Volume 9, No. 3 (2008)
Articles
ELECTROCHEMICAL TREATMENT OF NITROPHENOLS CONTAINING WASTEWATERS TRAITEMENT ÉLECTROCHIMIQUE DES EAUX RÉSIDUELLES CONTENANT NITROPHENOLS
MIHAELA TERTIS, MARIA JITARU(*), MARIANA TOMA
There are two main objectives of this work: (a) to obtain fundamental data regarding the electrochemical behavior of some mononitrophenols [2-nitrophenol (2-NP), 3-nitrophenol (3-NP) and 4 nitrophenol (4-NP)] and dinitrophenols [2,4-dinitrophenol (2.4-DNP), 2,6 dinitrophenol (2,6-DNP)], influence of electrode nature, pH, concentrations on the electrochemical behavior and (b) to use these fundamental data (a) for the applied electrochemical reduction processes in order to reduce the nitrophenols concentration in synthetic wastewaters. We investigated both the wastewaters containing a single nitrophenol and a mixture of nitrophenols (4-NP and 2,6-DNP in different volume ratios), using different laboratory experimental plants: two compartment reactor type filter-press, an undivided electrochemical reactor and a two compartment reactor, all with electrolyte recirculation. The experimental processes were pursued by different methods: cyclic voltammetry (BAS100 and AUTOLAB PG-STAT12), and spectrophotometry in UV-Visible (Unicam Helyos B and DR/2000 HACH). The first peak potential, Ep1 for 2,6-DNP, shows two linear regions with different slopes, corresponding to an acid behavior specific to nitro phenols values (pKa = 4-5). The first peak height reaches the maximum value in acidic media. The applied electrolyses demonstrated practically 90-99% removal yield for the both nitro derivatives, depending on the experimental conditions. The best result have been obtained, in the case of 4-NP, in two compartment reactor type filter-press with nickel cathode (94% of 4-NP removal), and in the case of 2,6-DNP the final removal was of 99% in two compartment reactor with graphite cathode.
REMOVAL OF DYES FROM TEXTILE WASTEWATER BY SORPTION ONTO LIGNO–CELLULOSIC MATERIALS
DANIELA SUTEU(1*), DOINA BILBA(1), CARMEN ZAHARIA(1), ALINA POPESCU(2)
Wastewater from textile industry contains various contaminants, among them dyes are considered to be highly toxic to the aquatic biota. The aim of this paper was to investigate in batch experiments the decolorization of synthetic aqueous solutions containing some cationic and anionic dyes by sorption on lingo-cellulosic solid wastes, such as softwood sawdust. Operating variables studied were: pH, sorbent dose and particle size, dye concentration, temperature and contact time. The sawdust-dye sorption systems were described using Freundlich and Langmuir isotherm models. The obtained results allow to estimate that the sawdust can be useful in implementation of a new cheap technology for textile wastewater treatment.
RECYCLING AND CLOSING OF WATER CIRCUITS IN PAPER MILLS LE RECYCLAGE ET LA FERMETURE DES CIRCUITS DE L'EAU DANS L'INDUSTRIE DU PAPIER
CONSTANTIN STANCIU*, GHEORGHE CANTEMIR
Water plays a basic role in the pulp and paper processes. A modern paper mills generally consumes 10-50 m3 water/tone of paper and removes an equivalent quantity of excess white water polluted with dissolved substances and suspended solids. The paper grade produced is an important factor influencing fresh water consumption and solid losses. To diminish the environmental impact of paper mills, generally speaking, a combination of internal and external actions is necessary: closure of white loop i.e. reduction of fresh water consumption and effluent volume; loss collection and sludge and waste treatment system. The closure of circuits can be carried out by: (i) white water recirculation after removing fibers and fine materials; (ii) restriction of fresh water consumption in white loop. The paper shows in its first part, the problems of closure advantages and disadvantages of closing the circuits of paper machines. The circuit closure in a paper mill drives the following: (1) increase of amount of suspended solids or colloidal substances in white water; (2) increase of amount of organic and inorganic substances dissolved in white water; (3) a rise of temperature in water circuit. Operation difficulties may occur such as: corrosion, deposits and also production conditions are influenced lower retention of fillers, lower dewatering, increase of slime and of foaming odor and quality problems (diminishing of paper mechanical strength by 10% to 20 % or less). The positive effects of circuit closure in paper mill are reduction of fiber and filler losses, reduction of energy costs and investment and operation costs for the treatment plant. The rise of raw and energy costs normally leads to a closure rate of 5 to 10 m3 fresh water/tone of paper. The removal efficiency of soluble materials becomes very important (> 95 %) in terms of restricting the problems related to closure of circuits.
