Korean Journal of Chemical Engineering (v.31, #7)

Organic solar cells based on conjugated polymers : History and recent advances by Hwajeong Kim; Sungho Nam; Jaehoon Jeong; Sooyong Lee; Jooyeok Seo; Hyemi Han; Youngkyoo Kim (1095-1104).
Organic solar cells have attracted huge attention because of their potential in the low-cost manufacturing of plastic solar modules featuring flexible, lightweight, ultrathin, rollable and bendable shapes. The power conversion efficiency of organic solar cells is now passing ~10%, which is a critical sign toward commercialization because organic solar cells surpass any other types of solar cells in terms of development speed. The encouraging efficiency enhancement could be realized by introducing a ‘bulk heterojunction’ concept that overcomes the weakness of organic semiconductors by minimizing their charge transport paths through making effective p-n junctions inside bulk organic films. However, there are several hurdles for commercialization, including stability and lifetime issues, owing to the bulk heterojunction concept. This review summarizes the important aspects of organic solar cells, particularly focusing on conjugated polymers as an active layer component.
Keywords: Organic Solar Cells; Power Conversion Efficiency; Bulk Heterojunction; Conjugated Polymer; Flexible; Charge Transport

Synthesis of copper nanoparticles : An overview of the various methods by Bahareh Khodashenas; Hamid Reza Ghorbani (1105-1109).
The synthesis of metal nanoparticles has received much attention due to their wide range of applications. Copper nanoparticles have attracted much attention due to their unique optical and electrical properties. Copper is relatively cheap in comparison to precious metals like gold and silver and also has high antibacterial properties. This review gives a brief overview of the available research works considering the synthesis of copper nanoparticles by chemical, physical, and biological methods.
Keywords: Copper Nanoparticle; Synthesis; Chemical; Physical; Biological

Although fossil fuels play an important role as the primary energy source that currently cannot be replaced easily with other energy sources, their depletion and environmental impact are becoming major concerns. Improvements in energy efficiency are believed to solve both problems simultaneously. We examined the relationships between the improvement in energy efficiency, energy usage and CO2 emissions in industry, especially in the distillation process. The energy efficiency improvement of dimethyl ether (DME) purification performed with dividing-wall column distillation (DWC) and acetic acid recovery performed with mechanical vapor recompression (MVR) were evaluated by recalculating the amount of fuel burnt and its CO2 emission. The results showed that the paradigm of lower energy being directly proportional to lower CO2 emissions is not entirely correct. To avoid this confusion, a tool for examining the uncommon behavior of various systems was developed.
Keywords: Energy Efficiency Improvement; CO2Emissions; Distillation; Fossil Fuel; Industry

The measurement of particulate matter induced oxidative potential activity by dithiothreitol (DTT) as an alternative quantitative method has been of recent interest. The mechanism of this process is not well understood. Proposed mechanisms often involve formation of the hydrogen peroxide as the final step. Evidence suggests that this may not be the dominant route. We applied computational methods to determine a possible alternative mechanism in the presence of ·OH radical production. An energetically favored mechanism was found for DTT-chemical reactivity reaction which is consistent with previously reported experimental results.
Keywords: Particulate Matter; Dithiothreitol; Oxidative Potential Activity; Density Functional Theory

Performance enhancement and energy reduction using hybrid cryogenic distillation networks for purification of natural gas with high CO2 content by Khuram Maqsood; Jayita Pal; Dhanaraj Turunawarasu; Anindya Jyoti Pal; Saibal Ganguly (1120-1135).
A novel concept of hybrid cryogenic distillation network has been explored which maximizes the benefits of both desublimation or solid-vapor based separation as well as distillation or vapor-liquid equilibrium based separation during the separation of carbon dioxide from methane or natural gas. Process network synthesis has been performed for four case studies with high carbon dioxide (72 mole%) and medium carbon dioxide (50 mole%) natural gas feed streams. The benefits of optimal locations for cryogenic packed beds were investigated. A conventional cryogenic network consisting of multiple distillation columns with butane as additive for extractive distillation was also studied and presented in this paper. Process modeling of cryogenic distillation network with MESH equations was attempted using an integrated dual loop (C+3) convergence and the results were compared with Aspen Plus simulator for benchmarking. The prediction of solidification region was employed using experimental data from literature to avoid solidification regions in the column. The proposed hybrid cryogenic distillation network showed promising potential for energy and size reduction.
Keywords: Hybrid Cryogenic Distillation Network; Modeling; Natural Gas Purification; CO2 Capture

