Aqueous Acid Medium Research Articles

Understanding of lactobionic acid in aqueous-glycol mixtures at different temperatures: Ultrasonic investigation and spectroscopic study

The proposed investigation focused on the study of liquid mixtures that contain polyethylene glycols (PEGs) such as polyethylene glycol-200 and polyethylene glycol-400, and lactobionic acid aqueous solutions. The study aimed to examine the density and ultrasonic speed of these mixtures at different temperatures (288.15 K, 298.15 K, 308.15 K, and 318.15 K) and concentrations (0.01, 0.02 and 0.03) mol.kg-1 of lactobionic acid in aqueous medium. The experimental data obtained were used to estimate various density and sound-speed characteristics, and to calculate the apparent molar, partial molar, and transfer properties of volume and isentropic compressions, including (Vϕ, Vϕ0, ΔVϕ0 and Kϕ,s,Kϕ,s0, ΔKϕ,s0). The interaction coefficients (VAB, VABB, KAB and KABB) were determined using the values of ΔVϕ0and ΔKϕ,s0. Additionally, the study computed the limiting apparent molar expansibilities, its derivative, and empirical parameters. The findings of the study were evaluated in terms of interactions among the solutes and solvents in the liquid mixtures. Moreover, the spectroscopic study of the binary mixture of lactobionic acid and water at different their concentrations was done to find the different stretching and bonds available in the mixture.

Insight into D-galactose Oxidation: Kinetic and Mechanistic Analysis with Imidazolium Fluorochromate

In a 50% (v/v) aqueous acetic acid medium, a study on the oxidation kinetics of D-galactose by imidazolium fluorochromate (IFC) was conducted. The study revealed unit-order dependence on [D-galactose], [IFC], and [perchloric Acid]. The reaction was catalyzed by perchloric acid, and followed a 1:1 stoichiometric ratio. Adding sodium hyperchlorate (VII) salt did not affect the reaction. Polymerization of acrylonitrile was not observed in the oxidation process. The oxidation rates were retarded on adding Mn2+ ions in the mixture, and rates increased as the reaction medium’s dielectric constant (D) decreased. The observed results follow the Amis and Kirkwood plots {log k1 vs. (1/D) and ((D-1/2D+1))}. Several thermodynamic variables were determined by analyzing the kinetic data across a temperature range. Arabinose and formic acid were formed as the products of the reaction. A mechanistic path involving the formation of an ester followed by hydride ion transfer was proposed.

Synthesis, characterization, and optical studies of lead-free perovskite, Cs3M2Br9 (M = Bi, Sb) nanocrystals

In recent years, there has been a surge in research interest surrounding all inorganic lead perovskite nanocrystals (NCs) owing to their exceptional performance in various optoelectronic devices. Nevertheless, the presence of lead and concerns regarding its toxicity and stability have cast a shadow over their potential wide-ranging applications. In this study, we present the synthesis of two lead-free all-inorganic perovskite materials, Cs3M2Br9 (where M = Bi or Sb), in bulk form, using an aqueous halide acid medium. Additionally, we describe a top-down approach for the fabrication of two lead-free all-inorganic perovskite, Cs3M2Br9 (M = Bi or Sb) NCs. The Cs3Sb2Br9 NCs display a sheet-like morphology, while Cs3Bi2Br9 NCs exhibit a cubic structure. The PL spectra of Cs3Sb2Br9 and Cs3Bi2Br9 NCs exhibit distinct emission peaks at 476 nm and 472 nm, respectively, with relatively narrow full width at half maximum (FWHM) of 44 nm and 38 nm, respectively. Cs3Sb2Br9 and Cs3Bi2Br9 NCs demonstrate excellent thermal stability up to 320 °C and 470 °C, respectively. Notably, the high photoluminescence quantum yield (PLQY) of these NCs, Cs3Sb2Br9 NCs (31 %) and Cs3Bi2Br9 NCs (36 %) are highly beneficial for optoelectronic applications is observed.

