Benzoic Acid In Aqueous Solutions Research Articles

Complexation of uranyl with benzoic acid in aqueous solution at variable temperatures: potentiometry, spectrophotometry and DFT calculations.

Investigation of the fundamental coordination chemistry between U(VI) and simple organic ligands is important to understand the chemical behavior of U(VI) in the natural environment and separation processes. In this work, the complexation of U(VI) with a common carboxylic acid, benzoic acid, has been systematically investigated through potentiometry, spectrometry and DFT calculations. Three successive complexes (UO2L+, UO2L2 and UO2L3-, L = benzoate ion) between U(VI) and benzoic acid are successfully identified in aqueous solution and their corresponding thermodynamic parameters (stability constant, enthalpy and entropy) are determined. Notably, this is the first time that the previously missing 1 : 2 and 1 : 3 (U to L) complexes in aqueous solution and their complexation thermodynamics have been reported, which would aid in more accurate prediction of the chemical behavior of U(VI) in the presence of benzoic acid. Moreover, the structures of the complexes are elucidated using DFT calculations, which show that benzoic acid coordinates to U(VI) in a bidentate form in all the complexes.

Spray deposited Fe2O3 and stratified Fe2O3/ZnO novel photoelectrode for photoelectrocatalytic degradation of benzoic acid under solar light illumination

Fe2O3 and stratified Fe2O3/ZnO thin films are successfully synthesized by chemical spray pyrolysis technique. Synthesized films are used to study the photoelectrochemical (PEC), structural, morphological and optical properties. The maximum PEC response is observed for stratified Fe2O3/ZnO photoelectrode (Isc = 0.850 mA and Voc = 948 mV). All the films are polycrystalline nature with rhombohedral and hexagonal crystal structures for Fe2O3 and ZnO phase respectively is conformed from XRD analysis. Surface morphology of stratified Fe2O3/ZnO film shows the cluster of petal like grains on the surfaces of film. The estimated band gap energy of prepared Fe2O3 and stratified Fe2O3/ZnO thin films are 2.10 and 2.65 eV respectively. Finally large area (100 cm2) deposited Fe2O3 and stratified Fe2O3/ZnO photoelectrodes are used to study the photoelectrocatalytic degradation of benzoic acid (BA) under solar radiation. The higher degradation result is observed in case of stratified Fe2O3/ZnO than Fe2O3 photoelectrode and it is about 74% in 320 min. The mineralization of BA in aqueous solution is study with the help of chemical oxygen demand (COD). The observed results indicate that stratified Fe2O3/ZnO photoelectrode is promising candidate for degradation of BA.

Photoelectrocatalytic degradation of benzoic acid using immobilized tungsten trioxide photocatalyst

The thin films of WO3 were deposited with different solution quantities using chemical spray pyrolysis technique. The WO3 film thickness effect on the photoelectrochemical, structural, morphological and optical properties is studied. Polycrystalline, monoclinic WO3 films possess photoelectrochemical performance having onset potentials around +0.3 V/SCE in 0.01 M HClO4. The maximum photocurrent density (Iph = 635 μA/cm2) is observed for the film deposited with 75 ml solution quantity. The FE-SEM image shows compact structure with petals like morphology. The estimated indirect band gap of WO3 films lies in the range of 2.60–2.65 eV. The photoelectrocatalytic degradation of benzoic acid is studied using WO3 photoelectrode under UV light illumination and 57 ± 3% removal of benzoic acid is achieved. The mineralization of benzoic acid in aqueous solution has been studied by measuring COD values.

A thermo-sensitive supramolecular hydrogel derived from an onium salt with solution–gel–crystal transition properties

A self-assembled supramolecular hydrogel, which not only exhibits thermo-sensitive characteristics but has the property of solution–gel–crystal transition, is obtained by mixing the aqueous solutions of benzoic acid and melamine.