A novel approach to the design and operation scheduling of heterogeneous catalytic reactors by Kamlesh Ghodasara; Robin Smith; Sungwon Hwang (1136-1147).
A number of studies have been conducted to reduce the overall level of catalyst deactivation in heterogeneous catalytic reactors, and improve the performance of reactors, such as yield, conversion or selectivity. The methodology generally includes optimization of the following: (1) operating conditions of the reaction system, such as feed temperature, normal operating temperature, pressure, and composition of feed streams; (2) reactor design parameters, such as dimension of the reactor, side stream distribution along the axis of the reactor beds, the mixing ratio of inert catalyst at each bed; and (3) catalyst design parameters, such as the pore size distribution across the pellet, active material distribution, size and shape of the catalyst, etc. Few studies have examined optimization of the overall catalyst reactor performance throughout the catalyst lifetime, considering catalyst deactivation. Furthermore, little attention has been given to the impact of various configurations of reactor networks and scheduling of the reactor operation (i.e., online and offline-regeneration) on the overall reactor performance throughout the catalyst lifetime. Therefore, we developed a range of feasible sequences of reactors and scheduling of reactors for operation and regeneration, and compared the overall reactor performance of multiple cases. Furthermore, a superstructure of reactor networks was developed and optimized to determine the optimum reactor network that shows the maximum overall reactor performance. The operating schedule of each reactor in the network was considered further. Lastly, the methodology was illustrated using a case study of the MTO (methanol to olefin) process.
Keywords: Modeling; Optimization; Kinetics; Reactor; Deactivation

Computational fluid dynamics simulations of interphase heat transfer in a bubbling fluidized bed by Musango Lungu; Jingyuan Sun; Jingdai Wang; Zichuan Zhu; Yongrong Yang (1148-1161).
Numerical simulations based on the Eulerian-Eulerian approach have been performed in the study of interphase heat transfer in a gas solid fluidized bed. The kinetic theory of granular flow (KTGF) has been used to describe the solid phase rheology. An assessment of drag models in the prediction of heat transfer coefficients shows that no major difference is observed in the choice of the drag model used. Fluctuations of the interphase heat transfer coefficient have been found to be closely related to the bubble motion in the bed. Effects of the wall boundary condition, inlet gas velocity, initial bed height and particle size on the predicted heat transfer coefficient have also been investigated. Typical temperature profiles in the bed show that thermal saturation is attained instantaneously close to the gas distributor. Simulated results of the coefficients are in fair agreement with those reported in literature.
Keywords: CFD; Drag Model; Fluidization; Heat Transfer; Simulation

Nanostructured γ-Al2O3 with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, BET, TPR, TPH, SEM and TPO techniques. The BET analysis showed a high surface area of 204m2g−1 and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The results revealed that an increase in nickel loading from 5 to 15 wt% decreased the surface area of catalyst from 182 to 160 m2g−1. In addition, the catalytic results showed an increase in methane conversion with increase in nickel content. TPO analysis revealed that the coke deposition increased with increasing in nickel loading, and the catalyst with 15 wt% of nickel showed the highest degree of carbon formation. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Increasing CO2/CH4 ratio increased the methane conversion. The BET analysis of spent catalysts indicated that the mesoporous structure of catalysts still remained after reaction.
Keywords: Nanostructured; γ-Al2O3 ; Nickel Catalyst; Dry Reforming; Syngas

