Korean Journal of Chemical Engineering (v.31, #8)

Functionalization of magnetic nanoparticles for biomedical applications by Dung The Nguyen; Kyo-Seon Kim (1289-1305).
Interest in utilizing magnetic nanoparticles for biomedical treatments originates from their external controllability of transportation and movement inside biological objects and magnetic heat generation. Advances in nanoparticle and nanotechnology enable us to produce magnetic nanoparticles of specific morphology and to engineer particle surfaces to manipulate their characteristics for specific applications. Intensive investigations and developments have been carried out in improving the quality of magnetic particles, regarding their size, shape, size distribution, their magnetism and their surface. The magnetic nanoparticles with appropriate surface chemistry can conjugate various biomaterials such as drugs, proteins, enzymes, antibodies, or nucleotides to be used for numerous in vivo applications including MRI contrast enhancement, immunoassay, hyperthermia, drug delivery, and cell separation. Here we review both the key technical principles of magnetic nanoparticle synthesis and the ongoing advancement of biomedical treatments using magnetic nanoparticles, specifically, the advancement in controlled drug delivery and hyperthermia.
Keywords: Magnetic Nanoparticles; Controlled Synthesis; Biomedical Applications; Drug Delivery; Hyperthermia

Surface forces apparatus and its applications for nanomechanics of underwater adhesives by Dongyeop Xris Oh; Sara Shin; Hee Young Yoo; Chanoong Lim; Dong Soo Hwang (1306-1315).
Successful adhesion on wet surfaces is one of the most important challenges in biomedical engineering. Marine fouling organisms exhibit effective adhesion for wet substrates, and the measurement of adhesion forces in wet conditions is the first step toward mimicking the smart strategies of the marine organisms. Surface forces apparatus (SFA) is one of the most powerful nanomechanical tools used to directly measure time- and distance-dependent interactions between biological macromolecules or biological surfaces in an aqueous medium at the molecular level. Recently, SFA has been adapted to probe the biomechanical nature of the underwater adhesive in marine organisms. This review describes some strategies of the marine fouling organisms for successful underwater adhesion determined using SFA.
Keywords: Surface Forces Apparatus; L-3,4-Dihydroxyphenyl Alanine (DOPA); Underwater Adhesion; Complex Coacervate; Cation-π Interaction; Marine Adhesive; Underwater Adhesion

Two bimetallic Pd-Pt catalysts were prepared by wash-coating the composites of Pd-Pt/CeZrO2-Al2O3 onto cordierite monolith and they were evaluated in a tubular reactor for stability in combustion of SOFC stack flue gas at GHSV 29,280 h−1 and 1 atm. The Pd-rich catalyst showed better stability than the Pt-rich catalyst for combustion of the wet feed. Water vapor in the stack flue gas affected the catalyst activity adversely via the formation of inactive Pd(OH)2 species at the reaction temperatures of 723 and 823 K, but this effect was eliminated by raising the temperature to 923 K or above. Catalyst properties such as specific surface area, pore size and metal dispersion did not deteriorate significantly after combustion of the wet feed in the temperature range of 723-1,023 K. The presence of CeZrO2 in Al2O3 material was considered to affect the support properties favorably, leading to a kind of metal-support interaction beneficial for the combustion of the wet feed. This interaction helped to enable the Pd-Pt catalysts to maintain good stability for combusting the wet SOFC stack flue gas with the stoichiometric air-to-fuel ratio at 923 K or above.
Keywords: SOFC Stack Flue Gas Combustion; Bimetallic Pd-Pt Catalyst; CeZrO2-Al2O3 Support; Water Vapor and Temperature Effects; Catalyst Stability

