Korean Journal of Chemical Engineering (v.29, #10)
One-step synthesis of mesoporous sulfated zirconia nanoparticles with anionic template by Hongping Pu; Liuyi Zhang; Dongquan Du; Caiyun Han; Hongyin Li; Jiangyan Li; Yongming Luo (1285-1288).
Mesoporous sulfated zirconia nanoparticles (MSZNP) with high surface area have been synthesized by using sodium dodecyl sulfate (C12H25OSO3Na, SDS), both as a template and a sulfating agent via one-step route. On the basis of FT-IR, EDS together with NH3-TPD analyses, the SO 4 2− anion, originated from the hydrophilic head of SDS, can be incorporated into ZrO2 to form MSZNP with super-acidity. The phase transition of ZrO2 from tetragonal to monoclinic phase was effectively inhibited by the presence of SO 4 2− , and the formation mechanism was illustrated in detail. MSZNP(550) achieved far higher activity than CSZ(550) in transesterification of soybean oil with methanol due to the synergistic effect of strong acidity, high BET surface area and the formation of mesostructure.
Keywords: Sulfated Zirconia; Nanoparticles; Porous Materials; One-step Route; Transesterification
Vegetable oil aided hydrothermal synthesis of cerium oxide nanocrystals by Minsoo Kim; Hong-shik Lee; Young Ho Shin; Ki Ho Ahn; Yong-Suk Youn; Jaehoon Kim; Youn-Woo Lee (1289-1291).
Hydrothermal synthesis of cerium oxide nanocrystals was performed with in-situ surface modification using soybean oil and palm oil as capping agents. The synthesized nanocrystals were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). TEM results showed single crystalline nature with stable dispersion. FT-IR spectra and TGA plots further confirmed the adsorption of fatty acid molecules onto cerium oxide surface. Our findings have the advantages of reduced materials costs compared to using single component surfactants and the production of valuable by-product glycerol.
Keywords: Hydrothermal Synthesis; Supercritical Water; Surface Modification; Cerium Oxide; Vegetable Oil
Isothermal and non-isothermal kinetic and safety parameter evaluation of tert-butyl(2-ethylhexyl)monoperoxy carbonate by differential scanning calorimetry by Lu-Yen Chen; Chung-Hwei Su; Kuen-Yuan Chuang; Chun-Ping Lin; Shuh-Woei Yu; Jo-Ming Tseng (1292-1297).
Tert-butyl(2-ethylhexyl)monoperoxy carbonate (TBEHC) 95 mass% is intrinsically a very unstable substance that can induce self-decomposition even under normal atmospheric condition. During storage, TBEHC 95mass% can release an enormous amount of heat if the temperature is higher than the recommended storage temperature, due to the self-accelerating reaction having been ignited. In this study, TBEHC 95mass% was tested by differential scanning calorimetry (DSC) under five heating rates (1, 2, 4, 6, and 8 °C/min) and four isothermal conditions (120, 125, 130, and 135 °C) to evaluate the basic kinetic and safety parameters of time to maximum rate (TMR), self-accelerating decomposition temperature (SADT), and temperature of no return (TNR). Under runaway reaction TBEHC 95 mass% releases a great quantity of heat. This study establishes an important guiding principle for related manufacturing processes worldwide.
Keywords: Tert-butyl(2-ethylhexyl)monoperoxy Carbonate (TBEHC); Differential Scanning Calorimetry (DSC); Kinetic and Safety Parameters; Runaway Reaction
A hybrid optimization strategy for simultaneous synthesis of heat exchanger network by Zhaoyi Huo; Liang Zhao; Hongchao Yin; Jianxiong Ye (1298-1309).
The heat exchanger network synthesis problem often leads to large-scale non-convex mixed integer nonlinear programming formulations that contain many discrete and continuous variables, as well as nonlinear objective function or nonlinear constraints. In this paper, a novel method consisting of genetic algorithm and particle swarm optimization algorithm is proposed for simultaneous synthesis problem of heat exchanger networks. The simultaneous synthesis problem is solved in the following two levels: in the upper level, the network structures are generated randomly and reproduced using genetic algorithm; and in the lower level, heat load of units and stream-split heat flows are optimized through particle swarm optimization algorithm. The proposed approach is tested on four benchmark problems, and the obtained solutions are compared with those published in previous literature. The results of this study prove that the presented method is effective in obtaining the approximate optimal network with minimum total annual cost as performance index.
