Volume 9, No. 1 (2008)
Articles
STUDY OF THE METHYLCYCLOHEXANE OPENING CYCLE REACTION ON MOLYBDENUM AND TUNGSTEN OXIDES ETUDE DE LA REACTION D’OUVERTURE DE CYCLE DU METHYLCYCLOHEXANE SUR LES OXYDES DE MOLYBDENE ET DE TUNGSTENE
AMEL DJEDDI*, YU LIU, IOANA FECHETE, FRANÇOIS GARIN
Hydrogenolysis of methylcyclohexane was studied over molybdenum and tungsten di-tri oxides. The products obtained were 2 methylhexane, 3-methylhexane and n-heptane and dimethylpentanes (DMPs). The oxides were characterized before and after reduction by XRD, N2 sorption and SEM. Molybdenum oxides were reduced 12 h at 400 °C while tungsten oxides at 500 °C. We noticed that selectivity to ring opening on molybdenum oxides is minority, while the isomerization to dimethylcyclopentanes and ethylcyclopentane is the main reaction. On the tungsten oxides, the ring opening reaction occurred with the formation of DMPs although the isomerization, the aromatization and the cracking reactions are dominant.
REGIOSELECTIVE FUNCTIONALIZATION OF IMIDAZOAZINES AND DEVELOPMENT OF INDIRECT C-ARYLATION REACTION, TOOLS OF CHOICE TO PREPARE VARIOUS DI- AND TRISUBSTITUTED COMPOUNDS FONCTIONNALISATION REGIOSELECTIVE D’IMIDAZOAZINES, ET DEVELOPPEMENT DE LA REACTION DE C
AHMED EL AKKAOUI(1), (2), JAMAL KOUBACHI(1), (2), SABINE BERTEINA-RABOIN(1)*, ABDERRAHIM MOUADDIB(2), GÉRALD GUILLAUMET(1)
Electrochemical and in situ AFM studies of cadmium electrodeposition from an aqueous 0.1 M CdSO4 solution have been carried out in the case of (100) n-type silicon single crystal. The mechanisms related to the initial stages of the nucleation and growth mechanism of cadmium have been studied as a function of different potential steps. Within appropriate potential ranges the initial deposition kinetics corresponded to a model including progressive nucleation and diffusion controlled cluster growth. Nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients at different overpotentials. A Ncrit-value of 14 ± 1 atoms was determined in the following potential range: –9 mV = ? = –11 mV. The response of the system at different waiting times at the equilibrium potential was also investigated.
PRELIMINARY STUDY ON A BIOTOLERABLE TERNARY SYSTEM, ACTING AS REDOX INITIATOR
STELIAN S. MAIER*, VASILICA MAIER, MELINDA PRUNEANU
This paper studies radical initiation of the crosslinking process within a model mixture of 19: 1 acrylamide: N,N’-methylene-bis-acrylamide, carried out at low temperature (below 6 °C), using a ternary initiator mixture containing hydrogen peroxyde (H2O2) as oxidizing agent, ascorbic acid (AA) as activating agent and uric acid (UA) as promoter and modulator of the radical centers development. The initiator system contains only biotolerable components and can be used for the obtaining of crosslinked protein molecular composites hydrogels, containing in-situ generated oligomers, able to be used in tissue engineering. The study establishes (i) the optimal composition of the initiator mixture (H2O2: AA: UA molar ratio of 1: 1: 0.1), (ii) the monomer: initiator mixture molar ratio (1: 0.021) and (iii) the lowest feasible concentration of H2O2 that simultaneously determines maximal hydrogel consistency and minimal volume of water extracted by syneresis. The hydrogel consistency was modeled using a mixture experimental design.
APPLICATIONS OF ARTIFICIAL INTELLIGENCE METHODS IN MACROMOLECULAR CHEMISTRY - COMPUTER-AIDED MOLECULAR DESIGN
TEODORA RUSU(1)*, HUGH CARTWRIGHT(2)
This paper describes the implementation of the Tabu Search (TS) algorithm in concert with the Computer-Aided Molecular Design (CAMD) scheme. Although other optimization approaches have been applied to CAMD with properties predicted using group contribution techniques, the TS algorithm implemented with novel neighbor-generating operators and combined with property prediction via connectivity index-based correlations provides a powerful technique for generating lists of near-optimal molecular candidates for a given application. In addition, the tabu lists help TS search the solution space both in a diversified way, to cover the entire search space, and in an intensified manner, to locate the final solution precisely. Moreover, TS is able to locate a large number of near optimal solutions within a short time.