ANALYTICAL CONTROL OF THE NUTRIENTS AND DETERGENTS REMOVAL IN MUNICIPAL WASTEWATER TREATMENT PROCESSES
ELISABETA CHIRILA(1*), CAMELIA LUCIA DRAGHICI(2), CRISTINA ANDREEA TUDOR(1)
The paper presents studies regarding the efficiencies of the removal process for ammonia, nitrites, phosphorus and detergents, in the Constanþa city municipal wastewater treatment plant, during 2007. The pollutants mean concentrations in the effluent, in the studied period, have been according to the imposed limits, but some slightly higher values have been noticed for ammonia during July – October and for total phosphorus during January - March, September and December. The obtained results show that during 2007 high removal efficiencies for ammonium nitrogen (84.79%) and detergents (95.96%) have been obtained but low percentages for phosphorus (47.01%), showing that some operational measures should be taken, in order to improve the removal performances.
RESIDUES OF POLYCYCLIC AROMATIC HYDROCARBONS IN DIFFERENT TYPES OF COFFEE
GABRIELA STANCIU(*), SEMAGHIUL BIRGHILA, SIMONA DOBRINAS
The aim of this work is the development of a simple, fast and quantitative method for polycyclic aromatic hydrocarbons (PAHs) potentially generated by roasting coffee beans. The roasting process is the most important in the coffee industry for the development of the characteristic flavor of the bean mix. The method involves Soxhlet extraction with hexane, clean-up based on silica adsorption chromatography, concentration to dryness and injection of the acetonitrile solution of the residue for HPLC analysis with fluorescence detection. The method allowed confirming or not the presence of the 12 selected PAHs in green coffee and roasted coffee bean samples.
DETERMINATION OF HEAVY METALS CONTENT FROM GRAPES AND MELONS EXTRACTS
VIORICA POPESCU(*), ALINA SOCEANU, SEMAGHIUL BIRGHILA, SIMONA DOBRINAS
Heavy metals are natural components of the Earth’s crust that cannot be degraded or destroyed. As trace elements some of them (e.g. copper, selenium, zinc) are essential to maintain the metabolism of human body, although at higher concentrations they can lead to poisoning. This work is going to present the results obtained from the determinations of grapes and melons extracts. For obtaining the extracts, Soxhlet extraction, maceration and ultrasonic method were used. A Shimadzu atomic absorption spectrometer (Model AA 6200) equipped with air – acetylene flame, was used to determine the Cu, Mn and Zn concentrations. Also, the refraction indices and relative density were measured, using an Abbé refractometer and a picnometer. The obtained results show that the highest Cu and Zn content is in the melons skin, the highest Mn content is in the grapes skin. The refraction indices and the density’s values are very close to that from the Romanian standards. In the last part of this study we are making a comparative analysis with ours previous studies about others fruits extracts heavy metalscontent.
HYDROTHERMAL TREATMENT – A METHOD TO REDUCE THE PHYTATE CONTENT OF THE RYE
OANA CONSTANTIN, IULIANA BANU(*), INA SIMITARU, CORNELIA LUNGU
The purpose of the research was to study the way the hydrothermal treatment influences the phytate content in the rye and to establish the optimal conditions for this treatment in order to obtain rye with reduced phytate content. By applying a hydrothermal treatment under the controlled conditions of temperature and pH, 97.4% of the phytate contained in the rye was hydrolyzed. This is possible because the conditions under which the hydrothermal treatment is performed are the optimal conditions under which the phytate acts upon the phytine. The experimental results indicated as optimal conditions for the phytate degradation the temperature of 55 ºC and the acid solution concentration for the rye soaking of 1.2%.
