Showing papers in "Korean Journal of Chemical Engineering in 2004"

Physical and Electrochemical Properties of 1-Butyl-3-methylimidazolium Bromide, 1-Butyl-3-methylimidazolium Iodide, and 1-Butyl-3-methylimidazolium Tetrafluoroborate

Abstract: The density, viscosity, refractive index, heat capacity, heat of dilution, ionic conductivity, and electrochemical stability of 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium iodide ([bmim][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) were measured at room temperature or over a temperature range of 293.2 to 323.2 K. The density and refractive index values of [bmim][I] appeared to be the highest among three ionic liquids (ILs). However, the experimental viscosity values of [bmim][Br] were higher than those of [bmim][BF4], while the heat capacities and heats of dilution of [bmim][BF4] were higher than those of [bmim][Br]. The cyclic voltammogram of [bmim][br] and [bmim][BF4] indicated electrochemical windows in the stability range from 2.7 V of [bmim][[Br] to 4.7 V of [bmim][BF4].

Batch adsorptive removal of copper ions in aqueous solutions by ion exchange resins: 1200H and IRN97H

Abstract: The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2-7 for an initial copper concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient removal of copper from water and wastewater.

Organic thin film transistors: Materials, processes and devices

Abstract: For the past ten years, organic materials have been extensively investigated as an electronic material for thin film transistor (TFT) devices. Organic materials offer strong promise in terms of properties, processing and cost effectiveness and they can be used in flat panel displays, imagers, smart cards, inventory tags and large area electronic applications. In this review, we summarize the current status of the organic thin film transistors including substrate materials, electrodes, semiconducting and dielectric layers; organic thin film preparation methods; morphological studies for organic thin films; electrical characterization of gate dielectric layers and semiconducting active layers; and characterization of the OTFTs. Future prospects and investigations required to improve the OTFT performance are also given.

Operating strategies for Fischer-Tropsch reactors: A model-directed study

Abstract: A comprehensive parametric study for a Fischer-Tropsch (FT) synthesis process has been conducted to investigate the relation between process parameters and reactor characteristics such as conversion, selectivity, multiplicity, and stability. A flexible model was employed for this purpose, featuring the dependence of Anderson-Shultz-Flory (ASF) factor on composition and temperature. All variable process parameters in industrial FT reactors were subject to variation, including reaction temperature, reactor pressure, feed ratio, inlet mass flux, feed temperature, heat transfer coefficient, catalyst concentration, catalyst activity, etc. While typical trade-off was encountered in most cases, i.e., the change of a parameter in one direction enhances one aspect but deteriorating another, the change of feed conditions gave some promising results. It has been found that decreasing the feed rate (or increasing the residence time) and/or lowering the feed concentration can successfully enhance the conversion up to more than 90% for our specific case, without hurting the product selectivity as well as effectively condense the region of multiple steady states. The benefits and limitations accompanied with the variation of the parameters were discussed in detail and a rational start-up strategy was proposed based on the preceding results. It is shown that the decrease of inlet mass flux (say, 85% decrease of the feed rate or 60% decrease of the feed concentration from the nominal condition chosen here) or the decrease of H2/CO ratio (specifically, below about 0.25), or their combination can eliminate multiple steady states. The resulting unique relation between temperature and manipulated variable (i.e., coolant flow rate) appears to assure a safe arrival at the target condition at the start-up stage.

Continuous Chromatographic Processes with a Small Number of Columns: Comparison of Simulated Moving Bed with Varicol, PowerFeed, and ModiCon

Abstract: The Simulated Moving Bed process and its recent extensions called Varicol, PowerFeed and ModiCon are studied, in the case where a small number of columns are used, i.e. from three to five. A multiobjective optimization approach, using genetic algorithms and a detailed model of the multicolumn chromatographic process, is applied to optimize each process separately, and allow for comparison of the different operating modes. The non-standard SMB processes achieve better performance than SMB, due to the availability of more degrees of freedom in the operating conditions of the process, namely the way to carry out asynchronous switches for Varicol, and the different flow rates and feed concentration during the switching interval for PowerFeed and for ModiCon, respectively. We also consider the possibility of combining two non-standard operating modes in a new hybrid process, and evaluate also in this case the possible performance. Finally, a critical assessment of the results obtained and of the potential for practical implementation of the different techniques is reported.