NEURAL NETWORK BASED MODELING OF NOX DETECTION WITH A SENSOR – POLYMER SYSTEM
CIPRIAN PIULEAC(1), SILVIA CURTEANU(1)*, GABRIELA TELIPAN(2), MARIA CAZACU(3)
Some types of synthetic polymers have been tested in nitric oxide sensing. Feed-forward neural networks with different types and topologies are used in mathematical modeling of the system, to predict the voltage of the sensor as function of polymer type, gas concentration and time. In this way, the efficiency of the sensor can be appreciated. The relative errors, extremely low, obtaining in the validation phase, prove the validity of the neural models. The optimization problem performed by inverse neural network modeling answers the question what are the initial conditions that lead to an imposed value for output signal of the sensor.
OPTIMIZATION OF HOMOGENOUS OXIDATION PROCESS WITH HYGROGEN PEROXIDE USING BOX METHOD APPLIED FOR WASTEWATERS CONTAINING METHYLENE BLUE DYE?
CARMEN ZAHARIA*, DANIELA SUTEU
Delivery of textile or chemical wastewaters in river streams or pipeworks without an adequate treatment determines undesired consequences. Moreover, most dyes used nowadays are refractory compounds. Conventional biological treatments are not effective for most of synthetic dyes especially due to their polyaromatic structure. That is why advanced oxidation processes (e.g., H2O2/Fe2+) for decomposition of non-biodegradable organic contaminants into industrial effluents are attractive alternatives to conventional treatment. The paper proposes the study of homogenous oxidation (Fenton reagent) with hydrogen peroxide applied for some wastewaters containing Methylene Blue dye in different operational conditions in order to get the maximum decolourization removal using the empirical Box method. All kinetic experiments were performed on wastewater samples of 100 mL (100 mg dye/L) under continuing agitation, at a temperature of 17 ?C, pH of 6.5 and different concentrations (or volumes) of H2O2 and FeSO4 solutions. The methodology of the empirical Box procedure is experimentally applied and permitted to get the optimal values at pH = 6.5 for decolourization degree (92 %) that corresponds to 7.9 mL FeSO4 (stock FeSO4 concentration of 17.67 mmol Fe.L-1) and 1.18 mL H2O2 (stock H2O2 concentration of 8.235 mmol.L-1).
EFFECT OF THE PRESENCE OF CO-IONS ON THE KINETICS OF BIOSORPTION OF CADMIUM FROM AQUEOUS SOLUTIONS BY SOLID ACTIVATED SLUDGE: EXPERIMENTAL STUDY AND MODELING EFFET DE LA PRESENCE DE CO-IONS SUR LA CINETIQUE DE BIOSORPTION DU CADMIUM EN SOLUTION AQUEUSE PA
HOUCINE BENAISSA*, MOHAMED-AMINE ELOUCHDI
Our previous work has shown that dried activated sludge has the aptitude to remove important quantities of cadmium ions from simple synthetic aqueous solutions. In continuation, the present study describes the results of the experimental investigation and modelling of the influence of the different co-ions presence such as: cations (Na+, K+ and Ca2+) and anions (Cl-, SO42- and CO32-), at various initial concentrations, on cadmium biosorption kinetics by dried activated sludge, in batch conditions at 25 °C and natural initial pH of solution. The choice of these ions has been made because of their permanent presence in industrial wastewaters. As results obtained, the presence of these co-ions in solution was found to inhibit the uptake of cadmium by dried activated sludge at different degrees. Na+ and Cl- ions have no significant/weak effect. For K+, Ca2+, SO42- and CO32- ions, the effects ranged from an inhibition of cadmium by K+, CO32- and SO42- ions to a weak inhibition by Ca2+ ions. The results also showed that the kinetics of biosorption of cadmium by dried activated sludge was described by a pseudo-second order rate model.