Effect of La2O3 promoter on NiO/Al2O3 catalyst in CO methanation by Hongyun Qin; Cuili Guo; Yuanyuan Wu; Juntao Zhang (1168-1173).
A series of NiO/Al2O3 catalysts promoted by different La2O3 contents were prepared by impregnation method. The physicochemical properties of NiO-La2O3/Al2O3 were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR) and H2 chemisorption. The effect of La2O3 on the activity of NiO/Al2O3 for CO methanation was investigated in a fixed bed reactor. A lifetime test, as well as thermogravimetric (TG) analysis, was performed to investigate the stability performance and anti-carbon deposition of catalysts. The results showed that the addition of La2O3 can restrain the growth of NiO particles, increase the H2 uptake and Ni dispersion, and therefore enhance the activity of catalysts. When the La2O3 content was 3 wt%, a CO conversion of 98% and a selectivity to CH4 of 96% were obtained at 400 °C. Furthermore, the catalyst NiO-La2O3/Al2O3 with 3 wt% La2O3 content displayed highly stable performance in long-term tests, especially exhibiting good anti-carbon deposition property.
Keywords: CO Methanation; La2O3 ; Promoter; NiO/Al2O3 Catalyst; Stability

Hydrogenolysis of nitrosodimethyl amine in gas phase over Au/γ-Al2O3 nanocatalyst by Shahram Ghanbari Pakdehi; Fariba Fazeli (1174-1179).
Nitrosodimethyl amine (NDMA), as a carcinogenic byproduct in production of unsymmetrical dimethyl hydrazine (UDMH) in space industries, should be decomposed in the vapor phase. A suitable method for this purpose is selective catalytic hydrogenolysis of NDMA over Au/γ-Al2O3 nanocatalyst. We synthesized and characterized the Au/γ-Al2O3 nanocatalyst by homogeneous deposition-precipitation (HDP)/DP-urea method. Activity of the catalyst was influenced by nanosized Au particles, Au loading and the bed temperature. The optimum parameters for the catalyst were: Au particles <5 nm, Au loading at 1.5 wt% and bed temperature of 35–45 °C. The reaction was strongly sensitive to the Au particle size. The reaction occurred over the catalyst to produce dimethyl amine (DMA) and nitroxyl in a selective manner. The kinetics of NDMA hydrogenolysis over the nanocatalyst was studied in an integral fixed bed reactor. There existed a consistency with the Langmuir-Hinshelwood mechanism involving dissociative adsorption of H2 and NDMA.
Keywords: NDMA Hydrogenolysis; au/γ-Al2O3 ; Nanocatalyst; Effective Parameters; Au Particle Size; Kinetics

Utilization of lignocellulosic waste for ethanol production : Enzymatic digestibility and fermentation of pretreated shea tree sawdust by Augustine Omoniyi Ayeni; James Abiodun Omoleye; Sandeep Mudliar; Fredrick Kofi Hymore; Ram Awtar Pandey (1180-1186).
Enzymatic hydrolysis and fermentation methods were evaluated on alkaline peroxide pretreated shea tree sawdust conversion to ethanol. Optimum pretreatment conditions of 120 °C reaction temperature, 30 min reaction time, and 20 mL L−1 of water hydrogen peroxide concentration (1%(v/v)H2O2) solubilized 679 g kg−1 of hemicellulose and 172 g kg−1 of lignin. 617 g kg−1 cellulose was retained in the solid fraction. The maximum yield of reducing sugar with optimized enzyme loadings by two enzyme preparations (cellulase and β-glucosidase) was 165 g kg−1 of dry biomass. The ethanol yield was 7.35 g L−1 after 72 h incubation period under the following conditions: 2% cellulose loading, enzyme concentration was 25 FPU (g cellulose)−1 loading, yeast inoculums was 10% (v/v), 32 oC, and pH 4.8. The pretreatments gave information about the hindrances caused by lignin presence in lignocellulosic materials and that hemicelluloses are better hydrolyzed than lignin, thereby enhancing enzymatic digestibility of the sawdust material.
Keywords: Alkaline Peroxide Oxidation; Vitellaria paradoxa ; Pretreatment; Enzymatic Hydrolysis; Lignocellulosic Biomass