Inkjet-printed interdigitated cells for photoelectrochemical oxidation of diluted aqueous pollutants

Planar, interdigitated photoelectrochemical cells were made by inkjet printing. The electrode fingers had widths ranging from 200 to 1500 µm and were revealed by printing a positive protective polymer mask on fluorine-doped tin oxide-coated glass slides and subsequent etching. One finger family was overprinted by an ink-jettable sol–gel composition based on titanium propoxide which was then converted into TiO2 by annealing in air. An incident photon to current conversion efficiency of 0.19 was obtained at 360 nm for 200-nm-thick films. The influence of electrode geometry and titania thickness on the electrochemical properties of resulting cells is discussed in detail. Due to the interdigitated layout, photoelectrochemical response was not suffering from iR drop down to low electrolyte ionic strengths. The printed cells were used in photoelectrocatalytic degradation experiments of aqueous solutions of benzoic acid by broadband ultraviolet irradiation (UVA) and electric bias of 1 V and delivered considerable acceleration of the degradation process compared to the plain photocatalytic mode.

Enhancement photo-catalytic degradation of benzoic acid using the heterosystem NiCo2O4/ZnO

The present work focused on the degradation of benzoic acid in aqueous solutions using the heterosystem NiCo2O4/ZnO as a semi-conductor. The material NiCo2O4 is prepared by a nitrate method and characterized by several techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), reflectance diffuse (RD), electrical conductivity and the photo-electrochemical (PEC) characterizations. Under visible light, the benzoic acid degradation using a heterosystem NiCo2O4/ZnO is investigated. Several parameters are examined as the pH, the heterosystem ratio and the initial benzoic acid concentration. The results reveal that, as pH value increased from 2 to 6, the photo-degradation raised and the removal efficiencies attend the value 71%. The optimum results exhibited an enhancement photo-activity at a neutral pH and with a heterosystem ratio 50/50. The high efficiency is due to the present of unique structure constructed which increases the amount of electro-active sites and facilitates the electrolyte penetration via the electron transfer. Thus, the kinetic analysis showed that the photo-degradation rates can be approximated to be pseudo-first order, according to the Langmuir–Hinshelwood kinetics model.

Study on degradation kinetics of 2-(2-hydroxypropanamido) benzoic acid in aqueous solutions and identification of its major degradation product by UHPLC/TOF–MS/MS

A RP-HPLC method was developed and validated for the degradation kinetic study of 2-(2-hydroxypropanamido) benzoic acid (HPABA), a promising anti-inflammatory drug, which would provide a basis for further studies on HPABA. The effects of pH, temperature, buffer concentration and ionic strength on the degradation kinetics of HPABA were discussed. Experimental parameters such as degradation rate constants (k), activation energy (Ea), acid and alkali catalytic constants (kac, kal), shelf life (t1/2) and temperature coefficient (Q10) were calculated. The results indicated that degradation kinetics of HPABA followed zero-order reaction kinetics; degradation rate constants (k) of HPABA at different pH values demonstrated that HPABA was more stable in neutral and near-neutral conditions; the function of temperature on k obeyed the Arrhenius equation (r=0.9933) and HPABA was more stable at lower temperature; with the increase of ionic strength and buffer concentration, the stability of HPABA was decreased. The major unknown degradation product of HPABA was identified by UHPLC/TOF–MS/MS with positive electrospray ionization. Results demonstrated that the hydrolysis product was the primary degradation product of HPABA and it was deduced as anthranilic acid.

Photocatalytic degradation of phenol and benzoic acid using zinc oxide powders prepared by the sol–gel process

Photocatalytic degradation of phenol and benzoic acid in aqueous solution was studied using zinc oxide (ZnO) powder synthesized by sol–gel process. Synthesized catalyst was characterized by X-ray diffraction and transmission electron microscopy. The Brunauer–Emmett–Teller surface area, pHpzc, and the band gap of the catalyst samples were also measured. The influence of various key parameters such as amount of photocatalyst, initial solution pH, and the initial concentration of phenol and benzoic acid was investigated.

