Nitrobenzene Solution Research Articles

Principle of isomorphism and complete scaling for binary-fluid criticality

The extension of the principle of critical-point universality to binary fluid mixtures, known as isomorphism of critical phenomena, has been reformulated in terms of complete scaling, a concept that properly matches asymmetric fluid-phase behavior with the symmetric Ising model. The controversial issue of the proper definition of the order parameter in binary fluid mixtures is clarified. We show that asymmetry of liquid-liquid coexistence in terms of mole fractions originates from two different sources: one is associated with a correlation between concentration and entropy fluctuations, whereas the other source is the correlation between concentration and density fluctuations. By analyzing the coexistence curves of liquid solutions of nitrobenzene in a series of hydrocarbons (from n -pentane to n -hexadecane), we have separated these two sources of asymmetry and found that the leading nonanalytical contribution to the asymmetry correlates linearly with the solute-solvent molecular-volume ratio. Other thermodynamic consequences of complete scaling for binary mixtures, such as an analog of the Yang-Yang anomaly in the behavior of the heat capacity and a curvature correction to the interfacial tension, are also discussed.

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

Solvent-extraction studies provide confirming evidence that meso-octamethylcalix[4]pyrrole acts as an ion-pair receptor for cesium chloride and cesium bromide in nitrobenzene solution. The stoichiometry of the interaction under extraction conditions from water to nitrobenzene was determined from plots of the cesium distribution ratios vs cesium salt and receptor concentration, indicating the formation of an ion-paired 1:1:1 cesium:calix[4]pyrrole:halide complex. The extraction results were modeled to evaluate the equilibria inherent to the solvent-extraction system, with either chloride or bromide. The binding energy between the halide anion and the calix[4]pyrrole was found to be about 7 kJ/mol larger for cesium chloride than for the cesium bromide. The ion-pairing free energies between the calix[4]pyrrole-halide complex and the cesium cation are nearly the same within experimental uncertainty for either halide, consistent with a structural model in which the Cs+ cation resides in the calix bowl. These results are unexpected since nitrobenzene is a polar solvent that generally leads to dissociated complexes in the organic phase when used as a diluent in extraction studies of univalent ions. Control studies involving nitrate revealed no evidence of ion pairing for CsNO3 under conditions identical to those where it is observed for CsCl and CsBr.

Impact of Fenton and ozone on oxidation of wastewater containing nitroaromatic compounds

Fenton and ozone treatment was investigated at laboratory scale for the degradation of aqueous solutions of nitrobenzene (NB). Effects of reactants concentration (03, H2O2, and Fe(II)), temperature, and pH on NB degradation were monitored. Reaction kinetic of these processes was also assessed. A rapid reaction took place for Fenton process at higher initial concentration of H2O2, higher temperatures, and more acidic conditions (pH 3). Similarly, ozonation reaction exhibited rapid rates for higher ozone dose, higher temperatures, and more basic conditions (pH 11). Complete NB degradation in 65 min was achieved using Fenton process. The conditions of complete elimination of 100 mgfL of initial NB concentration, were 250 mg/L of H2O2 concentration, pH 3, and 10 mg/L of Fe(II) concentration. Under these conditions, 55% organic carbon elimination was achieved. Total organic carbon mineralization was attained in 240 min reaction time by Fenton process with 900 mg/L of H2O2 concentration, and 30 mg/L of Fe(II) concentration. Fenton reaction showed a pseudo-first order kinetic; the reaction rate constant was ranged from 0.0226 to 0.0658 min(-1). Complete NB degradation was also achieved for an ozone dose of the order of 2.5 g/L. The ozonation was studied at different ozone doses, different initial pH (7-11) and at different temperatures (15-35 degrees C). NB ozonation kinetic was represented by a bi-molecular kinetic model which was reduced to pseudo-first order kinetic. The pseudo-first order reaction rate constant was determined to increase at 20 degrees C from 0.004 to 0.020 min(-1) as the used ozone increased from 0.4 to 1.9 g/L.

Pilot‐Scale Degradation of Organic Contaminants in a Continuous‐flow Reactor by the Helielectro‐Fenton Method

AbstractThe feasibility of pilot‐scale mineralization of organic pollutants in wastewaters using the Electro‐Fenton® process is demonstrated. The treatment was applied in a continuous‐flow reactor, to solutions of nitrobenzene, 2,4‐D and benzoic acid and to actual wastewaters from a fine chemicals company along with a pulp and paper company. The results showed mineralization yields from 60 to 84% by simply applying the Electro‐Fenton® process. When a subsequent exposure to sunlight was carried out (Helielectro‐Fenton method), this mineralization almost went to completion, except for the effluent from the fine chemicals industry.