Smith predictor based fractional-order PI control for time-delay processes by Truong Nguyen Luan Vu; Moonyong Lee (1321-1329).
A new fractional-order proportional-integral controller embedded in a Smith predictor is systematically proposed based on fractional calculus and Bode’s ideal transfer function. The analytical tuning rules are first derived by using the frequency domain for a first-order-plus-dead-time process model, and then are easily applied to various dynamics, including both the integer-order and fractional-order dynamic processes. The proposed method consistently affords superior closed-loop performance for both servo and regulatory problems, since the design scheme is simple, straightforward, and can be easily implemented in the process industry. A variety of examples are employed to illustrate the simplicity, flexibility, and effectiveness of the proposed SP-FOPI controller in comparison with other reported controllers in terms of minimum the integral absolute error with a constraint on the maximum sensitivity value.
Keywords: Smith Predictor; Fractional-order Proportional-integral (FOPI) Controller; Bode’s Ideal Transfer Function; Fractional Calculus

Optimal modification of an activated sludge process (ASP) evaluated by multiple performance criteria was studied. A benchmark process in BSM1 was taken as a target process. Four indexes of percentage of effluent violation (PEV), energy consumption (OCI), total volume of tanks (TV) and total suspended solid in tank5 (TSSa5), were criteria and eleven process parameters were decision variables, making up the multiple criteria optimization model, which was solved by non-dominated sorting genetic algorithm II (NSGA-II) in MATLAB. Pareto solutions were obtained; one solution (opt1) was selected based on the authors’ decision for a further analysis. Results show that the process with opt1 strategy exhibits much better performance of PEV and OCI than with the default, being improved by 74.17% and 9.97% specifically under dry influent and without control. These results indicated that the multiple criterion optimization method is very useful for modification of an ASP.
Keywords: Modification of Benchmark Process; Multiple Performance Criteria; Effluent Quality; Energy Consumption; Volume of Tanks

Experimental investigation has been done in unbaffled gas-liquid stirred tanks using dual concave blade impeller to analyze the mass transfer, power consumption and gas holdup. Optimal impeller clearance has been suggested for lower and upper impeller based on maximum mass transfer rate. Numerical modeling has been done to analyze the flow pattern for different combinations of impeller clearance. The lower impeller positioned at 0.3 of tank diameter and clearance between lower and upper impeller at 0.4 of tank diameter gave the maximum mass transfer coefficient. Scale-up criteria for mass transfer rate, power and gas holdup have been developed for optimal geometrical similar systems of unbaffled stirred tanks with dual concave impeller.
Keywords: Clearance; Gas-liquid; Gas Holdup; Mass Transfer; Power; Stirred Tanks; Unbaffled

Influence of fluid properties on bubble formation, detachment, rising and collapse; Investigation using volume of fluid method by Peyman Zahedi; Reza Saleh; Roberto Moreno-Atanasio; Kianoosh Yousefi (1349-1361).
Numerical simulations have been carried out to investigate the formation and motion of single bubble in liquids using volume-of-fluid (VOF) method using the software platform of FLUENT 6.3. Transient conservation mass and momentum equations with considering the effects of surface tension and gravitational force were solved by the pressure implicit splitting operator (PISO) algorithm to simulate the behavior of gas-liquid interface movements in the VOF method. The simulation results of bubble formation and characteristics were in reasonable agreement with experimental observations and available literature results. Effects of fluid physical properties, operation conditions such as orifice diameter on bubble behavior, detachment time, bubble formation frequency and bubble diameter were numerically studied. The simulations showed that bubble size and bubble detachment times are linear functions of surface tension and decrease exponentially with the increase in liquid density. In contrast, only a small influence of the fluid viscosity on bubble size and detachment time was observed. Bubble collapse at a free surface simulation with VOF method was also investigated.
Keywords: Bubble; Simulation; Two Phase Flow; Volume of Fluid

