transportation properties were mass flow rate of pulverized coal and the solid loading ratio, which changed with the amount of fluidization nitrogen and differential pressure between injection hopper and gasifier. The mass flow rate of the pulverized coal and the solid loading ratio were linearly proportional to changes in differential pressure, and were inversely proportional to changes in the amount of fluidization nitrogen. In the case of extended transport line, similar feeding characteristics were obtained by increasing the differential pressure while the level of fluidization nitrogen was kept constant. Pressure losses were observed with changes in the mass flow rate of pulverized coal, solid loading ratio, and the transport gas density in horizontal and vertical, both upward and downward, straight pipelines and at bends. Characteristics of pressure losses under various operating conditions were correlated with the nondimensional numbers such as the Reynolds number, Froude number, solid/gas density ratio, and solid loading ratio. Such correlations were reasonably consistent with the experimental results.
Keywords: Pneumatic Transport; Large Size Pulverized Coal; Fast Circulating Fluidized Bed Gasification; Froude Number; Solid Loading Ratio

Harvesting of Scenedesmus obliquus cultivated in seawater using electro-flotation by Heewon Shin; Kyochan Kim; Joo-Young Jung; Sungchul Charles Bai; Yong Keun Chang; Jong-In Han (62-65).
Seawater, when supplemented to a growth medium, appears to stimulate auto-flocculation of a certain microalgae species like Scenedesmus obliquus and thus renders its harvesting easy. To make use of this unique response for the purpose of biomass harvesting, S. obliquus was grown in a seawater-added medium and then collected in electrochemically- mediated ways. Significantly higher harvesting efficiency and energy saving were observed with electroflotation (EF) than with electro-coagulation-flotation (ECF) and the standard BG11 medium. An optimal EF condition, the highest recovery rate with least energy use, was found with a supply of 0.5 A. Seawater amendment was most beneficial in a level of 10%. All this clearly showed that applying EF to cells cultivated in the seawater-supplemented medium is a promising harvesting means that enables one to obtain algae biomass without interfering with the downstream process of biodiesel production.
Keywords: Scenedesmus obliquus ; Harvest; Seawater; Electro-flotation (EF); Electro-coagulation-flotation (ECF)

Synthesis of γ-alumina nano powder from Nepheline syenite by Mehran Chitan; Seyed Ali Hosseini; Dariush Salari; Aligholi Niaei; Habib Mehrizadeh (66-72).
Nano γ-alumina was produced using Nepheline syenite ore by leaching and precipitation process at a certain pH in the presence of sodium dodecyl sulfate (SDS) as a surfactant. The produced nanostructure was characterized by XRD, SEM, EDX, DLS, BET and FT-IR. The XRD pattern confirmed the tetragonal structure of alumina The nano structure of alumina was approved by SEM and the particle size distribution were between 41 to 486 nm, confirmed by DLS. BET analysis showed that the specific surface area of nanopowder was about 39.1 m2/g. The synthesis conditions were modeled and optimized by RSM. The optimum conditions resulted in leaching time, the mass ratio of Nepheline/HCl, and the reflux temperature of 2 h, 20, and 70 °C, respectively. Under optimum conditions, the extraction efficiency was 82%. The prepared nano γ-alumina has higher removal efficiency than commercial types in the removal of p-nitrophenol by adsorption process.
Keywords: γ-Alumina; Nanostructure; Hydrometallurgy; Nepheline Syenite; RSM; Adsorption

Photocatalytic degradation of toluene in a staged fluidized bed reactor using TiO2/silica gel by Hsiu-Po Kuo; Shang-Wen Yao; An-Ni Huang; Wan-Yi Hsu (73-80).
Relatively high concentration toluene is photocatalytically degraded in a multi-stage fluidized bed reactor continuously. The fluidizing media are titanium dioxide deposited silica gel particles, which are prepared by the doping sol-gel method. The effects of the Ti/Si atomic ratio, the inlet gas flow rates, and the number of the stages on the toluene removal efficiency were evaluated. The highest toluene removal efficiency is obtained when the fluidizing media are with the Ti/Si atomic ratio of 1.25. The apparent reaction orders are 0.4-0.5 for the single-stage system and 0.7 for the two-stage system, respectively. With an inlet toluene concentration of 1,000 ppm, a relative humidity of 30% and a volumetric flow rate of 10 L/min, the removal efficiency of toluene at the steady state is as high as 80% and is maintained in the 6-hr experimental time.
Keywords: Fluidized Bed; Multi-stage; Toluene; Photocatalytic Degradation