We prepared polyvinylchloride based nanocomposite heterogeneous cation exchange membranes by solution casting technique using cation exchange resin powder as functional groups agent and tetrahydrofuran as solvent. Silver nanoparticles were also used as fillers in membrane fabrication. The effect of silver nanoparticles concentration in casting solution on membrane physico/chemical and antibacterial characteristics was studied. The SEM images showed compact structure for the modified membranes. X-ray diffraction results also revealed that membrane crystallinity was clearly changed by increase of nanoparticle concentration. Membrane selectivity and transport number were enhanced initially by increase in nanoparticle content up to 4%wt in prepared membrane, and then showed decreasing trend by more increase in additive concentration from 4 to 8%wt. Selectivity and transport number were enhanced another time by further increase in nanoparticle loading ratio from 8 to 16%wt. Opposite trend was found for the membranes’ average grain size by variation in additive content. Ionic flux was also clearly enhanced by using Ag nanoparticles in membrane matrix. Moreover, modified membranes showed good ability in decrease of Escherichia coli growth rate.
Keywords: Mixed Matrix Membrane; Ion Exchange; Silver Nanoparticles; Fabrication/Characterization; Antibacterial Property/Escherichia coli Growth Rate

Designing and operating a pilot plant for purification of industrial wastewater from toxic organic compounds by utilizing solar energy by Mohammad Fadhil Abid; Mohammed Ebrahim; Orroba Nafi; Luma Hussain; Neran Maneual; Abeer Sameer (1194-1203).
The aim of the present project was to design and operate a solar reactor system and to analyze its performance for the removal of different types of toxic organic pollutants (e.g., synthetic methyl violet dye and phenol) from water with titanium dioxide as the photocatalyst. Various operating parameters were studied to investigate the behavior of the designed reactor like initial substrate concentration, loading of catalyst, pH of solution, and H2O2 concentration. The operating parameters were optimized to give higher efficiency to the reactor performance. Results showed that a photocatalysis system, operating at optimum conditions, offered within one hour of operation degradation up to 95.27% for synthetic dye, while a conversion of 99.95% was obtained in three hours. With phenol, degradation was up to 80.0% and 98.0%, respectively. The removal of TOC for the two toxic materials was also at high levels. This confirmed the feasibility of the designed solar system. The kinetics of dye degradation was first order with respect to dye concentration and could be well described by Langmuir-Hinshelwood model. A preliminary design of a solar photocatalysis system as an alternative treatment method for wastewater effluents from an Iraqi textile mill was introduced.
Keywords: Solar Photocatalysis; Dye Synthetic Wastewater; Phenol Removal; Degradation Kinetics; Solar Reactor Design

La-promoted Ni/γ-Al2O3 catalyst for autothermal reforming of methane by Mahmood Alam Khan; Seong Ihl Woo (1204-1210).
Autothermal reforming (ATR) of methane over the synthesized catalysts of 10Ni-2La/γ-Al2O3, 10Ni-2Ce/γ-Al2O3, 10Ni-2Co/γ-Al2O3 was investigated in the temperature range of 600-800 oC for the hydrogen production. The sequence of 2 wt% metal loading on nickel alumina support in relation to their catalytic performance was observed as La>Ce>Co. The excellent activity and selectivity of 10Ni-2La/γ-Al2O3 was superior to other catalysts owing to little carbon deposition (~2.23 mg coke/gcath), high surface area and good dispersion and stability in the alumina support. The reforming of methane was inferred to be initiated by the decomposition of hydrocarbon at the inlet zone, preceded by the reforming reactions in the catalyst bed. Our result shows that it can be possible to achieve the H2/CO ratio optimal to the GTL processes by controlling the O2/CH4 ratio of the feed inlet. The addition of oxygen to the feed inlet enhanced conversion efficiency substantially; probably, it favors the re-oxidation of carbonaceous residues formed over the catalyst surfaces, avoiding the catalyst deactivation and hence promoting catalyst stability.
Keywords: GTL Process; Synthesis Gas; 10Ni-2La/γ-Al2O3 ; Catalysis; Hot Spot; ATR