Keywords: Heat Exchanger Network Synthesis; Discrete and Continuous Variables; Genetic Algorithm; Particle Swarm Optimization
Reduction of thermal radiation by steam in flare stack system by Heon Seok Lee; Byung Seok Ko; Jae Mo Yang; Chang Jun Lee; Jin Hwan Yoo; Dongil Shin; Chulhwan Park; Jae Wook Ko (1310-1320).
A flare system is installed for the enhancement of process safety, and the stable combustion is one of the most important elements. The main function of the flare system is the combustion of the flammable or toxic materials into non-hazardous materials, but combustion heat is released from a flare system. In this study, the effect of the external and internal steam injections in the flare stack on the reduction of the thermal radiation was investigated. The ignition possibility by the change of steam amount and the effect of the steam on the thermal radiation were also analyzed by using consequence analysis software. In case of thermal emission of oil refinery plants through improved steam injection, the injection of 120% steam rather than the conventional method enabled the reduction of the flare stack height. It could reduce the height of flare stack by 20%.
Keywords: Flare Stack; Thermal Radiation; API 521; Steam; Jet Fire
Convective heat transfer of alumina nanofluids in laminar flows through a pipe at the thermal entrance regime by Seokwon Kim; Hansol Yoo; Chongyoup Kim (1321-1328).
The convective heat transfer characteristics of aqueous alumina nanofluids were investigated experimentally under forced laminar tube flows. The particles had different shapes of cylinders, bricks and blades, and particle loading was between 0–5 volume%. The nanofluids were characterized rheologically, and the heat transfer system was validated by using water without particles. In calculating Nusselt and Peclet numbers to assess heat transfer enhancement of nanofluids, physical properties of water were used so as not to exaggerate the amount of heat transfer. It was found that heat transfer coefficients of nanofluids are almost the same or a little smaller than that of water. The heat transfer coefficient can be reduced by the lowering the thermal conductivity of the nanofluid under shearing conditions and particle depletion by the cluster migration from the wall to the tube center. The reduction in thermophysical properties also contributes to the reduction in heat transfer coefficient. It has been concluded that nanofluids from metal particles with appropriate stabilizing agents can satisfy the requirements to be a practically usable nanofluid.
Keywords: Leveque Problem; Dispersion; Gel; Migration; Thermal Conductivity
Carbon dioxide reforming of methane to synthesis gas over LaNi1−x Cr x O3 perovskite catalysts by Joonho Kim; Taeyoon Kim; Jung Whan Yoo; Ki Bong Lee; Suk-In Hong (1329-1335).
Carbon dioxide reforming of methane was investigated over LaNi1−x Cr x O3 perovskite catalysts which were prepared by the malic acid method. The respective perovskite catalysts were a single phase of perovskite oxide without impurity phases. Their reduction behavior was characterized by temperature programmed reduction. In the LaNi1−x Cr x O3 perovskite catalysts, the catalytic activities were closely related to the reduction behavior of the catalysts, and the partial substitution of Cr to the B-site of perovskite catalysts promoted stability against reduction. When the x values were lower than 0.4, the LaNi1−x Cr x O3 perovskite catalysts were decomposed to La2O3 and Ni and the decomposition of perovskite structure led to large coke deposition. When the x values were higher than 0.4, the LaNi1−x Cr x O3 perovskite catalysts showed reduced catalytic activity but became stable to reduction and coke formation in the reforming reaction.
Keywords: CO2 Reforming; Methane; Perovskite; Synthesis Gas
A study on thermal analysis of MgH2 powder made by hydriding chemical vapor deposition method by Kyungduck Park; Jeongseb Han (1336-1340).
The desorption kinetics of Mg hydride made by the HCVD method was assessed by thermal analysis in order to study desorption behavior. Desorption kinetics was analyzed by the theoretical equation which was derived on the basis of a continuous moving boundary model. At various initial hydride wt% from 1.65 to 7.42, the sample was heated to 573 K at a rate of 1.0 K/min. The starting temperature of evolution of hydrogen rises higher as the initial hydride wt% increases. The number of thermal desorption peaks corresponds to the occupation sites of hydrogen. As the heating rate was increased, the peak temperatures increased; the peak temperatures for heating rates 1, 2, 3 and 4 K/min were 667, 683, 690 and 698 K, respectively. The pressure range is 0.1 to 0.2 atm for measuring. The activation energy for the decomposition of Mg hydride made by HCVD method was 166 kJ/ mol.