Effect of acid treatment of Fe-BEA zeolite on catalytic N2O conversion by Jeong Min Jeong; Ji Hye Park; Jeong Hun Baek; Ra Hyun Hwang; Sang Goo Jeon; Kwang Bok Yi (81-86).
The effect of acid treatment on the physical and chemical characteristics of BEA zeolite, as well as the catalytic activity of the Fe-BEA catalyst for N2O reduction under NH3-selective catalytic reduction (NH3-SCR) conditions, was examined. The acid treatment caused dealumination of BEA and enrichment of the silanol groups on vacant T-sites and the Brønsted acid sites. As the acid treatment time increased, the silanol groups and the weak acid sites in BEA also increased. Because the weak acid sites behave as anchoring sites for Fe ions, the catalytic activity also increased as the treatment time increased. However, extended exposure of BEA to acid decreased the catalytic activity of the Fe-BEA catalyst somewhat, and decreased the silanol groups and weak acid sites. The catalytic activity and the amount of weak acid sites were well correlated with the BEA acid treatment time.
Keywords: N2O Reduction; Fe-BEA; NH3-SCR; Acid Treatment; Dealumination

Enhancement of gasoline selectivity in combined reactor system consisting of steam reforming of methane and Fischer-Tropsch synthesis by Abbas Ghareghashi; Farhad Shahraki; Kiyanoosh Razzaghi; Sattar Ghader; Mohammad Ali Torangi (87-99).
A two-stage, one-dimensional configuration model including the steam reforming of methane (SRM) and Fischer-Tropsch (FT) synthesis has been developed for the production of hydrocarbons. This configuration is used to investigate hydrocarbon product distribution, such as gasoline. The first SRM reactor is fed by methane and steam, and the products are converted to hydrocarbons by the second FT reactor. The model was solved numerically by applying the finite difference approximation, and the set of first-order ODEs was solved in the axial direction. The results show that complete conversion of hydrogen in the second reactor can be achieved although a small amount of carbon monoxide remains. Furthermore, at higher H2O/CH4 ratio (and low CO in feed), lower C2-C5 yield and selectivity is obtained.
Keywords: Steam Reforming of Methane; Fischer Tropsch; C5 Yield; Consecutive Reactors; C5 Selectivity; CO2 Yield

Prospective application of carbon-silica derived from SiC-Si sludge as a support for Fe catalysts by Mi Sun Lee; Kyun Young Park; Hoey Kyung Park; Tae Won Kang; Hee Dong Jang; Sang Sup Han; Jong-Ki Jeon (100-104).
A unique carbon-silica (30 wt%) material was prepared by H2O activation at 700 °C for 8 h with the carbon derived from SiC-Si sludge and the in-situ hydrolysis of the SiCl4 trapped in the pores of the carbon into silica. The BET surface area of the carbon-silica was 1,750 m2/g and the pore volume by QSDFT was 1.13 cm3/g, 40% of which stemmed from micropores smaller than 2 nm with 60% from mesopores between 2 nm and 50 nm. The activated carbon-silica was loaded with Fe by means of chemical vapor infiltration (CVI) and incipient wetness impregnation (IWI). A hydrogen temperature-programmed reduction test showed that the activated carbon-silica is a prospective support material for Fe catalysts and that the dispersion of Fe in the carbon-silica is higher with CVI than with IWI.
Keywords: Carbon-silica; SiC-Si Sludge; Surface Area; Fe