RHEOLOGY OF GELS CONTAINING PEA PROTEIN ISOLATE ENZYMATICALLY MODIFIED WITH BACTERIAL TRANSGLUTAMINASE
AURELIA IONESCU(1), MARGARETA ZARA(1*), IULIANA APRODU(1), AIDA VASILE(1), GABRIELA GURAU(2)
The present study deals with functional characteristics and rheological behavior of the gels obtained from pea protein isolate enzymatically modified with bacterial transglutaminase (MTGase). During the shearing flow process, the protein gels behaved as non-Newtonian fluids with structural viscosity. The apparent viscosity of all studied gels and their coefficient of viscosity decreased with the increase of the shearing rate in the range 0.1667 – 148.5 s-1. The rheological characteristics of the gels correlated directly with the enzyme level added in the limits 0.1 – 0.25 g/100 g proteins, with the temperature in the range 4 – 40 °C and with the reaction time of the enzyme of 30 – 90 minutes. The aims of the present study were twofold: (i) to study the interaction of MTGase with pea proteins, and (ii) to evaluate the effect of this interaction on functional and rheological characteristics of protein gels in correlation with the level of the added enzyme, with the time and the temperature of reaction.
EFFECT OF CALCIUM CHLORIDE TREATMENT ON THE TENDERIZATION OF ADULT BEEF
DANIELA ISTRATI(*), AURELIA IONESCU
The treatment with calcium chloride is a chemical method to tenderized adult beef that reduce beef hardness and improve rate of ageing resulting more acceptable meat products for consumers [1, 2]. In this study were evaluated the effect of beef cuts injection with 0.4 M sodium chloride (10% w/w), 0.2 M calcium chloride (10% w/w) and 0.4 M calcium chloride (10% w/w), on adult beef at 4 hours post-mortem. The effects generated by samples injection with sodium chloride and calcium chloride was distinguish after 0, 1, 2, 3, 7 days of stored at 4 0C through rigidity index, pH, water holding capacity and cooking losses determination. Between 0 and 24 hours of storage at 4 0C, pH values increased meaningful at all analyzed samples, the smaller values of pH being identified at the control and at the samples injected with CaCl2. After 24 hours of storage at 4 oC, pH values suffer a significant increase but differing in accordance with the nature of samples, after 48 and 72 hours the highest values were identified for the samples injected with 0.4 M CaCl2. The beef cuts injected with sodium chloride and calcium chloride presented increased values of rigidity index as compared to the control resulted an improvement of adult beef tenderness.
INFLUENCE OF THERMAL TREATMENT AND IONIC FORCE ON THE PROPERTIES OF FOAMS CONTAINING SERUM PROTEINS
I. NICORESCU1(*), C. LOISEL(1), C. VIAL(2), A. RIAUBLANC(3), G. DJELVEH(2), G. CUVELIER(4), J. LEGRAND(5)
The aim of our study was to investigate the effect of dynamic thermal treatment on the denaturation and foaming properties of whey proteins, such as overrun, foam stability and texture. Three WPI solutions at 2% w/v (without or with addition of 50 mM and 100 mM NaCl) were heat-treated using a tubular heat-exchanger Actijoule at 100 °C. The native and denatured WPI samples were characterized by chromatography (SEC), dynamic light scattering (DLS) combined with microscopy (FPIA-3000) and micro-differential scanning calorimeter (-DSC). Then, these protein solutions were whipped to produce foams using a Kitchen Aid mixer and foam stability, viscoelastic properties and bubble sizes were measured. Experimental results demonstrated that heat treatment with or without the presence of salt do not lead at an improved overrun. On the other hand, presence of NaCl and heat treatment strongly enhanced firmness and improved foam stability (except for the foam produced from a solution at 50 mM salt). Experimental data have also shown that increasing the proportion of soluble aggregates from 8% (case of the heat treatment without salt) to 70% (case of the heat treatment in presence of 50 mM NaCl) led to a strong improvement in the firmness but also to a more rapid destabilization of foams. It can be asserted that the stability against drainage depends for a great part on controlling the optimal amount of dynamically heat-induced aggregates. A compromise for a better firmness and stability of aggregate-stabilized foams was found for an amount of 17% aggregates in the soluble fraction.