WITHDRAWN: Kinetics and mechanism of the reactions of alkanediamine-linked dinuclear platinum(II) complexes with some biorelevant-nucleophiles

The kinetics and mechanism of substitition reactions of dinuclear platinum(II) complexes of the general formula [{Pt(H2O)}2(N,N,N′,N′-tetrakis(2-pyridylmethyl)-N(CH2)n-N](ClO4)4,viz., n = 2 (PtEn); 3 (PtProp); 6 (PtHex); 8 (PtOct) and 10 (PtDec) were investigated in 0.10 M aqueous perchloric acid medium as a function of concentration of l-glutathione (Glu) and dl-penicilliamine (Pen) nucleophiles and temperature under pseudo first-order conditions using UV–visible spectrophotometry. The reactivity data of the dinuclear Pt(II) complexes were compared with those of their mononuclear analogues of the form [Pt(H2O)(N,N-bis(2-pyridylmethyl)-N(CH2)n-CH3](ClO4)2, n = 1 (Ptbpea); 2 (Ptbppa); 5 (Ptbpha) and 9 (Ptbpda) under the same experimental conditions. The observed rate constants for the substitution of the aqua ligands follow the simple rate law: kobs = k2[Nu]. The reactivity of the complexes increases as the chain length of the linker or tail increases except Prop which showed a higher reactivity towards the nucleophiles than the rest of the complexes. The overall trend of reactivity for the dinuclear platinum(II) complexes is PtEn < PtHex < PtOct < PtDec < PtProp. The reactivity of the mononuclear complexes follows the same trend as the dinuclears and increases in the order Ptbpea < Ptbppa < Ptbpha < Ptbpda. In all cases, the mononuclear complexes are more reactive than their dinuclear analogues, which is an indication of the steric retardation on the rate of substitution due to the conformations of the dinuclear platinum(II) complexes. Glu was found to be a better nucleophile than Pen. The relatively small and positive values for the enthalpy of activation, negative values for entropy of activation and the dependence of the second-order rate constants on the concentration of entering nucleophiles supports an associatively activated mechanism.

Curcumin-derivatives as fluorescence-electrochemical dual probe for ultrasensitive detections of picric acid in aqueous media

We are reporting the two curcumin derivatives, ferrocenyl curcumin (Fc-cur) and 4-nitro-benzylidene curcumin (NBC), as a probe through dual modalities, i.e., fluorescence and electrochemical methods, for the detection of nitro-analytes, such as picric acid (PA). The probes exhibited aggregation-induced enhanced emission (AIEE), and the addition of picric acid (PA) demonstrated good and specific fluorimetric identification of PA in the aggregated state. By using density functional theory (DFT), the mechanism of picric acid's (PA) interactions with the probes was further investigated. DFT studies shows evidence of charge transfer from curcumin derivatives probe to picric acid resulting into the formation of an adduct. The reduction of trinitrophenol (PA) to 2, 4, 6-trinitrosophenol was investigated utilizing a probe-modified glassy carbon electrode (GCE) with a good detection limit of 9.63 ± 0.001 pM and 41.01 ± 0.002 pM, respectively, for Fc-cur@GCE and NBC@GCE, taking into account the redox behavior of the probe. The applicability of the designed sensor has been utilized for real-time application in the estimation of picric acid in several water samples collected from the different source.

Copper corrosion inhibition in acidic aqueous media through tolyltriazole application: performance analysis

Tolyltriazole (TTA) is recognized as an effective copper corrosion inhibitor in cooling systems due to its low toxicity and versatile properties. With the increasing focus on sustainable development, the employment of compounds of this nature has become increasingly widespread, driving the search for environmentally responsible alternatives. In this context, the aim of this work was to evaluate the efficiency of a corrosion inhibitor formulated with TTA on copper specimens in HCl 0.1 mol L−1 medium. The samples were exposed to the corrosive electrolyte with inhibitor concentrations ranging from 0 to 20 ppm. Electrochemical methods, including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy were employed for corrosion monitoring. Overall, the results revealed that TTA behaves as a predominantly anodic inhibitor. Additionally, polarization curves demonstrated that within the Tafel region, the inhibitor adsorbs to the copper surface, following the Langmuir isotherm model. Regarding inhibitory effectiveness, the observed values ranged between 81.3 and 96.1%, while morphological analyses indicated the presence of nitrogen on the surface of the copper specimens after electrochemical tests, confirming the formation of a protective TTA film. In conclusion, this study highlights TTA's efficacy as a corrosion inhibitor, demonstrating its significant potential in safeguarding copper against acidic environments.