Bio-solubilization of the untreated low rank coal by alkali-producing bacteria isolated from soil by Mary Grace Baylon; Yokimiko David; Sudheer D. V. N. Pamidimarri; Kei-Anne Baritugo; Cheol Gi Chae; You Jin Kim; Tae Wan Kim; Min-Sik Kim; Jeong Geol Na; Si Jae Park (105-109).
Coal is a hydrocarbon-rich fossil fuel considered as a possible replacement for petroleum as a feedstock for the production of fuel and valuable chemicals. In this study, bacteria capable of solubilizing untreated low rank coal were isolated from soil. A total of 19 microorganisms were isolated from soil enriched in MR medium with coal and were identified based on 16S rRNA sequencing. The identified soil isolates belonging to the genera Citricoccus, Comamonas, Cupriavidus, Sphingomonas, and Sphingopyxis were screened based on their growth in the chemically defined MR medium containing different concentrations of coal. Among the identified microbial strains, Cupriavidus necator S2A2, Sphingopyxis ginsengisoli S2B14 and Sphingomonas sp. S2B18 were further characterized for their ability to degrade low-rank coal. Cupriavidus necator S2A2, Sphingopyxis ginsengisoli S2B14 and Sphingomonas sp. S2B18 were found to solubilize untreated low-rank coal as indicated by the release of solubilized coal products detected at OD450 when they were grown in LB medium containing 1% coal. Sphingomonas sp. S2B18 showed the highest coal solubilization activity, based on the high absorbance of its culture supernatant (0.190). Although laccase-like activity was not detected in these strains when tested for RBBR dye degradation, increase in the pH of the culture medium up to 8.25- 8.34 was observed. This may be attributed to the excretion of alkaline substances in the culture medium. Since biosolubilization of coal by microorganisms is a good alternative for the chemical conversion of coal, microorganisms screened in this study can be potentially used as biological catalysts for the conversion of coal into valuable chemicals.
Keywords: Untreated Low-rank Coal; Coal Biosolubilization; Coal Degradation; Alkaline Degrading Substances; Low Molecular Weight Coal Products

Three kinds of solid acid catalysts were prepared from alkali lignin in the waste liquor of pulping using carbonation- sulfonation method with different pretreatment. The lignin-derived solid acids (LDSAs) were characterized by FESEM, XRD, FTIR, TGA, BET and acid-base titration, respectively. A comparison study on the catalytic performance of LDSA prepared by different pretreatment method before carbonation in the hydrolysis of microcrystalline cellulose (MCC) was carried out. Results showed that the LDSA prepared by chemical activation with phosphoric acid (LPC-SO3H) exhibited superior catalytic activity due to its higher densities of -COOH group (1.68 mmol/g) as binding site and -SO3H group (0.88 mmol/g) as catalytic site as well as its larger specific surface area (488.4 m2/g) than those of the other two LDSAs. A total reducing sugar yield of 50.8% in MCC hydrolysis was obtained under the reaction conditions of temperature of 180 °C, time of 3 h, MCC concentration of 6 mg/mL and mass ratio of catalyst to MCC of 3.3 (w/w). Additionally, the value activation energy for hydrolysis of MCC to reducing sugars using LPC-SO3H was 83.31 kJ/mol, which was smaller than that using sulfuric acid.
Keywords: Lignin; Carbon-based Solid Acid; Catalyst; Cellulose Hydrolysis

Bacterial L-asparaginase has been widely used as a potential therapeutic agent in the treatment of various lymphoblastic leukemia diseases. We studied product and dual substrates utilization kinetics by P. carotovorum MTCC 1428 in batch bioreactor. The kinetic study revealed that the maximum growth of P. carotovorum MTCC 1428 was achieved at 2 g l −1 and 5 g l −1 of glucose and L-asparagine, respectively. Different substrate inhibition models were fitted to the growth kinetic data and the additive form of double Luong model was found to best explain the growth kinetics of P. carotovorum MTCC 1428. The kinetic parameters of growth studies showed that the predicted maximum inhibition concentration of glucose (S mg ) and L-asparagine (S ma ) was close to the experimentally observed value 15.0 and 10 g l −1, respectively. Modified form of the Luedeking-Piret model was used to describe the kinetics of L-asparaginase production, and the system seems to be mixed growth associated. Kinetic models of dual substrate growth, L-asparaginase production and substrate(s) utilization by P. carotovorum MTCC 1428 well fitted with experimental data with regression coefficients (R2) value of 0.97, 0.96 and 0.93, respectively.
Keywords: Anti-leukemic Enzyme; L-asparaginase; Pectobacterium carotovorum ; Growth Kinetics; Multiple-substrate; Production Kinetics