CADMIUM AND NICKEL REMOVAL FROM WASTEWATER USING MODIFIED FLY ASH: THERMODYNAMIC AND KINETIC STUDY
MARIA VISA(1), (2), ANCA DUTA(1)*
The fly ash surface properties depend on many factors, including the coal composition, the burning process and the furnace characteristics. Developing an up-scalable process requires reproducible surface properties, less (or no) related to the above mentioned influences that can be obtained by tailoring the fly ash surface. The study presents the results obtained in Cd2+ and Ni2+ removal, using fly ash from CHP Brasov (Romania) with modified surface, prepared by long contact with alkaline solutions (NaOH 1N, 2N, 4N) and complexion agents (Complexone III, Pyrocatechol Violet). The immobilization efficiency is discussed in connection with contact time, wastewater volume: adsorbent mass ratio and ions concentration; Langmuir and Freundlich mechanisms were found to describe the adsorption processes. The process follows a pseudo-second order kinetic, for both metals, on the entire concentration range. Highly efficient adsorption, even at very low heavy metals concentrations (20 ppm), is registered for fly ash modified with NaOH.
INVESTIGATION OF THE HEAVY METALS CONTENT OF SOME FOOD PRODUCTS BY USING ATOMIC ABSORPTION SPECTROMETRY•
MAGDALENA MITITELU(1)*, FLORICA NICOLESCU2, CORINA IONITA(1), ANA BANCESCU(3), ELENA DOGARU(1), LUCIAN HÎNCU(4)
The content of some heavy metals (Cd, Pb, Cu and Zn) in some food products – beef, milk, and cheese – obtained from a rural farm located in Voroveni, Arges, Romania has been investigated. At the same time, parallel investigations were done on samples of grassland soil. Atomic absorption spectrometry (GBC-Avanta) has been used to determinate the concentration of heavy metals: Cd (? = 228.8), Cu (? = 324.7), Zn (? = 213.9), Pb (? = 217 nm). It has been observed that the concentration of these heavy metals exceeds the accepted limit values, both in food and soil.
MODELING AND OPTIMIZATION OF THE MILK FERMENTATION PROCESS USING Mg Al-CO3 HYDROTALCITE BY FACTORIAL ANALYSIS MODELISATION ET OPTIMISATION DE PROCESSUS DE FERMENTATION DE LAIT UTILISANT Mg Al–CO3 D’HYDROTALCITE PAR ANALYSE FACTORIELLE
ALISA VASILICA ARUS(1)*, GHEORGHITA JINESCU(2), ILEANA DENISA NISTOR(1), ALINA – VIOLETA URSU(1)
In this research work the main objective was studying the use of kn type factorial programs for modeling and optimization of the milk fermentation process in the presence of hydrotalcite. The milk fermentation is considered the principal phase in yoghourt technology. The yoghourt is a product resulted from the fermentation of the lactic acid under the action of two specific lactic bacteria: Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Using the experiment programming method, the mathematical model that corresponds to the answer function (the yoghourt acidity) is obtained, allowing simulation individual or interacting effects between parameters. According to the experimental program, which was used, and the variation of parameters interval, the real optimal values of parameters can be obtained, in the initial field or not.
IMPROVING THE BROWN FLOUR QUALITY ON THE ACCOUNT OF THE RHEOLOGICAL DETERMINATIONS OBTAINED IN THE ALVEOGRAPH, RHEOFERMENTOGRAPH AND MIXOLAB•
IULIANA BANU(1)*, GEORGETA STOENESCU(2), VIOLETA IONESCU(2)
The aim of the paper was to optimize the quality of the brown flour by grinding wheat at industrial level. The brown flour was obtained in intermediary extraction, besides the white flour. We have rheologically analyzed more variants of composition of the flour varieties. The optimization of the brown flour quality was made by recomposing the two flour varieties, white and brown, but also through the use of hemicellulases, a-amylases, cysteine. As the brown flour presented initially a high initial P/L report, and low energy, we proceeded to redistribute the flour fractions between the two types so that the mentioned rheological indices could be brought to the parameters closest to technological optimal standard. Between additivation, we could obtain, for the brown flour, those rheological parameters in the curves registered in the Mixolab, Alveograph and Rheofermentograph that are supposed to be optimal for getting high quality bread making products.
