bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extraction equilibria of lead(II) from nitrate solutions with acidic organophosphorus compounds
Authors: Juang Ruey‐Shin , Lee Shwu‐Hwa 
Published: May 2005

AbstractThe distribution data were numerically analyzed for the extraction of trace lead(II) from 1·0 mol dm−3 (Li,H)NO3 media with toluene solutions of acidic organophosphorus compounds (HR), including di(2‐ethylhexyl)phosphoric acid (D2EHPA) and 2‐ethylhexylphosphonic acid mono‐2‐ethylhexyl ester (HEHEHP). The complex formulations were determined to be \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm PbR}_2 {\rm (HR)}},{\rm }\overline {{\rm PbR}_2 {\rm (HR)}_4 },{\rm and }\overline {{\rm Pb(NO}_3 {\rm )R}} $\end{document} for the D2EHPA system and to be \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm PbR}_2 {\rm (HR)}_{\rm 3} },{\rm }\overline {{\rm PbR}_2 {\rm (HR)}_4 },{\rm and }\overline {{\rm Pb(NO}_3 {\rm )R(HR)}} $\end{document} for the HEHEHP system. In this work, the equilibrium constants for the formation of these complexes were also given at 298 K.
Selective hydrogenation of citral over PtSn supported on activated carbon
Authors: Neri Giovanni , Donato Andrea , Milone Candida , Mercadante Lucina , Visco A. Maria 
Published: May 2005

AbstractHydrogenation of citral has been studied over Pt and PtSn catalysts supported on activated carbon. Under the conditions used the unsaturated alcohols, geraniol and nerol, were the main reaction products. Addition of a small amount of tin (20% at.) to Pt/C increases the overall catalytic activity whereas a decrease is observed at higher tin contents. Addition of tin leads also to an increase in the selectivity to unsaturated alcohols which reaches a value of about 90%. The higher selectivity and activity are attributed to an activation of the CO bond by tin ions.
Kinetic modelling of methanation reaction over a CoMo/SiO2 catalyst
Authors: Chen Hong , Adesina Adesoji A. 
Published: May 2005

AbstractThe methanation kinetics of CO over a bimetallic catalyst containing 6Co:1 Mo:4K:100SiO2 has been studied and compared with that over a 6Co:4K:100SiO2 monometallic catalyst. Nine models arising from carbide, enolic and Eley–Rideal mechanisms were considered and assessed with respect to the rate data obtained for each catalyst. Interestingly, all three models which were considered statically adequate involved the dissociative adsorption of H2 as the rate‐determining‐step (RDS). The modelling results also suggest that the introduction of Mo to Co altered the methanation behaviour of CO over cobalt kinetically but not mechanistically.
Immobilization of chitinase on a reversibly soluble–insoluble polymer for chitin hydrolysis
Authors: Chen Jyh‐Ping , Chang Ko‐Chang 
Published: May 2005

AbstractSerratia marcescens chitinase was immobilized by covalent binding to a polymer (hydroxypropyl methylcellulose acetate succinate, AS‐L) showing reversibly soluble–insoluble characteristics with pH change. The immobilized enzyme (CHAS) was soluble above pH 5·2 and insoluble below 4·5, which offers advantages in that it can carry out hydrolysis of chitin particles in a soluble form yet be recovered after precipitation at low pH. CHAS has much higher activity than chitinase immobilized to a water‐insoluble carrier. The effects of pH and temperature on the activity and stability of CHAS, and the adsorption of CHAS to chitin were studied and compared with those of free chitinase. Following repeated pH cycles between 6·6 and 4·5, CHAS lost 30% of its enzyme activity during the first cycle due to protein release and enzyme denaturation, but substantially less activity was lost in the following cycles, with minimum enzyme denaturation. Chitin hydrolysis with CHAS could be carried out in a semi‐batch mode with intermittent enzyme precipitation and product removal, this can enhance product yield up to 1·4‐fold when compared with batch reaction.
Structural changes and surface properties of Cox Fe3—x O4 spinels
Authors: Said Abd El‐Aziz A. , Hassan Ehsan A. , El‐Awad Ahmed M. , Abd El‐Salaam Khalf‐Alla M. , Abd El‐Wahab Mohamed M. M. 
Published: May 2005