Combustion synthesis of advanced materials: Fundamentals and applications

Abstract: The combustion synthesis (CS) of materials is an advanced approach in powder metallurgy. The number of products synthesized by CS has increased rapidly during recent years and currently exceeds 1,000 different compounds. The same features, such as high temperatures and rates, self-sustained manner of microstructure formation in non-equilibrium conditions, that make CS an attractive technology also define difficulties to study the nature and mechanisms of this process, which in turn are essential to control the properties of the synthesized materials. In this survey paper, we present results of our recent work both in fundamental studies of mechanisms for rapid reaction wave propagation in heterogeneous media and in using the CS approach to synthesize different types of advanced materials, including bio-alloys and nano-sized powders.

Recent advances in polymer reaction engineering: Modeling and control of polymer properties

Abstract: Complex reaction kinetics and mechanisms, physical changes and transport effects, non-ideal mixing, and strong process nonlinearity characterize polymerization processes. Polymer reaction engineering is a discipline that deals with various problems concerning the fundamental nature of chemical and physical phenomena in polymeriza- tion processes. Mathematical modeling is a powerful tool for the development of process understanding and advanced reactor technology in the polymer industry. This review discusses recent developments in modeling techniques for the calculation of polymer properties including molecular weight distribution, copolymer composition distribution, sequence length distribution and long chain branching. The application of process models to the design of model-based reactor optimizations and controls is also discussed with some examples.

Selective biosorption of mixed heavy metal ions using polysaccharides

Abstract: Although much research has been conducted on the separation of single species of heavy metal, the selective adsorption of two or more heavy metals in mixture is relatively little known. In this study, polysaccharide beads were prepared to selectively remove the targeted heavy metal ion from mixture. Among the biomasses, polysaccharide was examined due to its low cost and easy accessibility. In a single metal ion system, chitosan, λ-carrageenan, and alginic acid showed high affinity to mercury, copper, and lead, respectively. In the ion mixture, the same trend shown in the single metal ion solution was observed. The optimum electrolyte concentraion was investigated to adsorb the metal ion selectively, and it was possible to remove the targeted metal ion selectively with chitosan, alginic acid and λ-carrageenan at 1 mmol concentration of electrolyte. In order to demonstrate the feasibility of selective biosorption, two packed-bed reactors in series containing chitosan and alginic acid beads in each were studied and selective adsorption to Hg2+ and Pb2+, respectively, was observed.

Catalytic Cracking of n-Octane over Zeolites with Different Pore Structures and Acidities

Abstract: Catalytic cracking of n-octane has been studied over FAU, FER, MWW, MFI, BEA and MOR zeolites in order to investigate the effects of pore structure and acidity on their catalytic properties. The conversion of n-octane was largely dependent on the number of strong acid sites, while their pore structure determined the rate of catalyst deactivation due to carbon deposit. Continuous and high catalytic activity, therefore, was obtained on the MFI zeolite with sinusoidal pores and small Si/Al molar ratio, because its pores suppress the formation of large intermediate and its large number of strong acid sites accelerates the cracking of n-octane. urated hydrocarbons, they are also active for the catalytic cracking. Strong acidity, therefore, is required for the catalytic cracking, but strong acid sites simultaneously initiate a rapid deactivation of cat- alysts due to carbon deposit. As a result, catalysts suitable for the catalytic cracking of paraffin should have a large number of strong acid sites to initiate the cracking reaction by producing reactive in- termediates and specific pore structures to suppress the formation of large hydrocarbons which are converted to high boiling carbon- eous materials. The high hydrothermal stability of the catalysts is also indispensable because the catalytic cracking is operated at high temperatures in the presence of steam.

Reduction of COD and Color of Acid and Reactive Dyestuff Wastewater Using Ozone

Abstract: Wastewaters obtained from bromamine acid dye and reactive dye manufacturing were treated by ozone bubbling in a cylindrical batch reactor for the purpose of reducing COD to below 150 mg/L, which is the environmental discharge standard of the Republic of Korea. Remarkable COD reduction and decolorization were observed at pH over 11. High inlet gas flowrate and high concentration of ozone gave better results. Little precipitation was observed under the conditions of remarkable COD reduction. At pH of 11, 15 LPM of inlet gas flowrate and 89.3 g/Nm3 of ozone flowrate, the COD of bromamine acid dyestuff wastewater was reduced to 95 mg/L after 90 minutes, and the COD of reactive dyestuff wastewater was reduced to 120 mg/L after 120 minutes. Decolorization was completed after 30 minutes of reaction.