Extraction of bioethanol from fermented sweet sorghum bagasse by batch distillation by Guangming Li; Jihong Li; Shizhong Li; Xu Zu; Lei Zhang; Lisong Qi; Weiliang Xu (127-132).
Extraction of bioethanol, a potential alternative to fossil fuel in the transport industry, from sweet sorghum stems [Sorghum bicolor (L.) Moench] using solid-state fermentation (SSF) technology has become a popular research topic worldwide. Because SSF technology can directly convert fermentable sugars into target products without juice squeezing and water input, this method can potentially reduce energy and water consumption. However, ethanol extraction from fermented sweet sorghum bagasse requires further investigation. We used batch solid-state distillation to investigate the optimal operating parameters in a distillation column (diameter, 400 mm) via a single-factor experiment. Results showed that the optimal steam flow rate and loading height were 8-10 kg·h−1 and 700-1,000 mm, respectively. Under optimal conditions, an energy consumption of 3.82 tons of steam per ton of ethanol and distillate concentration of 60.9% (v/v) were obtained. The pseudo-first-order rate equation was used to describe the distillation kinetics, and good correlations were obtained. Therefore, solid-state distillation can be effectively used to extract ethanol from fermented sweet sorghum bagasse.
Keywords: Ethanol Extraction; Sweet Sorghum Bagasse; Batch Solid-state Distillation; Condition Optimizing; Pseudo-first-order Rate Equation

Dissolving microneedles are transdermal delivery systems designed to mechanically penetrate the skin and fully dissolve in the skin in a minimally invasive manner. In this study, the skin permeability of compounds encapsulated in microneedles was controlled by changing the composition of microneedle materials. Sodium hyaluronate (SH) and carboxymethyl cellulose (CMC) were chosen as structural materials and amylopectin was used to increase the mechanical strength of microneedles. To determine the effect of microneedle composition on skin permeability, microneedle properties such as mechanical strength and solubility were investigated according to various compositions of SH and CMC. When the CMC fraction in the needle increased, the mechanical strength of the microneedle increased, leading to high skin permeability of rhodamine B, a model compound. Using microneedles, significantly higher skin permeability of niacinamide was also obtained. These results indicate that the microneedles developed in this study improved the skin permeability of compounds loaded in the needle, and the skin permeability could be tuned by changing the composition of microneedle materials.
Keywords: Dissolving Microneedles; Microneedle Composition; Skin Permeability; Sodium Hyaluronate; Carboxymethyl Cellulose

Algicidal effects of thiazolinedione derivatives against Microcystis aeruginosa by Don-Sang You; Yeon Woong Lee; Dubok Choi; Young-Cheol Chang; Hoon Cho (139-149).
Novel algicidal compounds against Microcystis aeruginosa were developed. A series of 64 thiazolidinedione (TD) derivatives were synthesized and analyzed for algicidal activity. Eleven compounds (2, 22, 38, 40, 49, 52, 54, 56, 58, 60, and 63) showed potent specific algicidal activity against M. aeruginosa with IC50 values <0.5 μM. An acute ecotoxicity test for these compounds was conducted using Danio rerio for ten days to verify their environmental impacts. Compounds 2 and 22 presented low ecotoxicity (EC50 13.59 and 8.59 μM, respectively). To evaluate the ecotoxic effect of various concentrations of compound 2, Daphnia magna were treated with 2.0, 2.3, 2.7, or 3.0 μM compound 2 for 25 days. Survival rate was 100% after 25 days in the 2.0 μM group, but declined to 96% at 8 days and 30% at 17 days in the 2.3 μM group. Our results indicate that compound 2 could be a potential bio-agent for controlling harmful algal blooms.
Keywords: Thiazolidinedione; Algicidal Activity; Microcystis aeruginosa ; Ecotoxicity

In order to better understand the hydrodynamics of valve trays, air-water operation in an industrial scale tower with 1.2 m of diameter, consisting of two 14% valve trays, was studied. Experimental results of clear liquid height, froth height, average liquid holdup, dry pressure drop, total pressure drop, weeping and entrainment were investigated, and empirical correlations were presented. Then, a three-dimensional computational fluid dynamics (CFD) simulation in an Eulerian framework for valve tray with ANSYS CFX software was done. The drag coefficient, which was used in the CFD simulations, was calculated from the data obtained in the experiments. The simulation results were found to be in good agreement with experimental data at this industrial scale. The objective of the work was to study the extent to which experimental and CFD simulations must be used together as a prediction and design tool for industrial trays.
Keywords: Valve Tray; Computational Fluid Dynamics; Weeping; Entrainment; Clear Liquid Height