AbstractThe cobalt ferrite spinel oxide series, CoxFe3–xO4 (0 ≤ x ≤ 3), has been prepared by coprecipitation. The adsorption–desorption isotherms of all the compositions calcined between 200 and 600°C have been measured using nitrogen gas at −196°C. The structural and the phase changes were characterized by TGA and XRD techniques. The results obtained revealed that the transformation of γ‐ to α‐Fe2O3 was accompanied by a sharp decrease in the SBET values. The addition of Co2+ ions into Fe2O3 up to × = 0.6 led to an observable increase in the SBET value. This behaviour was attributed to the incorporation of Co2+ ions into the Fe2O3 lattice and the retardation of the phase transition of γ‐ to α‐Fe2O3. The minimum SBET values obtained at a lattice composition of × = 1·0 corresponded to the formation of a cobalt ferrite normal spinel which is associated with the existence of narrow pores. The increase in SBET values in the cobalt‐rich region, with a maximum at x = 2·6 is explained on the basis of the cationic replacement of Fe3+ ions in the Co3O4 lattice. Finally, calculation of pore volume distribution was carried out, in addition to Va–t plots, in order to study the nature of the surface porosity, which was found to be mesoporous.
Effects of the seed sludge on the performance of UASB reactors for treatment of toxic wastewater
Authors: Dangcong Peng , Xingwen Zhang , Qiting Jin , De Zhang , Liangkui Xiang 
Published: May 2005

AbstractA comparative study of different sludges (anaerobic sewage sludge and anaerobic sewage sludge cultivated for 30 days) as the seed of UASB reactors for treatment of synthetic resin production wastewater was carried out on a laboratory scale. Significant differences in reactor performance were observed. With anaerobic sewage sludge seed, the reactor obtained a 71% COD removal efficiency and produced 2·94 dm3biogas per dm3wastewater under an organic loading rate of 4·5 kg COD m−3day−1. The sludge in the reactor was diffuse and possessed poor settling ability, which led to effluent SS as high as 1200 mg dm−3. However, with anaerobic sewage sludge cultivated with synthetic substrate for 30 days as a seed, the same reactor gave 78% COD removal efficiency and produced 3·5 dm−3biogas per dm3wastewater at the same loading rate. Moreover, the sludge in the reactor was completely granulated and possessed good settling ability, which resulted in effluent SS as low as 200 mg dm−3. The granular sludge produced less biomass per gram COD removed than the diffused sludge. Anaerobic sewage sludge cultivated for a short time could form the nuclei of granules for the reactor, allowing granulation to proceed smoothly. Therefore, sludge nuclei are a prerequisite of sludge granulation in UASB reactors for treatment of toxic wastewater.
Effect of carrier ionic properties on cellulase productivity by immobilized filamentous Trichoderma reesei
Authors: Zhaoxin Lu , Kumakura Minoru 
Published: May 2005

AbstractFilamentous cells of Trichoderma reesei were immobilized by an adhesion method using carriers prepared by radition polymerization and the effects of the ionic properties of the carriers on cellulase productivity have been investigated. The cationic polymers were better than anionic polymers in the adhesion of the cells. Enzyme productivity was affected by the ionic property of the polymer, the concentration of the coating monomer and the hydrophobicity of the pre‐coating polymer.
Estimation of interfacial concentration of extractants from interfacial tension measurements
Authors: Prochaska Krystyna , Alejski K. , Szymanowski Jan 
Published: May 2005

AbstractThe use of the spline function, logarithmic polynomial, Szyszkowski and Temkin equations to estimate the extractant interfacial concentration are discussed. The distribution of the experimental data and its nonlinearity upon the approximation errors and the surface concentration are presented.The error of the interfacial tension isotherm estimation depends upon the equation considered. The Temkin isotherm deviates significantly from the experimental data. The distribution of experimental data affects both the matching of the interfacial tension isotherm with the logarithmic polynomial and the surface excess isotherm. The best approximations (low approximation errors and lack of sensitivity upon experimental data distribution) are obtained with the use of the Szyszkowski equation and the spline function.
Kinetics of horseradish peroxidase‐catalysed polymerization and precipitation of aqueous 4‐chlorophenol
Authors: Nicell James A. 
Published: May 2005