Keywords: Hydrogen Storage; HCVD; Thermal Desorption
Comparison of bioethanol production of simultaneous saccharification & fermentation and separation hydrolysis & fermentation from cellulose-rich barley straw by Kyung Yoen Won; Young Soo Kim; Kyeong Keun Oh (1341-1346).
Cellulose rich barley straw, which has a glucan content of 62.5%, followed by dilute acid pretreatment, was converted to bioethanol by simultaneous saccharification and fermentation (SSF). The optimum fractionation conditions for barley straw were an acid concentration of 1% (w/v), a reaction temperature of 158 °C and a reaction time of 15 min. The maximum saccharification of glucan in the fractionated barley straw was 70.8% in 72 h at 60 FPU/gglucan, while the maximum digestibility of the untreated straw was only 18.9%. With 6% content WIS (water insoluble solid) for the fractionated barley straw, 70.5 and 83.2% of the saccharification yield were in SHF and SSF (representing with glucose equivalent), respectively, and a final ethanol concentration of 18.46 g/L was obtained under the optimized SSF conditions: 34 °C with 15 FPU/g-glucan enzyme loading and 1 g dry yeast cells/L. The results demonstrate that the SSF process is more effective than SHF for bioethanol production by around 18%.
Keywords: Barley Straw; Bioethanol; Fractionation; Simultaneous Saccharification Fermentation (SSF); Pretreatment
Comparative study on the effect of various pretreatment methods on the enrichment of hydrogen producing bacteria in anaerobic granulated sludge from brewery wastewater by Parviz Mohammadi; Shaliza Ibrahim; Mohamad Suffian Mohamad Annuar (1347-1351).
Five pretreatment methods, namely chemical, acid, heat-shock, freezing and thawing, and base, were evaluated for the enrichment of hydrogen-producing bacteria in anaerobic granulated sludge, which will be subsequently used as seed in biological hydrogen production. All the pretreatments showed positive effects towards improving hydrogen (H2) generation by the microbial population with higher hydrogen production yield and COD removal efficiency as compared to control. The granulated sludge pretreated by heat-shock showed maximum accumulated H2 (19.48mLg−1-COD), COD removal efficiency (62%), and biomass concentration (22.5 gL−1).
Keywords: Biohydrogen Production; Enrichment; Granulated Sludge
Comparison of different fluid dynamics in activated sludge system for the treatment of a stimulated milk processing wastewater: Process analysis and optimization by Ali Akbar Zinatizadeh Lorestani; Hojjatollah Bashiri; Azar Asadi; Hossein Bonakdari (1352-1361).
Wastewater from the milk industry usually undergoes activated sludge ahead of refining treatments, final discharge or reuse. To identify the most effective bioreactor hydraulic regime for the secondary treatment of wastewater resulting from the milk industry in an activated sludge system, two lab-scale activated sludge systems characterized by a different configuration and fluid dynamics (i.e., a compartmentalized activated sludge (CAS) with plug flow regime and a complete mixed activated sludge (AS)) were operated in parallel, inoculated with the same microbial consortium and fed with identical streams of a stimulated dairy wastewater. The effect of three process and operational variables—influent chemical oxygen demand (COD) concentration, sludge recycle ratio (R) and hydraulic retention time (HRT)—on the performance of the two systems were investigated. Experiments were conducted based on a central composite face-centered design (CCFD) and analyzed using response surface methodology (RSM). The region of exploration for treatment of the synthetic wastewater was taken as the area enclosed by the COD in (200, 1,000 mg/l), R (1, 5), and HRT (2, 5 h) boundaries. To evaluate the process, three parameters, COD removal efficiency (E), specific substrate utilization rate (U), and sludge volume index (SVI), were measured and calculated over the course of the experiments as the process responses. The change of the flow regime from complete-mix to plug flow resulted in considerable improvements in the COD removal efficiency of milk wastewater and sludge settling properties. SVI levels for CAS system (30–58 ml/g) were considerably smaller that for the AS system (50–145 ml/g). In addition, the biomass production yield could be reduced by about 10% compared to the AS system. The results indicated that for the wastewater, the design HRT of a CAS reactor could be shortened to 2–4 h.
Keywords: Compartmentalized Activated Sludge (CAS) System; Process and Operational Factors; Milk Wastewater
Immobilization of heavy metals in a contaminated soil using organic sludge char and other binders by Feng Li; Rabindra Bade; Sanghwa Oh; Won Sik Shin (1362-1372).