Adsorption of Benzoic Acid in Aqueous Solution by Bagasse Fly Ash

This paper reports the studies on the benzoic acid (BA) onto bagasse fly ash (BFA) was studied in aqueous solution in a batch system. Physico-chemical properties including surface area, surface texture of the GAC before and after BA adsorption onto BFA were analysed using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The optimum initial pH for the adsorption of BA was found to be 5.56. The adsorbent dose was 10 g/l for BFA and the equilibrium time 8 h of reaction. Pseudo first and second order models were used to find the adsorption kinetics. It was found that intraparticle diffusion played important role in the adsorption mechanisms of BA and the adsorption kinetics followed pseudo-second order kinetic model rather than the pseudo first order kinetic model. Isotherm data were generated for BA solution having initial concentrations of BA in the range of 10–200 mg/l for the BFA dosage of 10 g/l at temperatures of 288, 303, and 318 K. The adsorption of BA onto BFA was favorably influenced by an increase in temperature. Equilibrium data were well represented by the Redlich–Peterson isotherm model. Values of the change in entropy (ΔS 0), heat of adsorption (ΔH 0) for adsorption of BA on BFA was found to be 120.10 and 19.61 kJ/mol respectively. The adsorption of BA onto BFA was an endothermic reaction. Desorption of BA from BFA was studied by various solvents method. Acetic acid was found to be a better eluant for desorption of BA with a maximum desorption efficiency of 55.2 %. Owing to its heating value, spent BFA can be used as a co-fuel for the production of heat in boiler furnaces.

Complex formation of native and hydroxypropylated cyclodextrins with benzoic acid in aqueous solution: Volumetric and 1H NMR study

Novel data on complexation of benzoic acid by parent and hydroxypropylated cyclodextrins were obtained by densimetry and 1H NMR. Formation of 1:1 inclusion complexes was detected in most cases with the exception of hydroxypropyl-γ-cyclodextrin, which is able to form 1:2 complexes. The data demonstrated penetration of carboxylic group of benzoic acid inside macrocyclic cavity, its insertion into β-cyclodextrin cavity being deeper. Binding constants and volumes of transfer were calculated and analyzed in terms of influence of cyclodextrin structure on binding mode and driving forces of interaction as well as on the complex stability.

Wet oxidation of benzoic acid catalyzed by cupric ions: Key parameters affecting induction period and conversion

The catalytic wet oxidation (CWO) of aqueous solutions of benzoic acid (BA) has been thoroughly investigated using various copper- and iron-containing catalysts with emphasis on cupric nitrate. The influence of BA concentration ranging from 50 to 150mg/L, catalyst loading varying between 50 and 150mg/L (i.e. 14 and 40mgCu/L), reaction temperature in the range 150–180°C and oxygen partial pressure in the range 10–30bar on the induction period of the reaction and BA conversion has been extensively studied. A factorial experimental design methodology has been implemented to assess the significance of the aforementioned parameters and a mathematical model has been proposed. The induction period observed during the CWO of BA is strongly affected by the reaction temperature and to a lesser extent by the initial BA concentration, the oxygen partial pressure, as well as by the second order interaction between initial BA concentration and oxygen partial pressure. Differences in chemical structure account for different reactivities: electron-donating substituents (i.e. methoxy- or hydroxyl-group) seem to increase the reactivity of benzoic acid, whereas the presence of electron-withdrawing substituents, such as nitro-group, decreases the reactivity of the molecule. Hydroxylation of the aromatic ring is an important pathway during the CWO of BA.