AbstractHydrogen‐peroxide oxidoreductase (EC 1.11.1.7) from horseradishes catalyzes the polymerization and precipitation of aromatic compounds from aqueous solutions in the presence of hydrogen peroxide. This process has demonstrated good potential as a technique for the removal of toxic contaminants from wastewaters. Steady‐state, fully transient and pseudo‐steady‐state models of the horseradish peroxidase system have been developed to assist in the under‐standing of the dominant mechanisms of inactivation and to aid in the selection and design of an appropriate reactor system. Model validation was performed by comparing model predictions with experimental observations of the polymerization and precipitation of 4‐chlorophenol. Good agreement was found between experimental data and predictions of the fully transient and pseudo‐steady‐state models. The pseudo‐steady‐state model has the advantage of reduced complexity with a corresponding reduction in computation time required to solve model equations while maintaining the predictive ability of the fully transient model.
Multifunctional viscosity index improvers
Authors: Mohamed Mohamed M. , Abou El Naga Hamdi H. , El Meneir Mohamed F. 
Published: May 2005

AbstractStyrene alkylmethacrylate succinimide phosphoric acid additives are synthesised and evaluated for use in multigrade crankcase lubricating oils as multifunctional viscosity index improvers having both antioxidant and dispersant properties. The synthesis is based on reacting styrene alkylmethacrylate (prepared by the reaction of styrene and 2‐ethylhexylmethacrylate at different styrene/methacrylate mole ratios under various reaction conditions) with maleic anhydride and tetraethylenepentamine in the presence of phosphoric acid. Comparative evaluation of the properties of the synthesised products (e.g., viscosity properties, shear stability, oxidation stability and dispersive power) with commercial additives showed they were suitable for use as viscosity index improvers.
Stability and proteolytic activity of papain in reverse micellar and aqueous media: A kinetic and spectroscopic study
Authors: Vicente Laura C. , Aires‐Barros Raquel , Empis José M. A. 
Published: May 2005

AbstractThe stability and proteolytic activity of papain were studied in reverse micellar systems, and in aqueous media. In reverse micelles the maximum activity obtained was 80% of the enzyme activity in aqueous solution. Higher papain stability was found in reverse micellar systems compared with that in aqueous solution with half‐lives of 24 and 10 days respectively. Electron spin resonance (ESR) spectroscopy studies of aqueous and reverse micellar systems were performed in an attempt to explain the observed enzyme stability and activity profiles. For this purpose a spin label—TEMPOacetamide—was covalently linked to the Cys‐25 residue of the papain active center. ESR spectra of labeled papain indicated that catalytic activity of papain could be related to the conformational rigidity near the reaction center. The lower activities obtained in reverse micelles could be a result of the greater degree of mobility and polarity observed in these systems, which can be attributed to papain unfolding. The greater stability found for papain in reverse micelles could be the result of the limited extent of this denaturing process owing to the organized surfactant molecules around the enzyme.
Catalysis by intermetallic compounds III. The hydrogenation of buta‐1,3‐diene catalysed by cePd3–xAux alloys
Authors: Bahia Amrik , Harris I. Rex , Winterbottom John M. 
Published: May 2005

AbstractThe intermetallic alloy series CePd3–x Aux (0 ≤ x ≤ 1) has been prepared from its constituent elements by carbon arc melting and employed as catalysts for the hydrogenation of buta‐1,3‐diene at 1 bar (101·5 kPa) total pressure in the temperature range 50–120°C. Selectivities for butene formation and initial butene distributions were very similar to those measured for CePd3 and Pd‐rich CePd3–x Pdx alloys. Activity measurements showed that CePd2Au, was about three times more active than CePd3 despite having a surface which was shown by Auger electron spectroscopy (AES) to be deficient in Pd compared with the bulk and also compared with CePd3. Although a relationship appears to exist between catalyst activity and bulk electronic properties it can be only fortuitous and the surface electronic structure must be the important factor especially in view of the palladium‐deficient surface.
Heavy metals in the environment Part III. Anion exchange properties of poly‐4‐vinyl pyridine from acid chloride solutions
Authors: Chaudhary Abdul J. , Donaldson John D. , Grimes Susan M. , Boddington Stephen C. 
Published: May 2005

AbstractThe metal extractive properties of poly‐4‐vinyl pyridine, prepared in the free base form, were studied for Cu2+, Ni2+, Co2+, Zn2+ and Cd2+ in chloride solutions. The efficiency of metal extraction depended on the pH and composition of the solutions. For maximum metal extraction, the optimum initial pH of the solution was found to be within the range of 0·8 to 1·2 for WR/V ratios of 45 000–50 000 mg dm−3. The metal extractive power of the resin was found to increase as the metal chloride concentration of the solution was increased. A similar effect was found with all resin‐active metals when experiments were carried out in solutions containing high concentrations of KCl.
Biotreatment of coals and coal‐related compounds by hydrogen‐utilizing microorganisms
Authors: Murty Mangena V. S. , Aleem Muhammad I. H. , Kermode Richard I. , Bhattacharyya Dibakar 
Published: May 2005