The applicability of tannery (TSC) and dye sludge char (DSC) as a binder to immobilize heavy metals (Zn, Cu and Ni) in soil was investigated. The toxicity characteristic leaching procedure (TCLP) was used to estimate the immobilization efficiency for single-binders (TSC and DSC) and binary-binders (TSC or DSC combined with tripostassium phosphate (K3PO4) diammonium phosphate (DAP), lime or ladle slag). The immobilization efficiencies of Zn, Cu and Ni by TSC amendment were 84.2, 100.0 and 40.0%, respectively, which were higher than 28.5, 100.0 and 54.9% by DSC amendment for a binder dose of 0.80 g char/g soil. The binary-binder enhanced Zn immobilization to 56.3 and 97.2% at 0.6 g-DSC/0.06 g-Ca(OH)2 and 0.4 g-TSC/0.08 g-Ca(OH)2, respectively per 1 g dried soil. The immobilization efficiencies of heavy metals increased with aging for the DSC-binary binders, but not for TSC-binary binders.
Keywords: Char; Dye Sludge; Heavy Metals; Immobilization; Tannery Sludge
A dynamic adsorption model for the gas-phase biofilters treating ethanol: Prediction and validation by Eun Ju Lee; Kwang-Hee Lim (1373-1381).
A dynamic adsorption model was proposed using the lumping process for an adsorption system. This novel approach uses a four-component structure model: gas phase, enclosed aqueous phase, sorption volume and porous media surface adsorption. A clouding effect represented by k a (dynamic adsorption constant) was adopted to explain the adsorption process. The clouding effect assumes that the adsorption rate is decreased as the adsorption sites on the media surface are occupied. In the equilibrium stage the Freundlich adsorption isotherm was adopted. The proposed dynamic adsorption model was then predicted in comparison with the experimental data of an adsorption-column to estimate adsorption model parameter values in a biofilter fed with ethanol at 4,100 mg ethanol/m3 (or 2,000 ppmv). Model validation was performed for the adsorption column fed with ethanol at 2,050 mg ethanol/m3 (or 1,000 ppmv). Results showed that the mechanistic model was able to simulate the dynamic behavior of an adsorption process successfully according to the corresponding adsorption experimental data.
Keywords: Dynamic Adsorption Model; Process Lumping; VOC; Model Prediction
Boron removal by means of chemical precipitation with calcium hydroxide and calcium borate formation by Alper Erdem Yilmaz; Recep Boncukcuoğlu; Serkan Bayar; Baybars Ali Fil; Mehmet Muhtar Kocakerim (1382-1387).
Boron removal was investigated by chemical precipitation from aqueous solutions containing boron using calcium hydroxide. pH, initial boron concentration, amount of Ca(OH)2, stirring speed and solution temperature were selected as operational parameters in a batch system. The highest boron removal efficiency was reached at pH 1.0. Increasing initial boron concentration and amount of calcium hydroxide raised to boron removal efficiency. Boron removal efficiency was highest at a stirring speed of 150 rpm. The most important parameter affecting boron removal efficiency was solution temperature. Increasing solution temperature increased importantly boron removal. XRD analysis showed that CaB3O3(OH)5·4H2O, which is a borate mineral called inyoite, occurred between Ca(OH)2 and borate ions. As a result of the obtained experimental data, when the optimum operational conditions were selected, over 96% of boron removal efficiency was reached by this method.
Keywords: Boron; Removal; Recovery; Precipitation; Inyoite
Synthesis of 1-benzoylpyrene using silica-supported phosphotungstic heteropoly acid as an efficient and reusable catalyst by Minqiang He; Aixia Pan; Jimin Xie; Huamin Li; Xinhua Yuan; Xiaonong Cheng; Min Chen (1388-1392).
A novel one-pot catalytic synthesis of 1-benzoylpyrene through acylation of pyrene with benzoic anhydride catalyzed by several heteropoly acids (HPAs) was investigated. Pure 1-benzoylpyrene was obtained and its structure was identified by GC/MS, FT-IR and 1H NMR spectra. Silica-supported phosphotungstic heteropoly acid (PW/SiO2) was found to be the most active catalyst in the acylation. The yield and the selectivity of 1-benzoylpyrene were up to 62.5% and 100%, respectively. The effects of experimental parameters on the catalytic acylation reaction, and the possibility of reusability of PW/SiO2 catalyst were studied. PW/SiO2 catalyst is easily separable from the reaction mixture and reusable without loss of its activity.