FOAMING OF MODEL MEDIUMS IN LAMINAR FLOW: COMPARISON BETWEEN A ROTOR-STATOR UNIT AND AN AGITATED COLUMN WITH A NARROW ANNULAR GAP
ISSA NARCHI*, CHRISTOPHE VIAL, GHOLAMREZA DJELVEH
Foamed food products, such as chocolate mousse, ice cream and spread cheese are more and more popular because of their sensorial properties. Their behavior under flow, their stability over time and the perception of their properties by the consumers depend strongly on the gas fraction, the average bubble diameter and the bubble size distribution within the matrix. In this work, the objective is to compare the performances of two different continuous foaming devices. The first one is a rotor-stator unit equipped with pins, whereas the second consists of a narrow annular gap unit simulating a scraped surface heat exchanger. Both devices allow to vary the rotation speed between 200 rpm and 1600 rpm and the gas to liquid flow rate ratio (G/L) between 10/30 and 30/30 (mL.min 1)/(mL.min-1). This allows obtaining overrun values in the final product that vary between 33% and 100%. Moreover, the two devices are connected to an on-line image analysis system, which makes it possible to determine the mean bubble diameter (d32) as well as the size distribution within the foamed product. The model matrix is a Newtonian glucose syrup (1 Pa.s) containing 2% (w/w) whey protein (WPI). The influence of the foaming device, the operating conditions and the formulation viscosity were analyzed using the Weber number. Concerning the gas incorporation, the experimental results showed that both devices allowed a total incorporation of the gas phase with an overrun of 100%. However, when G/L = 30/30, the column made it possible to obtain total gas incorporation only for 800 rpm. In the rotor-stator, total incorporation was difficult only at high rotation speed for G/L = 30/30. For bubble size, results showed that d32 was smaller in the column than in the rotor-stator for G/L = 10/30, but that this difference vanished for higher G/L ratio. In both devices, the minimum diameter obtained was slightly lower than 20 µm. Lastly, this work highlighted that the dimensionless Weber number remained constant around 0.3 for the both devices, regardless of operating conditions. The results also showed that the energy transmitted to the fluid was significantly higher in the column than in the rotor-stator. Moreover, total energy dissipation, including mechanical friction, was almost identical in the two devices when G was low and for low rotation speeds. Beyond 1200 rpm, energy consumption was higher in the column and this was accentuated for high G/L ratio. In conclusion, the choice of a foaming unit and the operating conditions depends on the desired properties in terms of overrun, stability and bubble size. The energy criterion, often ignored, can also be discriminating.
IMPRINTED POLYMER PEARLS FOR MOLECULAR RECOGNITION OF DIOSGENIN
ANDREI SARBU(1*), STEFAN-OVIDIU DIMA(1), TANASE DOBRE(2), GINA FLOREA(1), ELENA BACALUM(1), ANITA L. RADU(1), MARIANA BEDA(1), NECULAI ANTOHE(3)
The target of this study was the elaboration of a procedure for diosgenin molecularly imprinted polymers obtaining. The phase inversion method was used and it was aimed to prepare polymer pearls. In order to achieve the molecularly imprinted structures, copolymers of acrylonitrile with acrylic acid were synthesized by radical copolymerization in emulsion without emulsifier. The reaction was initiated by the redox system potassium persulfate – sodium metabisulfite. The research studies allowed the assigning of the best parameters of the casting solution preparation, for the phase inversion and for the extraction. The rheological studies performed in dimethylformamide consolidated the choice upon the conditions for polymers solutions obtaining. The rheological studies revealed changes of the polymer-polymer and polymer-solvent interactions and this could favor the molecular imprinting. These interactions depend on composition and concentration of the copolymer in solution, on concentration of diosgenine and on temperature. By the variation of the phase inversion and extraction conditions it was possible to obtain pearls molecularly imprinted with diosgenin.