AbstractDesulfovibrio desulfuricans and Acidianus brierleyi were used to study hydrogenation of coal, pretreated coal, asphaltenes, and model compounds [diphenyl methane (DPM) and fumarate] under anaerobic conditions. This study involved three primary aspects: (1) determination of net hydrogen‐uptake, (2) identification of the biohydrogenated product of fumarate, and (3) testing the influence of hydrogen uptake/biohydrogenation of coal in terms of direct liquefaction yield. The net hydrogen uptake values (from Warburg and GC assays) by the coals or the model compounds (controls) were less than that of the biotreated samples. The greated hydrogen uptake (net, 1878 μmol g−1; coal control, 245; cell control, 127) occurred in untreated coal KCER No. 4677 in the presence of D. desulfuricans. The net hydrogen uptake by coals varied depending upon the coal type and the microorganism. Model compound DPM showed its highest hydrogen uptake rate when catalysed by D. desulfuricans (150 μmol g−1 h−1). D. desulfuricans also hydrogenated 36% of the fumarate to succinate in the presence of hydrogen.Biotrated coal KCER No. 4677 (with 1878 μmol H2 g−1) was subsequently subjected to direct liquefaction. It showed a net increase in liquefaction yield of 5·4% as a result of the biotreament.
Characterization of activated carbon produced from almond shell and hazelnut shell
Authors: Balci Suna , Doǧu Timur , Yücel Hayrettin 
Published: May 2005

AbstractAmmonium chloride‐impregnated and untreated almond shell and hazelnut shell samples were carbonized in a flow of nitrogen at relatively low temperatures. Pore structure characterization and sorption capacities of activated carbons prepared from shells of almond and hazelnut indicated that treatment with NH4Cl increased the total surface area and improved sorption characteristics. Chemical activation carried out at 350°C gave products with surface area values above 500 m2 g−1. On the other hand, the surface area values observed for the products obtained from untreated raw materials were about half of this value. The surface area of products obtained from NH4Cl‐impregnated samples reached values of over 700 m2 g−1 when the carbonization temperature was increased 700°C.
Kinetics of lactose isomerisation to lactulose in an alkaline medium
Authors: Dendene Kamel , Guihard Laurence , Nicolas Stéphane , Bariou Bernard 
Published: May 2005

AbstractThe aim of this work was to determine easily and quickly the operating conditions for the industrial production of lactulose (rate of isomerisation, rate of lactose degradation, reaction time, temperature, pH). The kinetic equations of lactulose formation and lactose degradation in an alkaline medium (NaOH) were determined. Experiments were carried out at different OH− concentrations (0·5 × 10−2–19 × 10−2 mol dm−3) and at different temperatures (328–353 K). A kinetic model is presented which can be used to describe the experimental results and hence a procedure for industrial production.
Metformin‐selective PVC membrane electrode based on metforminium phosphomolybdate ion pair
Authors: Rizk Mahmoud S. 
Published: May 2005

AbstractThe (1:1) (phosphomolybdate:metformin) ion pair is used as the ion exchanger in preparing conventional plastic membrane electrodes for metformin (Mf) and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide concentration range. The calibration graph slope was constant at 57 mV per concentration decade at 25°C for up to 5 days with continuous soaking. Then the slope decreased as the time of soaking increased, reaching 42 mV decade−1 after 20 days. The changes in pH did not affect the electrode performance within the range 3.0–10.5. The standard electrode potentials were determined at different temperatures and were used to calculate the isothermal coefficient of the electrode (0.000695 V °C−1). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Mf in pure solutions and in pharmaceutical preparations.
A flow injection system for simultaneous determination of starch and glucose concentrations
Authors: Umoh Enobong F. , Schügerl Karl 
Published: May 2005