Application of Mesoporous MCM-48 and SBA-15 Materials for the Separation of Biochemicals Dissolved in Aqueous Solution

Abstract: The application of molecular sieves for the separation and purification of biological molecules has been limited because of their available pore size (>1.3 nm). With the development of synthetic mesoporous materials, the available pore size range (1.5-10 nm) has been extended. They have pores large enough to allow access for a number of biological molecules. This work investigated the use of two mesoporous materials (MCM-48 and SBA-15) with different pore sizes and structures for adsorption of cephalosporin C as a model compound of biological molecules in terms of ethanol concentration, solution pH, and temperature. It was found that these materials have the potential for the separation and purification processes of biochemicals including antibiotics, amino acids, and proteins.

Behavior of Hydrothermal Decomposition of Silk Fibroin to Amino Acids in Near-Critical Water

Abstract: The behavior of protein decomposition to amino acids in near-critical water is elucidated by using silk fibroin as a model compound. Results show that serine (Ser), aspartic acid (Asp) and other complex amino acids, obtained initially in significant amount, gradually decreased as reaction time and temperature were increased. At temperature higher than 523 K, it is likely that Gly and Ala underwent further decomposition. Regarding the effect of various additives, no significant effect on the yield of amino acids was observed with the addition of oleic acid. However, the presence of NaOH and formic acid (FA), both in 5 mol% aqueous solution, had significant effect on the yield. The effect of alkalinity and acidity, the production of amino acids was enhanced in either acidic or basic conditions.

Design considerations for groundwater remediation using reduced metals

Abstract: Use of reduced metals has attracted much attention since it possesses a great potential for eliminating reducible contaminants in groundwater such as heavy metals and chlorinated compounds. However, products of metal-mediated reactions for many chlorinated hydrocarbons have not clearly been identified. In addition, consumption of the metals, generation and release of metal ions, formation of insoluble metal oxides and hydroxides on the clean metal surface, and rise of pH inevitably accompany the reactions. Due to these properties of metal-mediated reactions, the reaction rate could decrease as the reaction proceeds, and effluent quality could decay. It was shown in this study using chlorine mass balance and GC analysis that chloroform is formed from carbon tetrachloride by reduced iron. It is also well-known that nitrate is reduced mostly to ammonia by metals, which indicates that the metal process is inappropriate for denitrification of nitrate-contaminated aquifers. These results indicate that groundwater remediation using metal process requires careful consideration for the safety of reaction products. It was also shown that mixing rate strongly affects reaction rate since metal-mediated reaction occurs on the surface of metals. In addition, reaction rate was decreased due to metal hydroxide deposition on the surface of metal granules that was seen by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. Generation of iron ions (consumption of reduced iron) released from reduction of zero-valent iron was also shown by using an ion chromatograph (IC). In this study, some methods were suggested to solve the above-mentioned problems. Acid washing appeared effective for removing corrosion products on the surface of metal granules, by which a reduction rate could be maintained high for an extended time of reaction. Use of iron sulfide decreased an extent of pH rise during metal-mediated reaction; thereby precipitation of insoluble metal (hydr)oxides is expectedly decreased. It was also shown that inexpensive iron scrap instead of fine metal powders can be used for metal processes.

Effects of adsorbate properties on adsorption mechanism in a carbon molecular sieve

Abstract: The adsorption characteristics of six pure components (N2, O2, Ar, CO, H2, and CH4) on a CMS were studied over a wide pressure range up to 15 arm by using a volumetric method. Despite only relatively small differences in the kinetic diameters of the probe molecules used, very large differences in the magnitude of apparent time constants were observed. The adsorption kinetic characteristics of six components on the CMS were affected by the relative importance of atomic/molecular size, shape, and polar properties. Especially, the interaction properties of adsorbate molecules were proposed as an important factor to estimate the relative adsorption rate.

Effect of Phenol on β-Carotene Content in Total Carotenoids Production in Cultivation of Rhodotorula glutinis

Abstract: The composition of carotenoids produced byR. glutinis was observed to be dependent upon the addition of phenol into medium. A stimulatory effect of phenol on Β-carotene ofRhodotorula glutins K-501 grown on glucose was investigated. Carotenoids produced byRhodotorula glutinis K-501 were identified to torularhodin, torulene and Β-carotene, whose composition was 79.5%, 6.4% and 14.1%, respectively. The Β-carotene content increased up to 35% when phenol was added to culture media at 500 ppm. The ratio of torularhodin decreased with increasing phenol concentration, while torulene content was almost constant.