Metal-free mild oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran by Neha Mittal; Grace M. Nisola; Lenny B. Malihan; Jeong Gil Seo; Seong-Poong Lee; Wook-Jin Chung (1362-1367).
The potential of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-hydroxy-TEMPO radical) as an oxidant with [bis(acetoxy)-iodo]benzene (BAIB) and acetic acid (CH3COOH) as co-oxidants to convert 5-hydroxymethylfurfural (5-HMF) into 2,5-diformylfuran (2,5-DFF) was investigated. The effects of oxidant/acid dosages, choice of appropriate solvent, reaction temperature and time were determined to maximize the 2,5-DFF yield. Optimally, 66% 2,5-DFF yield was achieved in TEMPO/BAIB/CH3COOH system at 30 °C after 45 min in ethyl acetate. The reaction system is environmentally benign (metal-free) and energy efficient (mild at short reaction period). With scarce reports on 2,5-DFF production, the developed system provides an alternative route for a better access and wider application of this important platform chemical.
Keywords: 2,5-Diformylfuran; 5-Hydroxymethylfurfural; Homogeneous; Oxidation; Radical; TEMPO

Presulfidation and activation mechanism of Mo/Al2O3 catalyst sulfided by ammonium thiosulfate by Mingxing Tang; Hui Ge; Weibin Fan; Guofu Wang; Zhanjun Lyu; Xuekuan Li (1368-1376).
Mo/Al2O3 catalyst was presulfided with (NH4)2S2O3 to elucidate presulfidation and activation mechanism. It is illustrated that the Mo oxide is firstly partially sulfided during presulfidation and then in situ reduced into MoS2−x in activation, and finally sulfided to active state during hydrodesulfurization (HDS). A synergistic effect between the S2− and S6+ ions in (NH4)2S2O3 produces a positive influence on the HDS performance. The S2− ions contribute to the sulfidation of Mo ions, while the S6+ species interact with Al2O3 support, weakening the interaction of active species with support.
Keywords: Hydrodesulfurization; Ammonium Thiosulfate; Presulfidation; Activation; Support Interaction

Five tetrabutylphosphonium amino acid ionic liquids ([P4444][AA]) were prepared, characterized, and used as catalysts for solvent-free Knoevenagel condensation reactions. The tetrabutylphosphonium prolinate ([P4444][Pro]) showed excellent catalytic activity and selectivity in Knoevenagel condensation reactions of active methylene compounds with various aromatic aldehydes, and all the yields of corresponding products were more than 85% under mild conditions. Furthermore, a plausible reaction mechanism for the excellent performance of [P4444][Pro] has been proposed, and [P4444][Pro] could be used repetitively at least six times without obvious decrease in activity and quantity.
Keywords: Ionic Liquid; Knoevenagel Condensation; Aromatic Aldehydes; Active Methylene Compounds; Amino Acid

Four different membrane-electrode-assemblies (MEAs) with single and dual-layer gas diffusion layers (GDLs) at the anode and the cathode were prepared to examine polarization characteristics that rely on MEA configuration. Porous structure of single and dual-layer GDLs was investigated using a mercury porosimeter. An MEA with dual-layer GDLs at each electrode demonstrated higher performance with an air feed. To comprehend the improvement, the impedance behavior at various current densities and polarization behavior under back pressure were analyzed in terms of oxygen diffusion processes that control catalyst utilization in the gas diffusion electrode.
Keywords: Proton Exchange Membrane Fuel Cells; MEA Configuration; Gas Diffusion Layer; Microporous Layer; Water Management

Conversion of waste polystyrene through catalytic degradation into valuable products by Jasmin Shah; Muhammad Rasul Jan; Adnan (1389-1398).
Waste expanded polystyrene (EPS) represents a source of valuable chemical products like styrene and other aromatics. The catalytic degradation was carried out in a batch reactor with a mixture of polystyrene (PS) and catalyst at 450 °C for 30 min in case of Mg and at 400 °C for 2 h both for MgO and MgCO3 catalysts. At optimum degradation conditions, EPS was degraded into 82.20±3.80 wt%, 91.60±0.20 wt% and 81.80±0.53 wt% liquid with Mg, MgO and MgCO3 catalysts, respectively. The liquid products obtained were separated into different fractions by fractional distillation. The liquid fractions obtained with three catalysts were compared, and characterized using GC-MS. Maximum conversion of EPS into styrene monomer (66.6 wt%) was achieved with Mg catalyst, and an increase in selectivity of compounds was also observed. The major fraction at 145 °C showed the properties of styrene monomer. The results showed that among the catalysts used, Mg was found to be the most effective catalyst for selective conversion into styrene monomer as value added product.
Keywords: Waste Polystyrene; Catalytic Degradation; Selective Conversion; Chemical Products; Styrene Monomer