The biosorption characteristics of copper(II) ions using Posidonia oceanica biomass were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, biosorbent dosage and temperature were studied. The equilibrium data were applied to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model fitted very well the equilibrium data, and the maximum uptake of Cu(II) by Posidonia oceanica was found to be 76.92 mg/g. The mean free energy E (10.78 kJ/mol) from the D-R isotherm indicated a chemical ion-exchange mechanism. Kinetic results showed that the pseudo-second-order kinetic model was well fitted to the experimental data. Thermodynamic parameters depicted the exothermic nature of biosorption and the process was feasible and spontaneous. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Cu(II) ions.
Keywords: Posidonia oceanica ; Biosorption; Thermodynamic Studies; Kinetic; FTIR; Desorption

Removal of cesium ion in aqueous solution using immobilized sericite beads by Choong Jeon; Jong-Oh Kim; Seung-Mok Lee (1219-1224).
To apply sericite effectively in the adsorption process, it was immobilized by entrapment method using sodium alginate. Since the immobilized sericite beads have excellent mechanical strength and swelling characteristics, channeling of flow and the increase of pressure drop were not observed through column operations. In addition, it was also stable under pH 10 and 45 °C of cesium solution. The maximum adsorption capacity and Langmuir adsorption constant was 1.430mg/g and 2.329 L/mg, respectively, at initial pH 5 of cesium solution in batch type and the Langmuir model with higher correlation coefficient of 0.997 fits experimental data better than Freundlich model. The breakthrough point emerged around 15 (1.0 mL/min) and 20 bed volumes (0.5 mL/min), and the cesium ions bound to the immobilized sericite beads were readily released and quantitatively recovered by a few bed volumes of 1.0M of HNO3 solution. Furthermore, bed volumes of cesium ions for firstly reused sericite beads can be still maintained as 18, which shows good regeneration ability.
Keywords: Sericite; Cesium Ion; Adsorption; Packed-bed Column; Immobilization

Candida antarctica lipase was covalently immobilized onto the surface of cellulose acetate-coated Fe2O3 nanoparticles. The characterizations of immobilized lipase were examined by Fourier transform infrared spectrophotometer (FTIR) and field emission gun-scanning electron microscopy (FEG-SEM). The immobilized lipase was assayed for production of monoglycerides (MG) and diglycerides (DG) by glycerolysis of olive oil in a solvent medium. The effect of various reaction conditions on the MG and DG production such as reaction time, temperature, the molar ratio of glycerol to oil and amount of immobilized lipase was investigated. The optimum condition for MG and DG production was found at 50 °C temperature and 0.025 g of lipase with the molar ratio of glycerol to oil 1.5: 1 in 5 h of reaction time. The effect of substrate concentration on enzymatic activity of the free and immobilized lipase showed the best fits to the Lineweaver-Burk plots. The K m and V max values of immobilized lipase were found to be 25mM and 0.58mM/min, whereas that for free lipase was 52.63mM and 1.75mM/min, respectively. The activation and deactivation energy was found to decrease for immobilization of lipase on cellulose acetate-coated Fe2O3 nanoparticles.
Keywords: Immobilization; Candida antarctica Lipase; Glycerolysis; Monoglycerides; Diglycerides

Effect of shear stress on the growth of continuous culture of Synechocystis PCC 6803 in a flat-panel photobioreactor by Min-Gyu Sung; Won-Sub Shin; Woong Kim; Jong-Hee Kwon; Ji-Won Yang (1233-1236).
The effect of hydrodynamic forces generated by air bubbles on cell growth of continuous culture of Synechocystis PCC 6803 was studied in a flat-panel photobioreactor. Keeping all relevant parameters constant enables the optimization of individual parameters, for which a continuous cultivation approach has significant advantages. Continuous culture of Synechocystis PCC 6803 was cultivated under different gas velocities from 0.022 m s−1 up to 0.128 m s−1. Based on direct determination of effective growth rate at constant cell densities, cell damage due to shear stress induced by the increasing gas velocity at the sparger was directly observed. A significant decrease of effective growth rate was observed at gas velocity of 0.085 m s−1 generated at the gas flow rate of 200 ml min−1, indicating cell damage by shear stress. Optimization of gas volume and the development of an effective aeration system corresponding to a given reactor setup is important to realize a reliable cell growth.
Keywords: Shear Stress; Bioprocess Optimization; Gas Flow Rate; Continuous Cultivation; Photobioreactor