A physiological study on growth and dibenzothiophene (DBT) desulfurization characteristics of Gordonia sp CYKS1

Abstract: Physiological characteristics of DBT desulfurization and cell growth ofGordonia sp. CYKS1 were investigated. It exhibited a preference to ethanol in a medium containing two carbon sources, ethanol and one of the carbohydrates used, glucose, sucrose, maltose, and galactose although it consumed both carbon sources simultaneously. Cell growth on ethanol or glucose followed the Monod kinetics. The optimal range of pH for the desulfurization of DBT and the cell growth was 7 to 8. The desulfurization rate decreased about 30% at pH 6, and no significant desulfurization or cell growth was observed at pH 5. As the initial DBT concentration increased up to 1.5 mM, the desulfurization rate also increased while no significant changes in the growth rate were observed. The maximum desulfurization rate was 12.50 μmol L-1 h-1 at an initial DBT concentration of 1.5 mM. Cell growth and desulfurization activity were severely inhibited by the presence of 2-hydroxybiphenyl (2-HBP). When 0.05 mM of 2-HBP was added at the beginning, both of the desulfurization rate and cell growth rate decreased about 20%. It was found that cell growth and desulfurization were completely inhibited in the presence of 2-HBP at 0.15 mM or a higher concentration. The inhibition by 2,2′-dihydroxybiphenyl (DHBP) was less severe than 2-HBP. About 80% of desulfurization activity was retained in the presence of 2,2′-DHBP at 0.4 mM.

Solid extraction of caffeine and theophylline from green tea by molecular imprinted polymers

Abstract: This paper involves a feasibility study on using molecular imprinted polymers as the sorbent materials in solid phase extraction for caffeine and theophylline from green tea. Two kinds of MIPs, with caffeine-theophylline mixture and pentoxifylline-theophylline mixture as the templates respectively, MAA as the monomer, EDMA as the crosslinker and ATBN as the initiator, were applied to this purpose. Mixture solution of caffeine and theophylline (1 Μg/ ml in acetonitrile) was applied to the solid extraction cartridges following a load, wash and elute procedure with acetonitrile, methanol, methanol-acetic acid (90/10, v/v) as the solvents, respectively. This solid phase extraction protocol was applied for extraction of caffeine and theophylline from green tea. Comparison between the results obtained with the MIPs cartridges and a traditional C18 reversed-phase cartridge was made. It showed that the MIP-based sorbent on the solid phase extraction was comparable with that of C18 material. HPLC analysis using a C18 column (5 Μm, 250× 4.6 mm from Rstech corporation), methanol: water (60 :40, v/v) as the mobile phase at a flow rate of 0.6 ml/min was applied for the quantitative determination.

Effect of surface hydroxyl groups of pure TiO2 and modified TiO2 on the photocatalytic oxidation of aqueous cyanide

Abstract: It is still debatable whether the photocatalytic oxidation of cyanide proceeds via hydroxyl radicals or by photogenerated holes. We synthesized pure TiO2 catalysts via sol-gel process. In order to elucidate the oxidation pathway of cyanide, we used hydroxyl radical scavengers and controlled the concentration of surface hydroxyl group on the catalysts adopting fluoride-exchange. The degree of fluoride-exchange of TiO2 catalysts was independent of the pH of suspension. We also adopted a polyoxometalate, tungstophosphoric acid (TPA, H3PW12O40) which is well known for high charge transfer ability and hydrolytic stability. TPA-modified TiO2 catalysts were prepared with sol-gel technique to overcome the high solubility of TPA in water. As another attempt for the insoluble TPA, proton of TPA supported on TiO2 catalysts was replaced by cesium ion to form Cs-TPA/TiO2 catalysts. Both attempts were successful in immobilizing TPA on TiO2 catalysts. Commercially available TiO2 catalysts such as P25 from Degussa AG were also used as catalysts. XRD analysis revealed that pure TiO2 and TPA-modified TiO2 catalysts prepared by sol-gel process were composed of well-developed anatase crystalline structure. In the presence of hydroxyl radical scavengers, the photoactivity of TPA-modified TiO2 catalysts was retarded much less than that of pure TiO2 catalysts. The concentration of surface hydroxyl group was effectively suppressed by the fluoride-exchange causing the decrease of the activity of the catalysts. In the case of fluoride-exchanged catalysts, the drop in activity was obvious for the pure TiO2 catalysts in the presence of iodide as a hydroxyl radical scavenger suggesting that indirect oxidation via hydroxyl radicals was the preferential reaction pathway. For the TPA-modified TiO2 catalysts, meanwhile, the diminution was such a small extent suggesting that direct oxidation by photogenerated holes was the main reaction pathway. The activity arising from TPA in the catalysts was due to the Keggin structured anion (PW12O 40 3- ) which acted as an electron relay with the aid of dissolved oxygen in the reaction system.