Preparation of acrylonitrile-butadiene-styrene membrane: Investigation of solvent/nonsolvent type and additive concentration by Fariba Sadat Kamelian; Seyed Mahmoud Mousavi; Ali Ahmadpour; Vahideh Ghaffarian (1399-1404).
In the present study, preparation of acrylonitrile-butadiene-styrene (ABS) membrane was investigated via phase inversion method. ABS membrane is sensitive to preparation conditions. Therefore, the effect of solvent/nonsolvent type and concentration of additive and ABS was evaluated on the morphology, tensile strength and car wash wastewater treatment. Polyethylene glycol was used as an additive. The results show that nonsolvent type significantly affects the morphology and consequently the flux and rejections of the pollution indices. Increasing concentration of additive and ABS in the casting solution leads to formation of denser and thinner membranes that have lower flux and higher rejections of the pollution indices.
Keywords: Copolymers; Mechanical Properties; Membranes; Morphology; Separation Techniques

Removal of elemental mercury from simulated flue gas by cerium oxide modified attapulgite by Donglei Shi; Yu Lu; Zhe Tang; Fennv Han; Ruoyu Chen; Qi Xu (1405-1412).
A novel catalyst CeO2/ATP was developed to remove Hg0 from coal fired gas. This is new way to use the facile, cheap and larger BET specific surface area catalyst attapulgite (ATP) as support to remove Hg0 from coal fired gas. The Hg0 removal and oxidation efficiency of CeO2/ATP (1: 1) is up to 97.75% and 92.23% at 200 °C, respectively. We also found that ATP plays an important role in improving the catalyst activity of CeO2/ATP, which can make CeO2/ATP have more stable catalyst activity at broader temperature range and obtain lower optimum activity temperature. Other influencing factors, such as temperature and flue gas environment (SO2, Cl2, NO), are also investigated in order to get a clear understanding of the experiment. The formation mechanisms are also proposed.
Keywords: Element Mercury; Attapulgite; Cerium Oxide; Catalytic Oxidation; Flue Gas

Deposition of toxic metal particles on rough nanofiltration membranes by Oluranti Agboola; Jannie Maree; Richard Mbaya; Caliphs Musa Zvinowanda; Gomotsegang Fred Molelekwa; Nora Jullok; Bart Van der Bruggen; Alexander Volodine; Chris Van Haesendonck (1413-1424).
Two nanofiltration (NF90 and Nano-Pro-3012) membranes were investigated for their capacity to remove metal ions. This study presents the effect of membrane roughness on the removal of toxic metal ions during dead end membrane filtration. Atomic force microscopy, scanning electron microscopy, WSXM software and ImageJ were used to characterize the roughness of the membranes. Gradual decrease in filtration permeate flux was observed as foulants accumulated at the interface of the membranes; filtration permeate flux varied from 20 L/m2/h to 14 L/m2/h and 11 L/m2/h to 6 L/m2/h for NF90 and Nano-Pro-3012, respectively. NF90 membrane was more prone to fouling than the Nano-Pro-3012 membrane: the percentage flux reduction was higher for NF90 (3.6%) than Nano-Pro-3012 (0.98%). The bearing ratio of the fouled NF90 exhibited a high peak of 7.09 nm than the fouled Nano-Pro-3012 with the peak of 6.8 nm.
Keywords: Particle Deposition; Flux Reduction; AFM; SEM; Roughness; Bearing Analysis