AbstractA flow injection analysis (FIA) system capable of simultaneously determining the concentrations of starch and glucose in samples was set up. The system consisted of glucoamylase (GA), glucose oxidase (GOD), (EC 1.1.3.4) and mutarotase (MUT, EC 5.1.3.3) immobilized on macroporous polymer packed in reaction cartridges was operated at 30°C. Glucose resulting from the action of glycoamylase or originally present in the samples was determined amperometrically. The starch was analysed with the system without needing prehydrolysis with α‐amylase, and inclusion of mutarotase was found necessary only when the sample originally contained α‐glucose. A linear detection range up to 1.5 g dm−3 and 4.0 g dm−3 was obtained for the streams from which glucose and total sugar concentrations were measured, respectively. The system was able to analyse up to 10 samples per hour.
Comparison of the catalysed decomposition of hydrogen peroxide over superconducting and insulating barium cuprates—kinetics of decomposition over Y2BaCuO5
Authors: Khalil Laila B. , Mourad Wedad E. , Rophael Magdy W. 
Published: May 2005

AbstractCatalytic activities of two non‐conducting cuprates (Ba2Cu3O5, Y2BaCuO5) and a superconducting cuprate YBa2Cu3O7–δ, prepared by two different methods, were compared using H2O2 solution. The two non‐conducting barium cuprates were found to be about two orders of magnitude more active than the superconducting perovskite‐like YBa2Cu3O7–δ. The near coincidence of the kinetic curves for the catalysed decomposition of H2O2 over YBa2Cu3O7–δ, prepared either from the perovskite‐like Ba2Cu3O5 and Y2O3 or from its components, proves that Ba2Cu3O5 is essential in the formation of YBa2Cu3O7–δ. First‐order kinetics were observed for the catalysed decomposition of H2O2 solution over the non‐perovskite Y2BaCuO5 at the initial stages of the reaction, similar to that of the superconducting perovskite catalyst. A tentative scheme of the possible catalytic reactions for the decomposition of H2O2 solution over the insulator Y2BaCuO5 is given.
Adsorption of chlorophyll‐a from acetone solution on natural and activated bentonite
Authors: Pradas E. González , Sánchez M. Villafranca , Viciana M. Socías , Campo A. Gallego 
Published: May 2005

AbstractThe adsorption of chlorophyll‐a on bentonite desiccated at 110°C, untreated and acid‐treated with H2SO4 solutions over a concentration range between 0·25 and 2·50 mol dm−3, from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm−3 H2SO4‐treated sample), type H (0·50 mol dm−3 H2SO4‐treated sample) and type L (1·00 and 2·50 mol dm−3 H2SO4‐treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll‐a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (Kf) of the samples; Kf values range from 0·43 mg kg−1 for the untreated bentonite up to 108·89 mg kg−1 for the 0·50 M H2SO4‐treated bentonite. The removal efficiencies (R) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H2SO4‐treated bentonite.
Efficient fuzzy control strategies for the application of pH‐stat to fed‐batch cultivation of genetically engineered Escherichia coli
Authors: Jin Sha , Ye Kaiming , Shimizu Kazuyuki 
Published: May 2005

AbstractIn the cultivation of genetically engineered Escherichia coli it is very important to control the substrate concentration at an appropriate level in order to avoid the accumulation of acetate, thereby elevating the expression level of plasmid‐encoded protein. In this paper, a pH‐stat mode of fuzzy control was considered for the overexpression of β‐galactosidase in the fed‐batch cultivation of recombinant E. coli. In the simple pH‐stat fuzzy control, the response of pH change in the culture broth to the feeding rate of glucose was used to estimate the glucose consumption rate. In the modified pH‐stat fuzzy control, the glucose consumption rate was accurately estimated by using pH change and the change in the carbon dioxide content of the exhaust gas. With this control strategy, the cell density could be increased to 72 g DCW dm−3, which was twofold higher than that attained in the cultivation with the simple pH‐stat fuzzy control. The bulk β‐galactosidase concentration was increased to 4150 U cm−3, which was threefold higher than when the simple pH‐stat control was used.
Comparative sorption equilibrium studies of toxic phenols on flyash and impregnated flyash
Authors: Singh Binay Kr. , Rawat Narendra S. 
Published: May 2005

AbstractIn the present study, the sorption of toxic phenols, which include phenol, o‐cresol, m‐cresol, p‐cresol, o‐nitrophenol, m‐nitrophenol and p‐nitrophenol, has been investigated. The influences of various factors, such as particle size, impregnation of flyash (IFA), pH and temperature on the sorption capacity have been studied. Equilibrium modelling has been carried out using Langmuir and Freundlich isotherm equations and constants have been calculated under different conditions. Thermodynamic studies have also been carried out and values of standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) calculated.