A Comparative Kinetic Study of Uncatalyzed and Ce(IV) Catalyzed Cetrizine Dihydrochloride Oxidation in Aqueous Acid Medium by Chloramine-T

A kinetic study of uncatalyzed and Ce(IV) catalyzed cetrizine dihydrochloride oxidation was carried out in aqueous acid medium using chloramine-T. Both uncatalyzed and catalyzed reactions follows first order kinetics with respect to [CAT] and fractional order kinetics with respect to [substrate]. The reaction follows first order dependence on [CeIV] catalyst. The uncatalyzed reaction shows inverse fractional order for [H+] and [Cl–] whereas catalyzed reaction follows fractional order. The effect of ionic strength is negligible in both cases. The dielectric constant has negative effect on uncatalyzed reaction and positive effect on catalyzed reaction. To compute the thermodynamic parameters the kinetic runs were studied at different temperatures (293-313 K). The stoichiometry of the reaction was studied and the products of oxidation were analyzed. The rate law was also derived by the proposed mechanism.

A novel cloud point back-extraction of uranium(VI) from organic radioactive solution to slightly acidic aqueous medium

ABSTRACT Stripping back uranium(VI) from an organic radioactive solution to an aqueous medium was rendered simple and quantitative by an unprecedented cloud point back-extraction (CPEback) method. The concentration difference of nitrate ions in and out of the micelle was employed to change the uranium distribution coefficient in favor of the bulk aqueous phase. In addition, the monophasic nature of cloud point extraction and the complexing ability of oxalic acid with uranyl ion in the bulk aqueous phase resulted in the quantitative recovery of uranium in a single step. The CPEback parameters were optimized through a cross-optimization process and the recovered uranium was quantified by the biamperometric titration method. The proposed analytical procedure resulted in high back-extraction efficiency and recovery of (99.6 ± 0.2)% and 99.2%, respectively. The process turned large volumes of organic radioactive solution into small volumes of a less hazardous organic medium having high viscosity and negligible vapor pressure. Analysis of two real samples of ~17 and 165 mL organic radioactive solutions resulted in 99% and 98.2% uranium recoveries, respectively. The leftover organic phase containing the extractant and nonionic surfactant can now be easily stored or reused.

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of a low-alloyed tempered martensitic steel submitted to high internal pressure

The influence of hydrogen on the mechanical behavior of a quenched and tempered 42CrMo4 steel has been evaluated by means of high internal pressure fracture tests carried out on hydrogen precharged notched cylindrical specimens. The notched cylindrical specimens were precharged for 3 h time with 1.2 mA/cm2 in two different aqueous media: 1 M H2SO4 added with 0.25 g/l As2O3 and 3.5% of NaCl solution. Hydraulic fracture tests were performed at different ramps of pressure: 7000, 220, 80, 60 and 30 MPa/h, respectively. Hydrogen damage was more marked when the acid aqueous medium (1 M H2SO4 + 0.25 g/l As2O3) was employed. In this case, a higher hydrogen concentration was introduced, leading to hydrogen decohesion micromechanisms (HEDE) near the notched region, especially when tests were performed at 60 MPa/h. Hydrogen embrittlement susceptibility is discussed in terms of the microstructural singularities and the operative fracture micromechanisms observed in each case.