Efficient storage and utilization of CO2 in open raceway ponds for cultivation of microalgae by Mohammad Javad Asadollahzadeh; Mehdi Ardjmand; Ali Akbar Seafkordi; Seyed Mohammad Heydarian (1425-1432).
For efficient storage and utilization of CO2 in open raceway ponds, the effects of cultural and operational parameters were studied. A 10 m2 indoors raceway pond was operated to determine CO2 storage capacity, average rate of absorbed CO2 losses and mass transfer coefficient for CO2 outgassing from various pH, salinity and alkalinity regimes of culture medium; mixing velocities and culture depths. Average rate of CO2 outgassing for saltwater (35 ppt salinity) at 40 meq/L alkalinity was 40-fold higher than seawater (35 ppt salinity and 2.3 meq/L alkalinity) at pH 8. Operating at lower pHs or salinities aggravated CO2 outgassing. An empirical equation for CO2 outgassing average mass transfer coefficient, $ar K_L $ , was developed as a function of mixing velocity and depth. Nannochloropsis sp. PTCC6016 was cultivated in the pond for 14 days. Due to higher amount of outgassing, CO2 utilization efficiency declined as the productivity in the pond decreased.
Keywords: CO2 ; Open Raceway Pond; Microalgae; Utilization Efficiency; Outgassing, $ar K_L $

Improvement of fermentative production of exopolysaccharides from Aureobasidium pullulans under various conditions by Charles Seo; Hong Won Lee; Arumuganainar Suresh; Ji Won Yang; Jun Ki Jung; Yeu-Chun Kim (1433-1437).
The optimization of exopolysaccharide (EPS) production was investigated in the polymorphic fungal strain of Aureobasidium pullulans (KCTC 6081) with varying pH, nutrients concentration, and mixing parameters in batch fermentation condition. The maximum production of EPS (∼7.5 g/L) was observed at pH 4, while optimum nutrient concentration of carbon (sucrose), nitrogen (NaNO3), phosphorous (K2HPO4), and ascorbic acid was 50 g/L, 5 g/L, 1 g/L and 2 g/L, respectively. Interestingly, EPS productivity under non pH controlled fermentation conditions was 0.12 g/L/h with 400 rpm mixing, while under a controlled pH of 4, the EPS productivity was 0.21 g/L/h with 600 rpm, respectively. The fed-batch fermentation increased the EPS productivity up to 0.345 g/L/h with changing mixing conditions from 200 to 600 rpm and reached 47 g/L with 88% pullulan. Thus, pH and mixing were the key parameters for enhancing EPS production from A. pullulans. It is expected that these optimized parameters can be well used for enhanced industrial production of pullulan.
Keywords: Optimization; Fermentation; Exopolysaccharide; Agitation; Nutrients

Porous stainless steel hollow fiber has been widely used due to its high mechanical strength, excellent thermal conductivity and good sealing properties compared with other porous supports. We successfully prepared porous stainless steel hollow fibers using polyacrylonitrile (PAN) as polymer via dry-wet spinning followed by sintering through temperature programming method. The PAN concentration had an obvious impact on the structure and property of porous stainless steel hollow fiber even if it would be burned off during sintering. The results showed that the morphology could be tuned by adjusting the concentration of PAN. With increasing PAN concentration in casting solution for spinning, the viscosity was increased dramatically, resulting in much compact structures with high pure water flux (higher than 3×105 L·m−2·h−1·Pa−1). A more dense structure could be obtained by adding additive polyvinylpyrrolidone (PVP) as viscosity enhancer.
Keywords: Porous Stainless Steel Hollow Fiber; Structure; Property; Polymer Concentration