Extraction of microamounts of calcium into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of dibenzo-21-crown-7 and dibenzo-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, CaL2+, CaL22+ and CaHL23+ (L = DB21C7, DB24C8) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Extraction of microamounts of europium and americium by using hydrogen dicarbollylcobaltate in the presence of dibutyl diethylcarbamoylmethylene phosphonate

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of dibutyl diethylcarbamoylmethylene phosphonate (DBDECMP, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL22+ ML33+ and ML43+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Extraction distributions of microamounts of strontium and barium in the two-phase water-HCl-nitrobenzene-dibenzo-21-crown-7-hydrogen dicarbollylcobaltate system

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of dibenzo-21-crown-7 (DB21C7, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, ML2+, ML22+ and MHL23+ (M2+ = Sr2+, Ba2+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Solvent extraction of microamounts of cesium into nitrobenzene by using potassium and rubidium dicarbollylcobaltates in the presence of benzo-15-crown-5

Extraction of microamounts of cesium by nitrobenzene solutions of potassium dicarbollylcobaltate (K+B−) and rubidium dicarbollylcobaltate (Rb+B−) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The equilibrium data have been explained assuming that the complexes ML+ and ML2+ (M+ = K+, Rb+, Cs+) are present in the organic phase. The stability constants of the species ML+ and ML2+ (M+ = K+, Rb+) in nitrobenzene saturated with water have been determined.

Solvent extraction of microamounts of strontium and barium from water into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of benzo-18-crown-6

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−1) in the presence of benzo-18-crown-6 (B18C6, L) has been investigated. The equilibrium data been explained assuming that the complexes HL+, ML2+, ML 2 2+ and MHL 2 3+ (M2+ = Sr2+, Ba2+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Extraction Distribution of Microamounts of Strontium in the Two-Phase Water–RbCl–15-Crown–5-Nitrobenzene–Rubidium Dicarbollylcobaltate System

Extraction of microamounts of strontium by a nitrobenzene solution of rubidium dicarbollylcobaltate (Rb+B-) in the presence of 15-crown-5 (15C5,L) has been investigated. The equilibrium data have been explained assuming that the complexes RbL+, RbL2 + and SrL2 2+ are extracted into the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined.

Photochemistry in the mixed aqueous solution of nitrobenzene and nitrous acid as initiated by the 355nm UV light

The 355 nm photon-initiated microscopic reaction mechanisms of the mixed aqueous solution of nitrobenzene and nitrous acid in the presence or absence of O(2) were studied by the laser flash photolysis technique. The main transient absorption peaks in the recorded spectra were assigned and the growth/decay trends of several transient species were investigated. It was found that the OH radical formed from the photolysis of nitrous acid triggered most of the subsequent radical reactions. The rate constant of the reaction between OH radical and nitrobenzene was measured to be (3.4 +/- 0.1) x 10(9) l mol(-1) s(-1). The product from this reaction, namely C(6)H(5)NO(2)-OH adduct, was found to react with O(2) to yield C(6)H(5)NO(2)-OHO(2) adduct with a rate constant of (1.6 +/- 0.2) x 10(9) l mol(-1) s(-1). Final steady-state products were identified by GC/MS analysis and were in accordance with the transient spectroscopic results. The possible reaction pathways were proposed.

Molecular dynamics study of dicarbollide anions in nitrobenzene solution and at its aqueous interface. Synergistic effect in the Eu(iii) assisted extraction