Effect of Heat Transfer on the Transient Dynamics of Temperature Swing Adsorption Process

Abstract: The effect of radial heat transfer on temperature swing adsorption (TSA) was studied by using an air-drying TSA experiment. The experimental dynamics of water adsorption and thermal regeneration in a fixed bed packed with zeolite 13X were used to evaluate the predicted results from the developed models. One- and two-dimensional models for energy balance with various equations describing internal velocity were compared in terms of the prediction of transient dynamics of TSA. Since the heat effect in adsorption step depended on the isosteric heat of adsorption, a dynamic simulation was performed under adiabatic, near-adiabatic, and constant wall temperature conditions. A com- parison between one- and two-dimensional models was also made under near-adiabatic condition, which reflected on the experimental condition. There was little difference between adsorption breakthrough curves predicted by the one- and two-dimensional models because the radial distribution of temperature was negligible at the adsorption step. In the case of the regeneration step, a small difference between two models was expected just at the early period of time because the radial effect disappeared with time. One-dimensional model could provide an adequate prediction of the transient dynamics in this system when the wall energy balance was included.

Combined performance of electrocoagulation and magnetic separation processes for treatment of dye wastewater

Abstract: In this study, a combined system of electrocoagulation (EC) and magnetic separation (MS) has been applied to the treatment of dye wastewater, and its performance has been evaluated. The floes formed in the electrocoagulation using Fe anode are magnetized and thus they could be removed by magnetic separation. The removal of suspended solids, color and COD was improved with an increase in electric current up to about 15 A and with a decrease in liquid velocities in EC. While the remaining suspended solids in the treated water were reduced to a few ppm and the color was removed almost perfectly (Max. 96%), that of COD was relatively low and only 81%. A further powerful operation can be expected from the present system if it is combined with an additional process, such as electrolysis or oxidation, to reduce COD more efficiently.

One-through Selective Separation of Copper, Chromium and Zinc Ions by Hollow Fiber Supported Liquid Membrane

Abstract: The separation of a mixture of Cu(II), Cr(VI) and Zn(II) simultaneously from a sulfate media using two consecutive hollow fiber microporous liquid membrane extraction systems has been studied. The experiments were made in the one-through mode. LIX84-I and Aliquat336 were used as carrier extractants for copper and chromium in the first and second hollow fiber modules, respectively. Pure copper and pure chromium ions are extracted and stripped from first and second hollow fiber modules, respectively, but zinc ions cannot be extracted by both extractants due to pH conditions used in this study and remain in the raffinate. Results indicate that the percentage of extraction is highly dependent on pH of the feed solution and the pH value is 2.5 for the maximum extraction. The percentage of extraction of copper and chromium ions is enhanced when the concentration of LIX84-I and Aliquat336 is increased of which both maximum value is 0.5 M, and these results also occur in stripping phase. The influence of sulfuric acid and sodium hydroxide concentration in strip solution of each column was examined, and it was found that the percentage of extraction and stripping is further increased due to the difference of driving force. The maximum percentage of extraction for copper is 33% and 92% for chromium. The experimental results indicated the feasibility of separation and recovery of these metals from the dilute solution by using membrane technology

Fenton oxidation process control using oxidation-reduction potential measurement for pigment wastewater treatment