PREDICTION MODEL FOR THE RHEOLOGICAL BEHAVIOR OF COMPLEX EMULSIONS CONTAINING SOYBEAN OIL WITH VARIABLE CONTENTS OF PHOSPHOLIPIDES AND WATER MODELE DE PREDICTION DU COMPORTEMENT RHEOLOGIQUE POUR DES EMULSIONS COMPLEXES A BASE D’HUILE DE SOJA AVEC UN CONTE
I. VINTILA(1)*, A. GAVRUS(2), C. VIZIREANU(1), P. ALEXE(1)
The present paper research presents the validation of a mathematical model applied for the prediction of rheological behavior of the complex emulsions W/O type (water: 30%; crude, refined soybean oil: 70%). The rheological behavior was investigated for the emulsions realized with two types of industrial oils: S1-crude Soybean oil, S2-refined Soybean oil with different physical-chemical properties: 662 ppm phosphatides 0.14% moisture, FFA-index 0.73, solvent insoluble impurities content 0.17% for S1; 50 ppm phosphatides, FFA-index 0.019, 0.015% moisture, solvent insoluble impurities content 0.004% for S2. The mathematical model for the emulsions’ rheological behavior prediction was correlated with the composition of the complex emulsions W/O with crude and refined soybean oils. The parameters of the mathematical model were identified by the inverse analysis method based on the experimental rheological data values and was realized the validation of the theoretical mathematical model.
A STUDY ON THE BEHAVIOR OF A COMMERCIAL INVERTASE IN DIFFERENT ACTION CONDITIONS. INDUSTRIAL APPLICATIONS
MAGDA G. BRATU*, ALEXANDRU STOICA, LAVINIA BURULEANU, DANIELA AVRAM
This work presents the use of an enzymatic preparate based on invertase in the obtaining of invert sugar syrup. Sucrose syrup having various concentrations (70%; 75%; 80%) has been used as substrate. These concentrations were chosen in order to reduce the risk of a possible fermentation during experiments. The technological parameters which vary during the experiments are the pH of sucrose solution and the concentration of enzyme solution. It was observed that the optimal pH value for obtaining the maximal invert sugar quantity (when the substrate concentration and the enzyme adding level were maintained constant) was 4.5. It was noticed the fact that the optimal level of initial sucrose solution concentration for obtaining the maximal invert sugar quantity (when the pH value and the enzyme adding level were maintained constant) was 70%. Also, the optimal enzyme adding level (when the pH value and the substrate concentration were maintained constant) was 25 g / 3000 g sucrose.
INFLUENCE OF THE TECHNOLOGICAL PARAMETERS ON THE DRYING VELOCITY OF CRUMBLED FRUITS INFLUENCE DES PARAMÈTRES TECHNOLOGIQUES SUR LA VITESSE DE SÉCHAGE DES FRUITS ÉMIETTÉS
CRISTINA G. GRIGORAS*, LUCIAN GAVRILA
The fruits represent one of the basic products from humanely nourishment. Rich in sugars, vitamins, minerals substances, these contain also a considerable amount of water (75 – 92%) which drives to the existence of the favorable conditions for the development of the microorganisms responsible for the fruits degradation. Among the methods most used-up in order to reduce the water content of fruits is the preservation through drying. Although the drying involves a big consumption of energy, therefore a big cost, there is a simple method for removing this disadvantage: to increase the drying velocity. This paper presents the influence of the technological parameters (temperature of the drying air, drying time, dimension of the particles exhibited to drying) on drying velocity.
THE SOLUBILITY OF CARBON DIOXIDE IN AQUEOUS SOLUTIONS OF N-METHYLDIETHANOLAMINE (MDEA) AND TRIETHYLENE TETRAMINE (TETA). 1. EXPERIMENTAL LA SOLUBILITE DU CO2 DANS DES SOLUTIONS AQUEUSES DE N-METHYLDIETHANOLAMINE (MDEA) ET TRIETHYLENE TETRAMINE (TETA). 1.
JEAN-MARC AMANN, CHAKIB BOUALLOU*
CO2 solubility in a new solvent based on a blend of N-methyldiethanolamine (MDEA) and Triethylene Tetramine (TETA) was measured between 298 and 393 K for a MDEA concentration ranging from 1400 to 3400 mol•m-3 and a TETA concentration varying from 200 to 400 mol•m-3. At a given TETA concentration, a high increase in the MDEA concentration decreases the CO2 solubility in the solvent. Indeed, an increase in the amine concentration decreases the solubility. However, at a given MDEA concentration, an increase in the TETA concentration leads to a greater CO2 solubility. Affinity with CO2 is dominating compared to the reduction in solubility due to the increase in the TETA concentration. The presence of the TETA increases the CO2 solubility, particularly at low CO2 loading. But, at very low CO2 loadings, experimental uncertainties lead to lower CO2 solubility in the solvents than that obtained for MDEA aqueous solutions, whereas the presence of a very reactive amine with CO2 such as TETA should largely increase the solubility of this gas.