We report a molecular dynamics study of chlorinated cobalt bis(dicarbollide) anions [(B(9)C(2)H(8)Cl(3))(2)Co](-)"CCD(-)" in nitrobenzene and at the nitrobenzene-water interface, with the main aim to understand the solution state of these hydrophobic species and why they act as strong synergists in assisted liquid-liquid extraction of metallic cations. Neat nitrobenzene is found to well solubilize CCD(-), Cs(+) salts in the form of diluted pairs or oligomers, without displaying aggregation. In biphasic nitrobenzene-water systems, CCD(-) anions mainly partition to the organic phase, thus attracting Cs(+) or even more hydrophilic counterions like Eu(3+) into that phase. The remaining CCD(-) anions adsorb at the interface, but are less surface active than at the chloroform interface. Finally, we compare the interfacial behavior of the Eu(BTP)(3)(3+) complex in the absence and in the presence of CCD(-) anions and extractant molecules. It is found that in the absence of CCDs, the complex is trapped at the interface, while when the CCDs are concentrated enough, the complex is extracted to the nitrobenzene phase. These results are compared to those obtained with chloroform or octanol as organic phase and discussed in the context of synergistic effect of CCDs in liquid-liquid extraction, pointing to the importance of dual solvation properties of nitrobenzene or octanol to solubilize the CCD(-) salts as well as the extracted complex.

Thermal Modulation Voltammetry with Laser Heating at an Aqueous|Nitrobenzene Solution Microinterface: Determination of the Standard Entropy Changes of Transfer for Tetraalkylammonium Ions

Thermal modulation voltammetry (TMV) with laser heating was successfully performed at an aqueous|nitrobenzene (NB) solution microinterface, by taking advantage of the fact that laser light with a wavelength of 325.0 nm is optically transparent to the aqueous solution but opaque to the NB solution. When the laser beam impinges upon the interface from the aqueous solution side, a temperature is raised around the interface through the thermal diffusion subsequent to the light-to-heat conversion following the optical absorption by the NB solution near the interface. Based on such a principle, we achieved a fluctuating temperature perturbation around the interface for TMV by periodically irradiating the interface with the laser beam. On the other hand, the fluctuating temperature perturbation has influence on currents for transfer of an ion across the interface to produce fluctuating currents synchronized with the perturbation through temperature coefficients of several variables concerning the transfer, such as the standard transfer potential and the diffusion coefficient of the ion. Consequently, TMV has the possibility of providing information about the standard entropy change of transfer corresponding to a temperature coefficient of the standard transfer potential and a temperature coefficient of the diffusion coefficient. In this work, the aqueous|NB solution interface of 30 microm in diameter was irradiated with the laser beam at 10 Hz, and the currents synchronized with the periodical irradiation were recorded as a function of the potential difference across the interface in order to construct a TM voltammogram. TM voltammograms were measured for transfer of tetramethylammonium, tetraethylammonium, tetrapropylammonium, and tetra-n-butylammonium ions from the aqueous solution to the NB solution, and the standard entropy change of transfer was determined for each ion, according to an analytical procedure based on a mathematical expression of the TM voltammogram. Comparison of the values obtained in this work with the literature values has proved that TMV with laser heating is available for the determination of the standard entropy change of transfer for an ion.

Characterization and Pumping: Redox Magnetohydrodynamics in a Microfluidic Channel

By adding redox species, both aqueous and nonaqueous solutions can be pumped along the length of a microfluidic channel when low voltages (to produce current) are applied across the channel’s breadth in the presence of a magnetic field applied across its height. Control of flow rate is possible by varying the magnitudes of the voltage and magnetic field and by changing the redox concentration. Direction is determined by the voltage polarity and magnetic field orientation. We have demonstrated a dc redox magnetohydrodynamic (MHD) pump in microchannels ( wide deep long) that were constructed from low-temperature cofired ceramics with screen-printed gold electrodes on opposing sidewalls. Redox MHD involves the generation of current between the electrodes in a solution through the oxidation/reduction of redox species in the presence of a magnetic field. When the current and magnetic fields are perpendicular, a Lorentz force results, causing fluid flow along the length of the channel. The pumping performance was investigated as a function of type and concentration of redox species, magnetic flux density, applied voltage, and time scale. Studies show bidirectional capability by changing the direction of the current. Flow velocities of up to were observed in a solution of nitrobenzene (NB) and tetrabutylammonium hexafluorophosphate in acetonitrile using a permanent magnet, at an applied voltage of vs (saturated ) (approximately a potential difference of between wall electrodes in the microchannel) and the corresponding current enhancements (caused by the increased convection) were as large as 145%. Flow rates for NB and NB in in acetonitrile were measured at three different applied voltages near the redox potential of NB. Comparisons were also made to theory. A mixture of oxidized and reduced forms of the same redox couple, instead of a single species like NB, can avoid electrode dissolution at the oxidizing electrode (or bubble generation at either electrode). One example of this approach involves a solution of and in and another involves a solution of and in , where potential differences between wall electrodes in the microchannel can be less than . Findings from these studies should be useful in development of sealed microanalytical devices using redox MHD pumps with possible lab-on-a-chip applications.