PREPARATION AND CHARACTERIZATION OF FUNCTIONAL COPOLYURETHANE WITH MALEIMIDE GROUPS
VIORICA GAINA(*), CONSTANTIN GAINA
Maleimide functionalized copolyurethanes were prepared by the reaction of a binary mixture of dibenzyldiisocyanate and 1-(3,5-diisocyanatophenyl)-1H-pyrrole-2,5-dione with a macrodiol (polyethylene-adipate glycol) using diethylene glycol and trimethylolpropane as chain extender and crosslinkers in toluene-dichloromethane solution. Structures of polymers were confirmed by IR and the properties were also studied by thermal and mechanical analysis, and physical methods (contact angle).
ON USING OF NANO-SIZED ROD-LIKE MAGNETITE PARTICLES FOR DETERMINATION OF BIOLOGICAL BINDING REACTIONS
GABRIELA APREOTESEI (1), RODICA BADESCU(1), OVIDIU ROTARIU(2), LAURA ELENA UDREA(2), VASILE BADESCU(2*)
Rod-like nano-sized magnetite particles have been prepared by direct precipitation from aqueous solutions in the presence of an external magnetic field. Using these particles we prepared ferrofluids which become birefringent when a magnetic field is applied perpendicular to the optical axis of light impinging the fluid. After switching off the magnetizing field, the birefringence relaxes. We observed that for ferrofluids containing rod-like magnetite nanoparticles the dominant relaxation mechanism is the Brownian motion. Since the constant of the Brownian relaxation time depends on the hydrodynamic size of the particles it can be determined by transient magnetic birefringence measurements. Considering the fact that biological binding reactions are always connected to changes in the particle size of the reaction components, our work focuses on the monitoring of binding reactions. For the determination of the binding reaction between an antibody and its antigen the magnetic nanoparticles were conjugated with streptavidin. The biotinylated antibody against human immunoglobulin M (hIgM) was attached to the nanoparticles via the binding between biotin and streptavidin. The presented experiments confirm that the determination of the relaxation of the transient field-induced birefringence of rod-like magnetic nanoparticles can be used for the investigation of binding reactions of antibodies to their antigens.
SYNTHESIS AND CHARACTERIZATION OF SOME ARYLENIMINE POLYMERS CONTAINING N-HEXYL-3,6-CARBAZOLYLDIYL UNITS
IULIA MIHAI(1*), MARIA IVANOIU(1), MIRCEA GRIGORAS(2)
Two monomers with preformed azomethine structures were obtained by condensation reactions of 1,4-phenylenediamine with 3-formyl-N-hexyl carbazole or 3-formyl-N-hexyl-6-bromo carbazole. The corresponding polymers were synthesized by electropolymerization under galvanostatic conditions (I = ct.). The new structures were characterized by Fourier transform-infrared, 1H NMR and UV-VIS methods.
APPLICATIONS OF THIN LAYER CHROMATOGRAPHY (TLC) TO THE SEPARATION AND QUANTIFICATION OF THE VITAMINS D
ANA M. HOSSU(1*), CRISTIANA RADULESCU(1), MIHAELA ILIE(2), IONICA IONITA(1), ELENA I. MOATER(1)
At first era of the fortification, too important quantities of vitamin D were introduced in the foods and the medicinal preparations. In addition, overdoses could be explained by the simple one does that these preparations were free to reach and that certain mothers considered them as of the "tonic" and about it abused. These days, it proves himself that a big one leaves responsibility fall to the manufacturers that masteries little the method of addition and check very poorly the vitamins content D of the marketed forms. The formations of many isomers and degradation products, as well as the presence of various sources of inherent interferences to the sample type containing vitamins D, complicating extremely the development of methods for dosage of these vitamins. The thin layer chromatography (TLC) is the oldest chromatographic technique and the separation methods of the vitamins D by this method were comparatively numerous.