Keywords: 1-Benzoylpyrene; Friedel-Crafts Acylation; Pyrene; Heteropoly Acids; Catalysis
Comparative study on the antioxidant and nitrite scavenging activity of fruiting body and mycelium extract from Pleurotus ferulae by Bok Hee Kim; DuBok Choi; Yu Lan Piao; Sang-Shin Park; Myung Koo Lee; Wol-Suk Cha; Young-Cheol Chang; Hoon Cho (1393-1402).
We investigated the effects of the antioxidant and the nitrite scavenging activities of the extracts from Pleurotus ferulae fruiting body grown on the solid state using corn cob and activated bleaching earth (CCABE media) and its mycelium grown in the liquid state. The total phenol and polysaccharide concentrations in hot water extract of fruiting body were approximately 3.6- and 4.3-fold higher than those of the mycelium. Using the hot water extract of fruiting body, the maximum DPPH radical scavenging activity at 9 mg/mL, hydroxyl radical scavenging activity at 12mg/mL, reducing power at 12 mg/mL, and chelating ability at 12 mg/mL were obtained, 80.5%, 72.4%, 0.99 OD (700 nm), and 77.0%, respectively. However, in the case of hydrogen peroxide scavenging activity, the ethanol extract was the highest, 78.7% at 12 mg/mL. The maximum nitrite scavenging activity was obtained, 89.7% at 6 mg/mL of hot water extract from fruiting body. Hot water extracts were more effective than ethanol extracts in scavenging activity on DPPH radicals and hydroxyl radical scavenging, reducing power, and chelating activity of ferrous, whereas ethanol extracts were more effective in hydrogen peroxide scavenging activity as evidenced by their lower EC50 values. These results indicate that the hot water extract of P. ferulae fruiting body using CCABE media has good potential to be used as a source of materials or additives for oxidation suppressant in food, cosmetics and drug compositions.
Keywords: Antioxidant Activity; Pleurotus ferulae ; Fruiting Body; Mycelium
Complete conversion of cellulose to water soluble substances by pretreatment with ionic liquids by Weina Liu; Yucui Hou; Weize Wu; Shuhang Ren; Wenhua Wang (1403-1408).
Pretreatment of cellulose to water soluble substances (WSS) can enhance its efficient conversion in water solvent, such as ethanol fermentation. In this work, we found ionic liquid (IL), 1-methyl-3-methylimidazolium dimethylphosphate ([Mmim][DMP]), could convert efficiently cellulose to obtain WSS, and the product WSS and IL mixture could be separated by ethanol anti-solvent way. Effects of ILs, time, temperature and water on cellulose conversion were investigated. NMR, FTIR, XRD and SEM were employed to study the mechanism of cellulose conversion with ILs. The results indicate that [Mmim][DMP] has a greater ability to interact with cellulose than [Bmim][Cl] under the same conditions. Cellulose can be completely converted into WSS in [Mmim][DMP] under all the investigated temperatures from 140 to 160 °C. Increasing temperature is beneficial to the conversion rate of cellulose. But the presence of water can decrease the conversion rate of cellulose. During the treatment by [Mmim][DMP], the hydroxyls of cellulose can form hydrogen bonds with both anion and cation of [Mmim][DMP], and after the treatment the inter- and intramolecular hydrogen bonds of cellulose and the compact structure of cellulose are collapsed.
Keywords: Cellulose; Ionic Liquids; Pretreatment; Hydrogen Bonds; Crystallinity
Immobilization of laccase on carbon nanomaterials by Jung Hee Park; Huahua Xue; Jin Suk Jung; Keungarp Ryu (1409-1412).
Laccase from Trametes versicolor was readily immobilized on carbon nanomaterials including multiwalled carbon nanotubes (MWNTs), carboxylated multiwalled carbon nanotubes (MWNT-COOHs), and graphene oxides (GOs), by physical adsorption without using coupling agents. The immobilized amount of laccase strongly depends on the pH of the aqueous buffers of the immobilization mixture. As the pH of the aqueous buffer for immobilization increases, the immobilized amount of laccase decreases. The activity of the immobilized laccase on the three carbon nanomaterials exhibits a bell-shaped dependence on the pH of the immobilization solution with maximum activity at pH 6 or 7. When the immobilization solution becomes acidic or basic, the activity of the immobilized laccase declines significantly. The amount and the activity of immobilized laccase were maximum for graphene oxides as substrate material for immobilization.