Synthesis of 1,8-cineole and 1,4-cineole by isomerization of α-terpineol catalyzed by heteropoly acid

The isomerization of α-terpineol ( 1) catalyzed by heteropoly acid H 3PW 12O 40 (PW) in homogeneous and heterogeneous systems yields 1,8-cineole ( 2) and 1,4-cineole ( 3), both useful for flavoring and pharmaceutical applications. In the homogeneous system, 2 and 3 were obtained with 25% and 23–27% selectivity, respectively, at 50–90% α-terpineol conversion (in a nitrobenzene solution, 40 °C). In the heterogeneous system, 35% of 2 and 25% of 3 were obtained at 70–100% conversion in a cyclohexane solution at 60 °C using silica-supported PW as a solid acid catalyst, and the catalyst could be recycled. PW showed a higher catalytic activity and selectivity than conventional acid catalysts such as H 2SO 4 and Amberlyst-15.

The effect of electrolytic oxidation on the electrochemical properties of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWNTs) were electrochemically oxidized by a constant-potential electrolysis method and then investigated in detail using scanning electron microscope, transmission electron microscope, FT-IR, electrical impedance spectroscopy, and cyclic voltammetry. The FT-IR spectra showed that the amount of hydroxyl generated on the surface of MWNTs increased with increasing the electrochemical oxidation time of MWNTs. The CV results, being conducted in nitrobenzene solution, showed that the nitrobenzene reduction current increased with the increase in oxidation time of the MWNTs within the first 60 min of electrolysis. An electrical equivalent circuit model for electrical impedance spectroscopy was further established to analyze the surface capacitance and resistance of the MWNTs, and the model results showed that the capacitance of the oxidized MWNTs increased greatly while the charge transfer resistance decreased, suggesting electrochemical oxidized MWNTs modified pyrolytic carbon electrode being an effective electrochemical sensor for nitrobenzene determination.

Effect of a solid substrate on orientational ordering and the process of associate formation in thin interlayers of solutions of some organic compounds

We have studied the vibronic absorption spectra of thin submicron interlayers of anisole and nitrobenzene solutions as a function of the concentration and thickness of the interlayer. We have observed isosbestic points in a series of spectra obtained for different concentrations and thicknesses. This in turn is due to the existence in the system of two types of absorbing centers, which we connect with monomers and molecular associates (dimers). We discuss the relative contribution of different types of interactions leading to dimer formation.

Extraction of microamounts of calcium from water into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of Slovafol 909

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of Slovafol 909 (L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL, CaL2+ and CaL are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Separation of microamounts of yttrium from strontium by using sodium dicarbollylcobaltate, Slovafol 909 and ethylenediamine - N, N, N', N'-tetraacetic acid in the water - nitrobenzene extraction system

A rapid extraction separation of trace amounts of yttrium from stron tium by a nitrobenzene solution of sodium dicarbollylcobaltate (NaDCC) in the presence of p -nonylphenylnonaethylene glycol (Slovafol 909) and tetrasodium salt of ethylenediamine – N,N,N’,N’ – tetraacetic acid (Na 4L) in the aqueous phase was developed. The separation factor α(Sr/Y) was substantially higher than 10 5 . This water -nitrobenzene extraction system can be applied for the efficient separation of carrier -free 90 Y from 90 Y/ 90 Sr generator.

Ion distributions at the nitrobenzene–water interface electrified by a common ion

Synchrotron X-ray reflectivity is used to study ion distributions at the liquid-liquid interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate (TBATPB) and a water solution of tetrabutylammonium bromide (TBABr). The concentration of TBABr is varied to alter the ion distribution. Our X-ray measurements are inconsistent with several commonly used theories of ion distributions, including Gouy-Chapman, modified Verwey-Niessen, and the MPB5 version of the Poisson-Boltzmann equation. These structural measurements are described well by ion distributions predicted by a version of the Poisson-Boltzmann equation that explicitly includes a free energy profile for ion transfer across the interface when this profile is described by a simple analytic form or by a potential of mean force from molecular dynamics simulations. These X-ray measurements from the liquid-liquid interface provide evidence for the importance of interfacial liquid structure in determining interfacial ion distributions.