Porous polyethersulfone hollow fiber membrane in CO2 separation process via membrane contactor - The effect of nonsolvent additives by Gholamreza Bakeri; Masoud Rezaei-DashtArzhandi; Ahmad Fauzi Ismail; Takeshi Matsuura; Mohd Sohaimi Abdullah; Ng Be Cheer (160-169).
A membrane contactor (MC) is used for natural gas sweetening and wastewater treatment with a membrane that is acting as a separating barrier between two phases, usually liquid and gas. The performance of membrane is governed by parameters such as pore size, porosity, tortuosity and surface hydrophobicity, which can be controlled by a number of methods. Addition of nonsolvents to spinning solution is known to be one of such methods. In this study, the effects of low molecular weight additives as phase inversion promoters on the morphology of polyethersulfone hollow fiber membranes and their performance in gas-liquid MC processes were investigated. It was found that among the six nonsolvent additives under study, addition of water resulted in the highest CO2 flux, by decreasing the thermodynamic stability of polymer solution and maintaining high solvent-nonsolvent exchange rate.
Keywords: Polyethersulfone; Membrane Contactor; Phase Inversion Promoter; Hollow Fiber Membrane

A three-dimensional neural network model has been designed for representing the phase equilibrium data related to aqueous two-phase systems. The polyvinyl pyrrolidone/phosphate/water system was selected as the model system to demonstrate the point of interest. The collected experimental data were categorized into two subsets, training and validation sets, not only to find the suitable network configuration but also to prevent the overfitting problem. Meanwhile, the weight comparison method was proposed to optimize the three-dimensional neural net. The results of accuracy comparison indicate that it outperforms the two-dimensional neural network on some details and can further enhance the calculation accuracy of the phase equilibrium data for these investigated aqueous two-phase systems. The development of the neural network in the three-dimensional space should be a research project of concern.
Keywords: Three-dimensional Neural Network; Weight Comparison Method; Aqueous Two-Phase System; Phase Equilibria

Fluoride contamination of water is a potential health and environmental hazard worldwide. This study focuses on defluoridation efficiency in aqueous system by novel adsorbents, i.e., calcium impregnated silica (Ca-SiO2) and calcium impregnated silica combined with titanium dioxide (Ca-SiO2-TiO2). Comparative batch study was carried out using both adsorbents Ca-SiO2 and Ca-SiO2-TiO2 for fluoride removal efficiency in different experimental conditions where it was observed that chemically modified Ca-SiO2-TiO2 acted as a better adsorbent for defluoridation than Ca-SiO2. Thus, further batch isotherm and kinetics studies were performed using Ca-SiO2-TiO2. The phenomenon of fluoride ion uptake is realized by Langmuir and Freundlich isotherm model. Langmuir isotherm shows satisfactory fit to the experimental data. The rate of adsorption shows that the pseudo-second-order rate fitted the adsorption kinetics better than the pseudo-first-order rate equation. The mechanism of adsorption process was illustrated by calculating Gibbs free energy, enthalpy and entropy from thermodynamic studies. To further confirm the applicability of the adsorbent, a fixed bed study was carried out in column mode. Thomas and bed-depth-service-time (BDST) model were well-fitted to the experimental results. The optimal operating conditions of defluoridation were found by using response surface methodology (RSM) with the help of Design Expert Software. The maximum percentage of fluoride removal was 92.41% in case of calcium impregnated silica combined with titanium dioxide (Ca-SiO2-TiO2). Thus, it may be concluded that chemically synthesized Ca-SiO2-TiO2 could be used as an environmentally and economically safe adsorbent for defluoridation of waste water.
Keywords: Defluoridation; Ca-SiO2-TiO2 ; Response Surface Methodology; Fixed-bed Adsorption Study; Langmuir Isotherm Model