Keywords: Carbon Nanotubes; Graphene Oxides; Immobilization; Laccase; Oxidized Carbon Nanotubes
Solubility of N-chloro succinimide in different pure solvents in the temperature range from 278.15 K to 333.15K by Jing Zhu; Fei Shen; Yong-Hong Hu; Xin-min Jiang; Dong-yun Li (1413-1417).
Solubility data were measured for N-chloro succinimide in pure n-butanol, ethyl acetate, acetone, isopropanol, tetrahydrofuran, acetonitrile and acetic anhydride at the temperature range between 278.15 K and 333.15 K under atmospheric pressure by gravimetric method. The solubility of N-chloro succinimide in those selected solvents increased with increasing temperature. The solubility data were correlated with the modified Apelblat equation and the van’t Hoff equation to obtain the model parameters. The experimental results could be useful for optimizing the process of purification of N-chloro succinimide in industry. Isopropanol could be the excellent solvent in the crystallization of N-chloro succinimide.
Keywords: N-chloro Succinimide; Solubility; Measure; Correlation
Measurement and correlation of the isothermal vapor-liquid equilibrium data for carbon dioxide and dimethyl ether system by Min Hee Lee; Joon-Hyuk Yim; Jong Sung Lim (1418-1425).
Vapor-liquid equilibrium (VLE) data for the binary system of carbon dioxide (CO2)+dimethyl ether (DME) were measured at six equally spaced (10 K) temperatures between 283.15 and 333.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The equilibrium compositions of vapor and liquid phases and pressure were reported at each temperature. The experimental VLE data were correlated with PR-EoS using the Wong-Sandler (W-S) mixing rule and the universal mixing rule (UMR). The overall average values of AAD-P (%) and AAD-y through the temperature range from 283.15 to 333.15 K were 1.0% and 0.012 for the W-S mixing rule and 0.88% and 0.014 for the UMR, respectively. All values are small and acceptable. Calculated results with these equations have given satisfactory results compared with the experimental data.
Keywords: Vapor-liquid Equilibrium; Carbon Dioxide; Dimethyl Ether; Peng-Robinson Equation of State; Wong-Sandler Mixing Rule
Phase diagrams of urethanized polyvinyl alcohol with a series of hydrophobically modified pH-responsive polymers containing amino acid residues by Shaikh Asrof Ali (1426-1437).
The composition and phase diagram of aqueous two-phase systems (ATPSs) of urethanized polyvinyl alcohol (UPVA) and a series of ionic co- and terpolymers (IPs) of pH-responsive hydrophilic diallylammonioethanoate, 0–3mol% hydrophobic dodecyldiallylammonium chloride, and SO2 have been studied for the first time. The presence of unquenched nitrogen valency in the repeat units of the IPs permitted the change of the charge types and their densities in the polymer chain. The effects of zwitterionic (Z±) and anionic (A−) charge densities on the polymer backbone, salt (NaCl) concentration, and hydrophobe content on the phase diagrams were investigated. The presence of the hydrophobe in the polymer shifted the binodal downward; magnitude of the shift increased with the increase in the hydrophobe content. The phase separation happened at relatively low total polymer concentrations (much below than 10%), which could be useful in separation and purification of biomaterials.
Keywords: Aqueous Two-phase System; pH-responsive Polymers; Hydrophobicity; Urethanized Polyvinyl Alcohol; Phase Diagram
Computational study on the decomposition of tetraneopentyl zirconium for the chemical vapor deposition of zirconium carbide by Yong Sun Won (1438-1443).
The overall gas phase decomposition mechanism of tetraenopentyl zirconium precursor (Zr[CH2C(CH3)3]4) for the chemical vapor deposition of zirconium carbide thin films was investigated by using computational thermochemistry. Density functional theory (DFT) and harmonic vibrational frequency calculation were used to generate thermodynamic properties at each reaction step, based on which thermodynamic or kinetic preference of a reaction pathway was evaluated. While the preference of γ-hydrogen abstraction of neopentane over α-hydrogen abstraction was confirmed in the initial stage of ZrNp4 decomposition, they turned out to be competing instead of the dominant preference of γ-hydrogen abstraction. Methane formation at three subsequent reaction steps was explained by β-methyl migration, and the following α-hydrogen abstraction of methane based on the suggestion that α- and γ-hydrogen abstractions of neopentane are competing kinetically in previous reaction steps. Computational thermochemistry showed a possibility as a general tool to anticipate the gas phase decomposition mechanism of a precursor in chemical vapor deposition.