Native stipe (NS) and microwave treated stipe (MTS) of Flammulina velutipes were utilized for the biosorption of Zn2+ and Pb2+ ions from aqueous solution. The effects of pH, contact time, and initial concentration on the biosorption were studied for each metal separately. The desired pH of aqueous solution was found to be 6.0 for the removal of Zn2+ ions and 5.0 for the removal of Pb2+ ions. The percent removal of both metals was found to increase with the increase in contact time; biosorption equilibrium was established in about 60 min. The maximum biosorption of Zn2+ and Pb2+ ions from single component systems can be successfully described by Langmuir and Freundlich models; the biosorption kinetics can be accurately described by a second-order kinetic model. The present data from these studies confirms that the native and microwave treated forms of Flammulina velutipes stipe have the potential to be used for the biosorption of Zn2+ and Pb2+ ions from aqueous solution. The metal biosorption capacities of NS for Zn2+ and Pb2+ were 58.14 and 151.51 mg g−1, respectively, while the biosorption capacities of MTS for the both metals were 95.24 and 172.41 mg g−1, respectively.
Keywords: Flammulina velutipes ; Stipe; Zn2+ ; Pb2+ ; Biosorption

Scallop shell was used as a low-cost adsorbent for removal of two anionic textile dyes, Reactive Blue 19 (RB19) and Acid Cyanine 5 R (AC5R), from aqueous solutions. The adsorbent was characterized using inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The dye removal efficiency of scallop shell was determined as function of contact time, solution pH, initial dye concentration and adsorbent dosage. With increasing dye concentration, the adsorption of both dyes decreased, while it increased with increasing adsorbent dosage. Optimum removal of RB19 and AC5R was achieved at pH=6. Adsorption equilibrium data were well described by the Freundlich model. The maximum dye adsorption capacity of scallop shell as estimated from the Langmuir isotherm was 12.36 and 12.47 mg/g for RB19 and AC5R, respectively. The adsorption kinetic data showed excellent correlation with the pseudosecond-order model. It was concluded that scallop shell has a remarkable potential for the sorption of RB19 and AC5R and can be used for treatment of the dye contaminated wastewater.
Keywords: Scallop Shell; Kinetic Models; Adsorbent; Wastewater Treatment; Organic Dyes

Experimental values of the density and viscosity have been measured for binary mixtures of N-ethylaniline with isomeric butanols (1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol) at 303.15, 308.15 and 313.15 K over the entire mole fraction range. These data, the excess molar volumes, and deviation viscosity for the binary systems at the above-mentioned temperatures were calculated and fitted to Redlich-Kister equation to determine the fitting parameters and the root-mean-square deviations. The excess molar volumes, deviation viscosity and excess Gibbs energy of activation of viscous flow have been analyzed in terms of acid-base interactions, hydrogen bond, and dipole-dipole interaction between unlike molecules. The results obtained for dynamic viscosity of binary mixtures were used to test the semi-empirical relations of Grunberg-Nissan, Katti-Chaudhri, and Hind et al. equations.
Keywords: Viscosity; Excess Molar Volume; N-ethylaniline; Isomeric Butanols

New carbon composite adsorbents for the removal of textile dyes from aqueous solutions: Kinetic, equilibrium, and thermodynamic studies by Davis Castro dos Santos; Matthew Ayorinde Adebayo; Simone de Fátima Pinheiro Pereira; Lizie Daniela Tentler Prola; Renato Cataluña; Eder Cláudio Lima; Caroline Saucier; Caline Rodrigues Gally; Fernando Machado Machado (1470-1479).
New carbon composite materials were prepared by pyrolysis of mixture of coffee wastes and red mud at 700 °C with the inorganic: organic ratios of 1.9 (CC-1.9) and 2.2 (CC-2.2). These adsorbents were used to remove reactive orange 16 (RO-16) and reactive red 120 (RR-120) textile dyes from aqueous solution. The CC-1.9 and CC-2.2 materials were characterized using Fourier transform infrared spectroscopy, Nitrogen adsorption/desorption curves, scanning electron Microscopy and X-ray diffraction. The kinetic of adsorption data was fitted by general order kinetic model. A three-parameter isotherm model, Liu isotherm model, gave the best fit of the equilibrium data (298 to 323 K). The maximum amounts of dyes removed at 323 K were 144.8 (CC-1.9) and 139.5 mg g−1 (CC-2.2) for RO-16 dye and 95.76 (CC-1.9) and 93.80 mg g−1 (CC-2.2) for RR-120 dye. Two simulated dyehouse effluents were used to investigate the application of the adsorbents for effluent treatment.
Keywords: Adsorption; Aqueous Effluents; Carbon Composite; General Order Kinetic Model; Pyrolysis