Abstract: The Fenton oxidation process was applied as a pretreatment process to degrade non-biodegradable organic matters in pigment wastewater. It was necessary to continuously measure the fluctuating concentration of organics in the pigment wastewater and to determine the amount of Fenton’s reagent required to oxidize the organics. Batch and continuous flow tests were used to evaluate the relationship between the concentration of organics (CODCr) and the amount of Fenton’s reagent required to achieve a sufficient oxidation of the organics. On-line measurements of the oxidation-reduction potential (ORP) value in the batch and continuous flow tests showed that the maximum ORP values were highly related to the organic concentrations (expressed as CODCr) and the Fenton’s reagent dosage (expressed as H2O2 concentration). The empirical equation was [CODCr]=8808+0.494[H2O2]-14.6ORP. A control program of Fenton’s reagent dosage based on the empirical equation was applied to control of a pilot scale Fenton oxidation process using ORP measurement. The concentration of organics predicted with the control program well agreed with the observed concentration of organics in the pigment wastewater. The variation of the effluent organics concentration of the controlled Fenton oxidation process was significantly reduced compared to that of a process without the control system. These results suggested that the control system of Fenton’s reagent dosage using ORP measurement would be applicable to the Fenton oxidation process for efficient pretreatment of pigment wastewater.

Adsorption Behavior of Aqueous Europium on Kaolinite under Various Disposal Conditions

Abstract: 3+ exists mainly at pH 5 or below and solid phases of Eu(OH) 3(s), Eu(OH)CO3(s), and Eu2(CO3)3·3H2O(s) are formed at higher pH ranges. Adsorption behavior of Eu on kaolinite in the low pH range can be explained by interlayer ion-exchange reaction. The significant increase in adsorbed amount at pH 5-6 is due to the surface complexation at the edge site of kaolinite. In the high pH range, precipitation of Eu contributes mainly to the ad- sorption quantity. The rapid decrease in adsorbed amount above pH 7 under 10% CO 2 condition occurs by the forma- tion of anionic europium species of Eu(CO 3)2 - . The adsorption of Eu on kaolinite could be well interpreted by the Freundlich adsorption isotherm. The data except for the highest equilibrium concentration ranges were also explained by Langmuir isotherm and the maximum adsorbed quantity of Eu on kaolinite, b, is 1.2 mg/g.

Effects of Charge Density on Water Splitting at Cation-Exchange Membrane Surface in the Over-Limiting Current Region

Abstract: To determine the correlation between surface properties and concentration polarization (CP) behaviors, cation exchange membranes with varying fixed charge densities were prepared and characterized by using several electrochemical analyses such as chronopotentiometry, zeta potential, and current-voltage measurements. Results showed that CP behavior depended mainly on surface charge density. With higher surface charge density, stronger electroconvection was observed, suggesting that an increase in the surface charge density increased the concentration of the counter ions at the membrane surface. As such, the electric field around the membrane surface was strengthened at a current over the limiting current density. Water splitting was also proportional to the surface charge density. This result was consistent with the classical electric field-enhanced water splitting theory, indicating that water splitting increased due to increases in the electric field and prepolarization of water molecules at the membrane-solution interface of the cation-exchange membrane.

Density Correlation of Solubility of C. I. Disperse Orange 30 Dye in Supercritical Carbon Dioxide

Abstract: The solubility of C. I. Disperse Orange 30 (O30) dye in CO2 has been measured by using a closed-loop (batch) solid-fluid equilibrium apparatus at temperatures between 313 and 393 K and at pressures between 11 and 33 MPa. Kumar and Johnston’s equation based on Chrastil’s concept has been used to describe the experimental solubility data. The solubility versus density plot appears much simpler than the solubility versus pressure plot. The isotherms are nearly straight and parallel to each other, as seen in the previous studies. Peng-Robinson equation of state (PR EOS) has also been used successfully in modeling the dye solubility in supercritical carbon dioxide as a function of pressure or density of the fluid phase. The validity of this method has been verified by the vapor pressure calculation.

Formation of Chlorite and Chlorate from Chlorine Dioxide with Han River Water

Abstract: This study was designed to elucidate the behavior of chlorine dioxide in drinking water systems. Furthermore, the factors that influence the formation of chlorite, chlorate in terms of reaction time, concentration of chlorine dioxide, pH, temperature and UV irradiation were experimentally reviewed. At 20 ‡C, pH 7, 70–80% of chlorine dioxide injected was converted to chlorite and 0–10% of that was transformed into chlorate within 120 min with 2.91 mg/L of DOC. The amount of chlorite formed also increased when pH and temperature increased. As DOC content increased, the residual chlorine dioxide decreased but the amount of chlorite and chlorate were increased. These experiments revealed that chlorate was a dominant by-product under UV irradiation. The models that were obtained by the regression analysis for the formation of chlorite and chlorate from chlorine dioxide with Han River water are as follows: Chlorite (mg/L)=10-2.20[ClO2]0.45[pH]0.90[temp]0.27[TOC]1.04[time]0.20, Chlorate (mg/L)=10-2.61[ClO2]1.27[pH]-0.50[temp]1.28 [TOC]0.31[time]0.12