Poly[μ-aqua-di-μ-benzoato-lead(II)

The reaction of lead(II) nitrate and benzoic acid in aqueous solution yields the title polymer, [Pb(C7H5O2)2(H2O)]n. The asymmetric unit contains one PbII ion, two benzoate ligands and one water mol­ecule. The Pb—O bond distances are in the range 2.494 (4)–2.735 (4) Å. The Pb⋯Pb distance is 4.0683 (4) Å, indicating an insignificant metal–metal inter­action. The PbII atom has a distorted penta­gonal-bipyramidal geometry chelated by two carboxyl­ate O atoms. The Pb atoms are bridged through a coordinating water mol­ecule and two carboxyl­ate O atoms from another two benzoate ligands, giving an infinite three-dimensional supra­molecular structure. O—H⋯O hydrogen-bonding inter­actions involved the coordinating water and carboxyl­ate O atoms enhance the stability of the supra­molecular arrangement.

Pilot scale mineralization of organic acids by electro-Fenton ® process plus sunlight exposure

The viability of the electro-Fenton ® degradation of aqueous solutions of benzoic acid, 2,4-dichlorophenoxyacetic acid and oxalic acid has been studied at 20 A using a pilot flow reactor containing an anode and an oxygen diffusion cathode, both of 100 cm 2 section. Pollutants were preferentially oxidized by hydroxyl radicals formed in solution from reaction of Fe 2+ with electrogenerated H 2O 2, allowing mineralization of benzoic acid and 2,4- D. For oxalic acid no electrochemical mineralization was observed. After electrolysis, samples of the different effluents were exposed to sunlight (Helielectro-Fenton process) and almost complete mineralization was reached after ca. 30–50 min without additional cost. Effects of parameters such as electrolysis time, pH and solar irradiation time on the process efficiencies were studied.

Time-dependent conversion of benzyl alcohol to benzaldehyde and benzoic acid in aqueous solutions

The oxidative reaction: benzyl alcohol–benzaldehyde–benzoic acid was investigated in time in aqueous solutions of benzyl alcohol widely used as a preservative in medicine and cosmetology. The solutions of benzyl alcohol were stored at concentrations from 0.005 to 2.09 mg/ml for a long time under different conditions. The presence of benzaldehyde and benzoic acid in these solutions was controlled by liquid chromatography on silica sorbent in water. The content of benzoic acid and potentially toxic benzaldehyde in solutions depending on the initial concentration of benzyl alcohol, on time, and on storage conditions was evaluated quantitatively.

Oxidation of Benzoic Acid by Electrochemically Generated Ce(IV)

This paper presents a study of the oxidation of benzoic acid in aqueous solutions by Ce(IV), which functions as an electrogenerated mediator. In this reaction, benzoic acid is oxidized to CO2, and the reaction displayed pseudo-first-order kinetics for the conditions 0.15-0.45 mM Ce(SO4)2, 0.5-3.0 mM benzoic acid, and 0.2 M H2SO4 at 25 degrees C. The k1 values were in the range 0.40 x 10(-4)-0.59 x 10(-4) s(-1) and increased with temperature within the range studied, 25-45 degrees C. The activation parameters for the reaction, deltaH++, deltaG++, and deltaS++, were determined to be 10.5 kcal/mol, 23.3 kcal/mol, and -43 cal/(mol K), respectively. The electrolysis of Ce(III) in a stirred solution at 25 degrees C and with 1.5 V constant potential generated a 96% Ce(IV)-4% Ce(III) distribution in 140 min. The k for the generation of Ce(IV) was 0.0003 s(-1). Electrolysis under similar conditions but with a large excess of benzoic acid in solution produced a steady-state conversion of 87% Ce (IV) and the corresponding k was 0.00027 s(-1). This reduction in k is consistent with the relative magnitudes of the oxidation reactions for Ce(III) and benzoic acid. Correspondingly, the electrolysis of benzoic acid (0.594 mM) in a 0.2 M H2SO4 solution containing 0.25 mM Ce2(SO4)3 was accomplished by applying 1.5 V to the stirred solution at 25 degrees C. The benzoic acid concentration was reduced to 0.026 mM, or by 96%, in 456 h. In this experiment the potential was applied for 3 h and then turned off for 48 h, and the sequence was repeated 8 times.