The effect of a magnetic field on the early stages of Soret-driven convection of a nanoparticle suspension with large negative separation ratio χ confined within a Hele-Shaw cell, heated from above, was analyzed. Taking the Lorentz force into account, new stability equations were formulated in a similar (τ, ζ)-domain as well as in a global (τ, z)-domain by introducing the Hele-Shaw Rayleigh number based on the Soret flux (RsH) and the Hele-Shaw Hartmann number (Ha H ). With and without the quasi-steadiness assumptions, the resulting stability equations were solved analytically by expanding the disturbances as a series of orthogonal functions, and also the numerical shooting method was used. The critical time of the onset of convection and the corresponding wave number were obtained as a function of Rs H and Ha H . It was found that the magnetic field plays a critical role in the onset of convective instability. The onset time increases with increasing Ha H and decreasing RsH. The linear stability limits are independent of the solution methods, if the trial functions for the disturbance quantities are properly chosen. Based on the results of the linear stability analysis, a non-linear analysis was conducted using direct numerical simulations. The non-linear analysis revealed that the convective motion can be apparent far after the linear stability limit.
Keywords: Soret-driven Convection; Nanoparticle Suspension; Magnetic Field Effect; Hele-shaw Cell; Linear Stability Analysis; Non-linear Analysis

A one-dimensional reactor model was employed to perform parametric studies for CO2 reforming of methane in a membrane reactor to investigate its feasibility as a new CO2 utilization process. The effect of key variables such as hydrogen permeance and Ar sweep gas flow rate to facilitate H2 transport from a shell side (retentate) to a tube side (permeate) on the performance in a membrane reactor was studied at various temperatures with numerical simulation validated by experimental results. In addition, increase in CH4 conversion and H2 yield enhancement observed in membrane reactor was successfully confirmed by profiles of H2 partial pressure difference between shell and tube sides. From the numerical simulation studies, the feasibility of using a membrane reactor for CO2 reforming of methane was confirmed by increased CH4 conversion and H2 yield enhancement compared to a packed-bed reactor at the same condition, which in turn leads to significant cost reductions due to a reduced operating temperature. Moreover, a window of H2 permeance and a guideline for Ar sweep gas flow rate for the efficient membrane reactor design was obtained from this study.
Keywords: CO2 Utilization; CO2 Reforming; Membrane Reactor; Hydrogen Permeance; Numerical Simulation

The solubility of hexaquoiron(III)tris(p-toluenesulfonate) [Fe(OTs)3·6H2O] in (ethanol+water) mixtures with a mole fraction of 0–0.327 ethanol was measured from 291.15 to 333.15 K by using a synthetic method. The experimental results show that the solubility of Fe(OTs)3·6H2O increases with an increase in temperature and an enrichment in ethanol content. The solubility data were correlated by the modified Apelblat equation, the Redlich-Kister (CNIBS/R-K) model, and the hybrid model, and the results showed that the three models agree well with experimental data. The thermodynamic properties of the dissolution process, including enthalpy, entropy, and Gibbs energy were estimated from the experimental data by the modified van’t Hoff equation, indicating that the process of the dissolution of Fe(OTs)3·6H2O is endothermic and spontaneous.
Keywords: Hexaquoiron(III)tris(p-toluenesulfonate); Thermodynamics; Correlation; Solubility; Phase Equilibria

The density, refractive index, and kinematic viscosity were measured for extraction solvents for molybdenum: methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), trihexyl tetradecyl phosphonium chloride ([P666,14] [Cl]), trihexyl tetradecyl phosphonium dicyanamide ([P666,14][DCA]) and trihexyl tetradecyl phosphonium bis (2,2,4- trimethyl pentyl) phosphinate ([P666,14][TMPP]) at atmospheric pressure for a temperature range of 288.15-318.15 K. The experimental data were correlated using the Daubert and Danner equation, a linear equation and the Goletz and Tassion equation. In addition, the excess molar volumes (VE) and the deviations in molar refractivity (ΔR) at 298.15 K were reported for the following binary systems: {MEK+[P666,14][Cl]}, {MEK+[P666,14][DCA]}, {MEK+[P666,14][TMPP]}, {MIPK+[P666,14][Cl]}, {MIPK+[P666,14][DCA]} and {MIPK+[P666,14][TMPP]}. The determined VE and ΔR values were correlated with the Redlich-Kister equation. The binary density and refractive index data at 298.15 K were also predicted using several mixing rules, and these results were then compared with the experimental data.
Keywords: Density; Refractive Index; Kinetic Viscosity; Excess Property; Deviation Property