Behavior of Amino Acid Production from Hydrothermal Treatment of Fish-Derived Wastes

Abstract: The effect of operating parameters (temperature and time) and various reaction modes(batch, semi-batch and continuous flow) on the behavior of amino acid production from hydrothermal decomposition of fish-derived wastes was investigated. The amino acids obtained in batch experiments at 523 K were mainly alanine (Ala) and glycine (Gly) at maximum yield of 65 and 28 mg/g-dry fish, respectively. At a relatively lower temperature of 473 K, the relative concentration of high-molecular-weight amino acids such as aspartic acid (Asp) and serine (Ser) is significantly high, but decreases as temperature increases. It is likely that high-molecular-weight amino acids decompose faster than low-molecular ones. Semi-batch and continuous flow modes of reaction suppressed decomposition of amino acids into organic acids (or volatile materials) by continuously removing the products from the reaction zone as soon as they were formed. Thus, a large amount of high-molecular-weight amino acids such as Asp and Ser at these reaction modes was observed. This increases the yield of total amino acids at short reaction time and at temperature relatively higher than 523 K. It was also observed that the composition of the resulting products also depends on the modes of reaction.

An Optimization Strategy for Nonlinear Simulated Moving Bed Chromatography: Multi-Level Optimization Procedure (MLOP)

Abstract: This paper presents a multi-level optimization strategy to obtain optimum operating conditions (four flow-rates and cycle time) of nonlinear simulated moving bed chromatography. The multi-level optimization procedure (MLOP) approaches systematically from initialization to optimization with two objective functions (productivity and desorbent consumption), employing the standing wave analysis, the true moving bed (TMB) model and the simulated moving bed (SMB) model. The procedure is constructed on a non-worse solution property advancing level by level and its solution does not mean a global optimum. That is, the lower desorbent consumption under the higher productivity is successively obtained on the basis of the SMB model, as the two SMB-model optimizations are repeated by using a standard SQP (successive quadratic programming) algorithm. This approach takes advantage of the TMB model as well as surmounts shortcomings of the TMB model in the general case of any nonlinear adsorption isotherm using the SMB model. The MLOP is evaluated on two nonlinear SMB cases characterized by i) quasi-linear/non-equilibrium and ii) nonlinear/nonequilibrium model. For the two cases, the MLOP yields a satisfactory solution for high productivity and low desorbent consumption within required purities.

Influence of Chain Length of Tertiary Amines on Extractability and Chemical Interactions in Reactive Extraction of Succinic Acid

Abstract: Reactive extraction of succinic acid from aqueous solutions with various tertiary amines dissolved in 1-octanol and in n-heptane has been studied as a function of the chain length of the tertiary amine. In the tertiary amine extractants in 1-octanol, the extractabilities of tertiary amines were proportional to their chain length. But, in n-heptane, the extractabilities of tertiary amines decreased with their chain length. In order to analyze chemical interactions involved in the complexation of succinic acid with amine extractants in 1-octanol and n-heptane, infrared (IR) spectroscopy was used. From IR spectroscopy, it was found that the difference of extractability in 1-octanol and in n-heptane was mainly due to the different degree of intramolecular hydrogen bonding of succinic acid with the polarity of diluents. And the possible stoichiometry of acid-amine-diluent complex was predicted as (1,1), (2,1), (1,1,1).

Imaging nanostructured fluids using cryo-TEM

Abstract: Cryogenic transmission electron microscopy (cryo-TEM) has gained increasing popularity among researchers in the field of amphiphilic self-assembly as an experimental method of choice because of its unique ability to visualize nanostructures in complex fluids. Due to many recent technical improvements in the instrumentation, cryo-TEM experiments are now common. However, some limitations and possible artifacts are still a problem, and awareness of them remains a prerequisite for reliable operations and interpretation. The goal of this paper is to provide a review of the basic methods and procedures by which the cryo-TEM experiments are typically practiced. As examples, this paper also presents recent results derived from our cryo-TEM studies of micellization of block copolymer blends which clearly illustrate the unique usefulness of the technique for exploring the unexpected, complex, and/or heterogeneous nanostructures in amphiphilic solutions.