Impact of speciation on CO2 capture performance using blended absorbent containing ammonia, triethanolamine and 2-amino-2-methyl-1-propanol by Hao-Yang Song; Soo-Bin Jeon; Se-Yong Jang; Sang-Sup Lee; Seong-Kuy Kang; Kwang-Joong Oh (1237-1245).
In our previous study, a high CO2 absorption rate was achieved using a blended absorbent containing AMP, NH3, and TEA. The species of the blended absorbent was determined in this study using 13C nuclear magnetic resonance (NMR) spectroscopy and a modified Kent-Eisenberg model. The carbamate formation constant was also regressed using the model. Bicarbonate and carbonate ions decrease the absorption efficiency and have a positive effect on CO2 stripping. Carbamate has a negative effect on regeneration; a regeneration temperature of 373 K minimized the energy needed. In conclusion, the prediction equation and NMR analysis provide an easy way of determining carbonate group species and carbamate species concentrations, and this method will be helpful in optimizing CO2 capture with blended absorbents.
Keywords: Blended Absorbents; Modified Kent-Eisenberg Model; Speciation; NMR; Absorption and Regeneration Efficiency

Our aim is to improve the predictions for the viscosities of selected light liquid hydrocarbon mixtures by using a reliable model based on Peng-Robinson equation of state (PR EOS). Therefore, a viscosity model on the basis of the similarity between PvT and Tμ(viscosity) P has been applied. Based on the volume-translated Peng-Robinson equation of state (VTPR EOS), a correction has been used for viscosity to improve the results of model. The viscosity model can be extended to mixtures by using an appropriate mixing rule for the parameters of the PR model. For a better description of viscosity and improvement of some calculation results, a mixing rule has been proposed for the parameters of the model. The results of the model show that the agreement between experimental and the calculated viscosities is reasonably good and noticeable improvements can be seen in the results of some calculations.
Keywords: Viscosity; Equation of State; PRμ Model; Hydrocarbon Mixtures

Experimental measurement and modeling of saturated reservoir oil viscosity by Abdolhossein Hemmati-Sarapardeh; Seyed-Mohammad-Javad Majidi; Behnam Mahmoudi; Ahmad Ramazani S. A; Amir H. Mohammadi (1253-1264).
A novel mathematical-based approach is proposed to develop reliable models for prediction of saturated crude oil viscosity in a wide range of PVT properties. A new soft computing approach, namely least square support vector machine modeling optimized with coupled simulated annealing optimization technique, is proposed. Six models have been developed to predict saturated oil viscosity, which are designed in such a way that could predict saturated oil viscosity with every available PVT parameter. The constructed models are evaluated by carrying out extensive experimental saturated crude oil viscosity data from Iranian oil reservoirs, which were measured using a “Rolling Ball viscometer.” To evaluate the performance and accuracy of these models, statistical and graphical error analyses were used simultaneously. The obtained results demonstrated that the proposed models are more robust, reliable and efficient than existing techniques for prediction of saturated crude oil viscosity.
Keywords: Viscosity; Experimental Data; LSSVM; Model; Oil; Petroleum

Few-layered graphene oxides (GOs) were successfully synthesized from graphite using Hummers’ method. The synthesized GOs were characterized in detail by SEM, AFM, XRD, and FTIR spectroscopy. The prepared GOs were used as adsorbents to preconcentrate Pb(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength and temperature on the removal of Pb(II) ions from solution to GOs were investigated. The sorption of Pb(II) on GOs was dependent on pH values and independent of ionic strength, which suggested that Pb(II) sorption on GOs was mainly dominated by strong inner-sphere surface complexation. The maximum adsorption capacities (C smax ) of Pb(II) on GOs were calculated to be 344 mg/g at 293 K, 487 mg/g at 308 K, and 758mg/g at 333 K, respectively. The C smax values are the highest sorption capacities of today’s materials for the sorption of Pb(II) ions from aqueous solutions. The thermodynamic parameters were calculated from the temperature-dependent sorption isotherms, and the results indicated that Pb(II) sorption on GOs was spontaneous and endothermic. The results suggested that the GOs were promising materials for the preconcentration of Pb(II) and other kinds of heavy metal ions from aqueous solutions in environmental pollution cleanup in real work.
Keywords: Graphene Oxides; Pb(II) Ions; Sorption; Thermodynamic Parameter; Interaction Mechanism