Raman spectroscopic study of the conformational order of octadecylsilane stationary phases: effects of electrolyte and pH

This study investigates effects of the electrolyte, of acidic and basic compounds, and of pH on the rotational and conformational order of octadecylsilane stationary phases with surface coverages of 3.09 and 6.45 micromol/m(2). Both phases exhibit an increase in alkyl chain rotational and conformational order in 5-200 mM aqueous electrolyte solutions relative to water. These stationary phases are effectively "salted-out" of aqueous electrolyte solutions, thereby causing alkyl chain intermolecular interactions to increase with a concomitant increase in alkyl chain order. Although the presence of acidic and basic compounds generally has no effect on the conformational order of either stationary phase as a function of pH, the higher coverage stationary phase does exhibit pH-dependent changes in aqueous solutions of benzoic acid. At pH values below the pK(a) of benzoic acid, the conformational order of this stationary phase is unchanged relative to that observed in the same pH solution in the absence of benzoic acid. In light of independent evidence that such monosubstituted aromatics interact with the octadecylsilane stationary phase under these conditions, the absence of a measurable effect on alkyl chain order for these conditions is attributed to benzoic acid self-association at the stationary phase-mobile phase interface. In contrast, at pH values above the pK(a) of benzoic acid, slight disordering of the alkyl chains is observed and is attributed to repulsive interactions between retained benzoate anions.

The mechanism of the sonochemical degradation of benzoic acid in aqueous solutions

The sonolytic degradation of benzoic acid in aqueous solution was investigated at an ultrasonic frequency of 355 kHz. The degradation rate was found to be dependent upon the solution pH and the surface activity of the solute. The degradation rate was favoured at a solution pH lower than the pK a of benzoic acid. At pH < pK a, HPLC, GC and ESMS analysis showed that benzoic acid could be degraded both inside the bubble by pyrolysis and at the bubble/solution interface by the reaction with OH radicals. At higher pH (> pK a) benzoic acid could only react with OH radicals in the bulk solution. During the sonolytic degradation of benzoic acid, mono-hydroxy substituted intermediates were observed as initial products. Further OH radical attack on the mono-hydroxy intermediates led to the formation of di-hydroxy derivatives. Continuous hydroxylation of the intermediates led to ring opening followed by complete mineralization. Mineralization of benzoic acid occurred at a rate of < 40μM/h.

Enhancement of solid dissolution process

The enhancement of the dissolution rate of the sparingly soluble benzoic acid in aqueous solution by solid rotation, ultrasound and chemical reaction was investigated. The analysis indicated the strong influence of the ultrasound energy dissipation rate on the enhancement. The overall enhancements due to the three means were compared. The enhancement due to ultrasound was found to be much greater than mechanical rotation and comparable to that of chemical reaction.

Removal of benzoic acid in aqueous solution by Fe(III) homogeneous photocatalysis

The behaviour of the system Fe(III)/Air/UV–benzoic acid is investigated in the pH range 2.0–5.5 and Fe(III) concentration up to 60 μM . The oxidation process develops through the establishment of an iron cycle in which HO radicals are produced by Fe(OH) 2+ photolysis and the resulting Fe(II) photo-oxidized to Fe(III) by dissolved oxygen. A kinetic model is developed and used to simulate the behaviour of the system.

Partial molar volumes of organic solutes in water. IV. Benzoic and hydroxybenzoic acids at temperatures fromT = 298 K toT = 498 K and pressures up to 30 MPa

Density data for dilute aqueous solutions of benzoic acid and three hydroxybenzoic acids obtained in the temperature range 298.15 K to 498.15 K and at either atmospheric pressure or at pressures close to the saturated vapour pressure of water and at elevated pressures up to 30 MPa are presented along with partial molar volumes calculated from the experimental data. The data were obtained by using both a high-temperature high-pressure flow vibrating-tube densimeter and a commercial vibrating-tube cell DMA 602HT.