Keywords: Tetraneopentyl Zirconium; Zirconium Carbide; Chemical Vapor Deposition; Density Functional Theory
Preparation of spherical macroporous silica in an aerosol phase by Ki Woong Ahn; Hana Rah; Sun-Geon Kim (1444-1452).
Macroporous silica (MS) and macro/mesoporous silica (MMS) were prepared by spray drying a polystyrene (PS) latex sol containing a silica source, followed by calcination. As a silica source, 3-aminopropyl triethoxysilane (APS) was used for MS while either silica sol (SS) or tetraethoxyothosilicate using P123 templating (P123-TEOS) was used for MMS. Spray drying and calcination could also take place in a once-through aerosol reactor. The transformation of the silicon alkoxides to silica and decomposition of PS occurred at similar temperatures. Therefore, for APS-originated MS, the metal additives such as silver and nickel were required to accelerate the former. In addition, the nickel was well dispersed in the silica matrix during calcination even at 800 °C, in turn to thermally stabilize the porous structures. The wall-preforming additives were unnecessary for PS/SS and PS/P123-TEOS, since the SS drying and P123 templating, respectively, took place at lower temperature than PS decomposition. The porosities of all the porous silica prepared ranged from 0.54 to 0.57, which were close to the volume fraction of PS in the PS-alkoxides mixture solidified right after spray drying.
Keywords: Porous Media; Nanostructured Materials; Spray Drying; Spray Pyrolysis; Polystyrene Latex (PSL) Particles
Elucidation of morphological and optoelectronic properties of highly crystalline chalcopyrite (CuInSe2) nanoparticles synthesized via hot injection route by Umme Farva; Mahmood Alam Khan; Chinho Park (1453-1458).
CuInSe2 (CIS) nanoparticles have been prepared by the hot-injection method with sizes ∼25 nm, and the thermal annealing influence on the size, morphology and optoelectronic properties of crystalline CuInSe2 nanoparticles has been elucidated. Microstructural analysis of synthesized nanoparticles was performed by various characterization methods including high-resolution transmission electron microscopy (HR-TEM), Scanning TEM (STEM), Xray diffraction, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The fast Fourier transform (FFT) pattern of HR-TEM image of annealed CuInSe2 nanoparticles illustrates that the particles have quasisingle crystal tetragonal structure, as also confirmed by the XRD pattern. The HR-TEM image clearly shows the fringe widths are in order without any defect with 0.32 nm. Microstructural analysis results clearly indicate that the synthesized and air-annealed nanoparticles are in highly crystalline state with near stoichiometric atomic composition.
Keywords: Copper Indium Diselenide (CIS); Nanoparticle; Hot-injection Method; STEM; HR-TEM; XRD
Preparation of poly(vinyl alcohol)/tetraethyl orthosilicate hybrid membranes modified with TMPTMS by sol-gel method for removal of lead from aqueous solutions by Mohammad Irani; Ali Reza Keshtkar; Mohammad Ali Mousavian (1459-1465).
Poly(vinyl alcohol)/tetraethyl orthosilicate (PVA/TEOS) ion exchange hybrid membranes modified with 3-mercaptopropyltrimethoxysilane (TMPTMS) were prepared by the sol-gel method, and their applications for the removal of lead ions from aqueous solutions in a batch sorption process were studied. The functional groups of the hybrid membranes were characterized by FTIR. Batch adsorption studies such as TMPTMS content, pH, adsorbent dose, contact time, initial concentration and temperature were evaluated. The maximum adsorption capacity of lead ions was found to be 61.62mg g−1, respectively. The kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. The Freundlich and Langmuir isotherm models were applied to describe the equilibrium data. Thermodynamic parameters indicated that the lead adsorption onto the membrane is an endothermic and spontaneous process. The PVA/TEOS/TMPTMS hybrid membrane is regenerated by 0.5M HNO3/0.1 M HCl in equal ratio solution and the adsorption capacity did not change remarkably after five sorption-desorption cycles.
Keywords: PVA; TEOS; TMPTMS; Hybrid Membrane; Sol-gel; Sorption