Effects of cobalt and cobalt oxide buffer layers on nucleation and growth of hot filament chemical vapor deposition diamond films on silicon (100) by Mushtaq Ahmad Dar; Hatem Abuhimd; Iftikhar Ahmad; Mohammad Islam; Mohammad Rezaul Karim; Hyung-Shik Shin (1271-1275).
An initial study on the nucleation and growth of diamond, using hot filament chemical vapor deposition (HFCVD) technique, was carried out on Co and CoO thin buffer layers on non-carbon substrates (Si (100)), and the results were compared with conventional scratching method. The substrate temperature during the growth was maintained at 750±50 °C. A mixture of CH4 and H2 (1: 100 volume %) was used for deposition. The total pressure during the two hour deposition was 30±2 Torr. X-ray photoelectron spectroscopy (XPS) study showed the diamond nucleation at different time periods on the Co and CoO seed layers. It is observed that Co helps in nucleation of diamond even though it is known to degrade the quality of diamond film on W-C substrate. The reason for improvement in our study is attributed to (i) the low content of Co (~0.01%) compared to W-C substrate (~5–6%), (ii) formation of CoSi2 phase at elevated temperature, which might work as nucleation sites for diamond. SEM analysis reveals a change in the morphology of diamond film grown on cobalt oxide and a significant reduction in the size of densely packed crystallites. Raman spectroscopic analysis further suggests an improvement in the quality of the film grown on CoO buffer layer.
Keywords: Hot Filament Chemical Vapor Deposition (HFCVD); CVD Diamond; Cobalt; Cobalt Oxide; Filament-substrate Distance

A novel method of producing ursodeoxycholic acid was developed through direct electro-reduction of 7-ketolithocholic acid in a divided electrolytic cell. Titanium ruthenium mesh electrode was used as the anode, while high purity lead plate was used as the cathode. The process was optimized with regards to the electrolyte, temperature, concentration of methanol, current density and concentration of anolyte. When potassium bromide was used as the electrolyte, the saturated solution of 7-ketolithocholic acid in 85–93% (v/v) methanol, current density 9.52–28.6 A/m2 and concentration of anolyte at 4–6% (w/w), the maximum percentage yield of ursodeoxycholic acid could be 47%. The method will provide a potential approach for large-scale production of ursodeoxycholic acid.
Keywords: 7-Ketolithocholic Acid; Chenodeoxycholic Acid; Ursodeoxycholic Acid; Direct Electroreduction; Potassium Bromide

Functional polyurethane surfactants (tri-block) were synthesized by addition polymerization of hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI) and 2, 4-toluene diisocyanate (TDI) with poly (propylene oxide) (PPO) and monoallyl-end-capped poly (ethylene oxide) (PEO). The chemical structure of the polyurethane surfactants (PUS) was confirmed by Fourier transform infrared, 1H NMR and 13C NMR spectroscopy. Then, a series of polyvinyl acetate (PVAc) latexes were successfully synthesized by the emulsion copolymerization in the presence of different PUS. The particle size, amount of coagulum and surface tension were evaluated. These polymeric surfactants were found to have excellent surface activity. The lowest surface tension of polyurethane surfactant aqueous solutions could be reduced to 41.5 dyn/cm for IPDI. All the polyurethane surfactants synthesized had low critical micelle concentrations and could reduce the surface tension even at very low concentration levels (10−3–10−2 molL−1).
Keywords: Polymeric Surfactants; Surface Tension; Polyurethane; Emulsion Copolymers