Synthesis of aragonite-precipitated calcium carbonate from oyster shell waste via a carbonation process and its applications by Chilakala Ramakrishna; Thriveni Thenepalli; Choon Han; Ji-Whan Ahn (225-230).
Oyster shells are abundantly available in nature without eminent use and are dumped into landfills in vast quantities. Their improper disposal causes environmental problems, resulting in a waste of natural resources. Recycling shell waste could potentially eliminate the environmental problems and, moreover, convert the waste into high-valueadded products, such as synthetic precipitated calcium carbonate (PCC), which can be obtained from oyster waste and which is used to enhance the mechanical properties of various materials. It can also be used as a filler material in the plastic and paper industries. This study presents a simple method for the extraction of aragonite needles from oyster shell waste via a carbonation process. The obtained aragonite-precipitated calcium carbonate (PCC) is characterized by XRD and SEM, which is used to assess the morphology and particle size. Using the proposed process, oyster shell waste powder was calcined at 1,000 °C for 2 h, after which the calcined shell powder was dissolved in water for hydration. The hydrated solution was mixed with an aqueous solution of magnesium chloride at 80 °C and CO2 was then bubbled into the suspension for 3 h to produce needle-shaped aragonite PCC. Finally, aragonite-type precipitated calcium carbonate was synthesized from the oyster shell powder via a simple carbonation process, yielding a product with an average particle size of 30-40 μm.
Keywords: Oyster Shell Waste; Calcium Carbonate; Aragonite PCC; Mineral Filler

Aqueous-phase synthesis of metal nanoparticles using phosphates as stabilizers by Inho Kim; Soo-Hong Lee; Byungkwon Lim; Bum Jun Park; Suk Ho Bhang; Taekyung Yu (231-233).
We describe a simple, aqueous-phase route to the synthesis of metal nanoparticles including Pt, Pd, Ru, and Au based on the aqueous-phase reduction of metal salts with NaBH4. In this approach, various phosphates were applied as new type of stabilizers for the synthesis of metal nanoparticles thanks to its negatively charged functional group (PO).
Keywords: Nanoparticle; Platinum; Palladium; Ruthenium; Phosphate

The ability of nano-ZrO2 and modified nano-ZrO2 with humic acid (ZrO2-H) to remove Cd2+, Cu2+ and Ni2+ from aqueous media has been tested by batch sorption studies varying the contact time, initial metal concentration, initial solution pH, sorbent dosage and temperature to understand the adsorption behavior of these metals through adsorption kinetics and isotherms. The bare nanoparticles (NPs) and modified NPs (MNPs) were characterized using X-ray powder diffraction (XRD), SEM-EDX, FTIR to determine the phase, average grain size, morphology, surfacial elemental compounds and functional groups of NPs and MNPs. The pH of the solutions and the temperature controlled the adsorption of metal ions by NPs and MNPs as well as maximum uptake occurred in the first 120min of reaction in almost all metals. The kinetics of adsorption followed a pseudo-second-order rate equation (R2>0.97) and the isotherms were well described by the Freundlich model in Cd2+ and Cu2+, but in Ni2+ isotherms were better described by Langmuir model. The adsorption of metals onto almost all NPs and MNPs were spontaneous and endothermic in nature. Among the three metals, Cd2+ showed more preference towards the sites on ZrO2 and ZrO2-H than Cu2+ and Ni2+. This study reveals that ZrO2 and ZrO2-H are effective adsorbents in removing Cd2+, Cu2+ and Ni2+ from the aqueous environment with an adsorptive capacity of 46.2, 59.7, 39.5, 29.7, 9.2 and 16.7mg·g−1, respectively.
Keywords: ZrO2 Nanoparticles; Heavy Metals; Water; Sorbent