Influence of thermally induced, dehydroxylated nanoclay on polymer nanocomposites by Priyanka Pandey; Smita Mohanty; Sanjay Kumar Nayak (1480-1489).
This work reports a novel approach towards a chemical-free treatment of nanoclay through extensive thermal exposure. Dehydroxylation at high temperature was utilized to enhance the influence of nanoclay on the properties of polymer. The effect of this treatment of nanoclay, on the polymer properties, with reference to Polypropylene (PP) has been investigated. The FTIR spectra revealed the successful removal of water from the intergallery spacing of the nanoclay. The maintained structural configuration of the clay was confirmed using WAXD pattern. The uniform dispersion and exfoliation of thermally treated clay layers inside the polymer matrix was confirmed through enhanced mechanical properties. Improved crystallization properties, thermal stability and flame retardant characteristic were also noticed in the nanocomposites reinforced with thermally dehydroxylated clay. This study revealed that the dehydroxylation approach of modification of nanoclay may provide much enhanced properties of polymer, without involvement of any chemical for modification.
Keywords: Chemical Free; Thermal; Dehydroxylation; Mechanical Properties

Dispersion mechanisms of Arabic gum in the preparation of ultrafine silver powder by Yingfen Li; Weiping Gan; Xiaogang Liu; Tao Lin; Bei Huang (1490-1495).
Finely divided silver micro-spheres were prepared with Arabic gum (AG) as dispersant through the chemical reaction of AgNO3 and ascorbic acid. AG dispersive mechanisms in the preparation of silver powder are proposed in the paper. The -COOH and -NH2 groups of AG reacted with Ag+ to form Ag+-AG complexes, followed by the nucleation of silver on AG polymer chains, which yielded silver spheres with an AG protection layer by reducing Ag+-AG complexes with ascorbic acid. With the steric effect of AG, the prepared silver particles exhibit improved dispersibility. UV-Vis and FTIR spectra confirmed that silver particles were stabilized by AG.
Keywords: Arabic Gum; Silver Powder; Sphere; Dispersive Mechanism; Chemical Reduction

Development of artificial neural network models for supercritical fluid solvency in presence of co-solvents by Eissa Mohamed El-Moghawry Shokir; Emad Souliman Al-Homadhi; Osama Al-Mahdy; Ayman Abdel-Hamid El-Midany (1496-1504).
This paper presents the application of artificial neural networks (ANN) to develop new models of liquid solvent dissolution of supercritical fluids with solutes in the presence of cosolvents. The neural network model of the liquid solvent dissolution of CO2 was built as a function of pressure, temperature, and concentrations of the solutes and cosolvents. Different experimental measurements of liquid solvent dissolution of supercritical fluids (CO2) with solutes in the presence of cosolvents were collected. The collected data are divided into two parts. The first part was used in building the models, and the second part was used to test and validate the developed models against the Peng-Robinson equation of state. The developed ANN models showed high accuracy, within the studied variables range, in predicting the solubility of the 2-naphthol, anthracene, and aspirin in the supercritical fluid in the presence and absence of co-solvents compared to (EoS). Therefore, the developed ANN models could be considered as a good tool in predicting the solubility of tested solutes in supercritical fluid.
Keywords: Supercritical; Fluid; Solvents; Cosolvents; Artificial Neural Networks