Heat dissipation during operations of electronic devices is a serious issue with device miniaturization and high power consumption. As one practical approach to reducing the device temperature, thermally conductive adhesives can be used between printed circuit board and heatsink materials. By incorporating the aluminum nitride (AlN) with acrylic copolymer matrix, thermal conductivity and adhesive properties are examined with different sizes and content of particulate fillers. Acrylic copolymer is synthesized using butyl acrylate and acrylic acid monomers via solution polymerization, and AlN particles are used as thermally conductive fillers. The overall monomer conversion reaches more than 96% after 140 min reaction time. Considering both adhesive properties and thermal conductivity of adhesives, it is desirable to apply 20 wt% nano-AlN filler to acrylic copolymer adhesives.
Keywords: Thermal Conductivity; Adhesive; Adhesion; Polymers; Composites

Esterification of propionic acid with isopropyl alcohol over ion exchange resins: Optimization and kinetics by Vishal Suresh Chandane; Ajit Pralhad Rathod; Kailas Lachchhuram Wasewar; Shriram Shaligram Sonawane (249-258).
The esterification of propionic acid with isopropyl alcohol was studied in an isothermal batch reactor. The activities of three different types of ion exchange resin catalysts (Amberlyst 15, Amberlyst 70 and Dowex 50 WX8) were investigated, and Amberlyst 15 was found to be an effective catalyst for the reaction. The effects of process parameters, namely, catalyst loading, alcohol to acid molar ratio and reaction temperature, were studied and optimized. Response surface methodology (RSM) was applied to optimize the process parameters as well as to investigate the interaction between process parameters. The internal and external diffusion limitations were found to be absent at a stirring speed of 500 rpm. The RSM model predicted response (83.26%) was verified experimentally with a good agreement of experimental value (83.62±0.39%). Moreover, the kinetics was studied and the Langmuir-Hinshelwood model was used to fit the kinetic data.
Keywords: Ion Exchange Resin; Amberlyst 15; Dowex 50 WX8; Response Surface Methodology; Box-Behnken Design

High performance methyl orange capture on magnetic nanoporous MCM-41 prepared by incipient wetness impregnation method by Talib Mohammed Albayati; Ghanim Magbol Alwan; Omar Sabah Mahdy (259-265).
The Magnetic nanoporous material Fe/MCM-41 was prepared, and its physical characterization studied, to determine the effect of its properties on separation efficiency of methyl orange (MO) from wastewater by adsorption process. The experimental results were analyzed for both adsorbent mesoporous material samples, MCM-41 and magnetic Fe/MCM-41, in order to select the best operating conditions for the different studied parameters, which are: constant temperature (20 °C), pH: (2) adsorbent dosage (0.03 gm), contact time (10minute) and concentrations (30mg/L). The results demonstrate that the adsorption processes can be well fitted by the Langmuir isotherm model for pure MCM-41, with a correlation coefficient of (0.999), and fitted by the Freundlich isotherm model for magnetic Fe/ MCM-41, with a correlation coefficient of (0.994). The adsorption kinetics of MO on to MCM-41 and Fe/MCM-41 are well described by a pseudo-second-order kinetic model.
Keywords: Separation; Wastewater; MCM-41; Methyl Orange; Adsorption

Electroless Pd deposition on a planar porous stainless steel substrate using newly developed plating rig and agitating water bath by Beom-Seok Seo; Jae-Yun Han; Kwan-Young Lee; Dong-Won Kim; Shin-Kun Ryi (266-272).
A new plating bath was developed to prevent palladium plating in the pores of the porous stainless steel support when using plate-type porous substrate. The plating bath, composed of a holder, a rubber O-ring and a bottom, provides very simple assembly and is very effective in preventing palladium plating in the pores of porous stainless steel. The agitation of the plating solution increases plating rate significantly because the agitation improves the external mass transfer of Pd ion and reducing agent to the membrane surface facilitating ~99.7% plating yield of palladium ion. This new plating method carried out at a temperature range of 293 to 298 K provides a very simple and economic membrane manufacturing process. Using a newly developed plating rig, an 88.9-mm diameter membrane was fabricated, and gas permeation tests showed that the hydrogen permeation flux reached ~0.9 mol s−1 m−2 at 873 K and a pressure difference of 300 kPa and selectivity (H2/N2) was ~1,850 at 873 K with a pressure difference of 100 kPa.
Keywords: Pd Membrane; Hydrogen; Electroless Plating; Porous Stainless Steel; External Mass Transfer