Graft Copolymerization of Acrylonitrile onto Banana Cellulose Fiber

The graft co-polymerization of acrylonitrile monomer (AN) onto banana cellulose fiber (BCF) was carried out using ceric ammonium nitrate (CAN)/oxalic acid (OA) as redox pair in the aqueous nitric acid medium at 90 ºC. The effect of different reaction conditions on the grafting has been studied by determining the grafting parameters, i.e. concentration of acrylonitrile, ceric ammonium nitrate, oxalic acid, nitric acid, reaction time and temperature were carefully optimized to achieve the highest rate of grafting polymerization (RG), highest percent grafting yield (%GY) and grafting efficiency (%GE). All the reagents enhanced the RG%, GY% and %GE, with an increase of concentration up to a certain extent and then found to decline, except for the concentration of nitric acid. The grafting parameters were also increased with time/duration and temperature. The water retention value (WRV) of the grafted co-polymer was also measured. Activation parameters such as energy of activation (Ea), enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) can also be reported by using the Arrhenius plot. The evidence of grafting can also be predicted by the FTIR spectral analysis, moreover, the organic reaction mechanism has been proposed.

Degradation of Tolonium Chloride Dye by Phosphate Ion in Aqueous Acidic Solution: Kinetic Approach

The degradation of tolonium chloride (TC+) dye by phosphate ion (PO43-) in an aqueous acidic solution was studied using spectrophotometric analysis at 301 K, I= 1.0 M, [TC+]= 1.5 × 10-5 M, [H+]= 1.0×10-3 M, and ʎmax 600 nm. To determine the potency and rate of the reactant species, an aqueous acidic medium was employed. The reaction's direction and tendency were predicted using a thermodynamic analysis at an interval of 5.0 K and a temperature range of 301-321 K. Without the presence of intermediate complex/free atoms formation, a reaction that produced phenyl sulphoxide, phenylamine, and HPO32- as products of the reaction was obtained with a molar ratio of 1:1 for both reactants. First-order tolonium chloride reactivity was found in the reaction and first-order for the phosphate ion, resulting in a second-order reaction overall. The reaction process accelerated as the concentration of hydrochloric acid rose. The response time decreased with an increase in ionic strength concentration and added Ca2+ and Cl- did catalyze the reaction positively. A straight line that went through the origin was produced by plotting 1/ko vs PO43- concentration. The spectroscopic analysis showed no discernible shift from λmax of 600 nm. Additionally, an increase in temperature accelerated the reaction process. The reaction has a negative free energy change, G (-3.13–1.12 KJ/mol) which indicates that it is spontaneous and that the reactants have more free energy than that of the products. While the enthalpy of activation, H is positive and indicates that the reaction was endothermic and followed an associative path, the entropy of activation, S, is also negative (-7.45–1.10 KJ/mol), indicating that the reaction is less disordered. Due to the added ions catalysis and absence of free atoms during the course of the reaction, an outer-sphere mechanism was suggested for the reaction.

Corrosion of an Additively Manufactured Ti6Al4V Alloy in Saline and Acidic Media.

The present work aims to provide corrosion performance data for an additively manufactured Ti6Al4V alloy in saline and polluted environments. The as-received additively manufactured material underwent heat treatment at 850 °C for 3 h to transform the acicular α' microstructure into a lamellar α microstructure. Comparative corrosion assessments were conducted between the heat-treated substrates, the as-received condition, and a conventionally mill-annealed alloy. Potentiodynamic polarization experiments were carried out in saline (3.5 wt.% NaCl) and acid aqueous media ((NH4)2SO4 containing Harrison's solution). The corrosion performance of additively manufactured substrates matched or surpassed that of the conventional alloy in Harrison's solutions while remaining inferior in saline medium, despite forming a thicker passive film. Overall, the XY plane showed better corrosion performance, particularly after the elimination of the acicular α' martensite by the applied heat treatment. The results also suggested that the presence of the coarse β phase was beneficial in 3.5 wt.% NaCl solution and detrimental in Harrison's solutions, more so in acidified and fluorinated conditions.

Selective Recognition of Aromatic Amino Acids by a Molecular Cleft in Water

AbstractThe development of water‐soluble hosts for the selective recognition of aromatic amino acids is highly desirable and may serve as a tool to facilitate drug discovery and enable fabrication of sensors for point‐of‐care monitoring in the context of phenylketonuria disease. This paper presents the synthesis and characterization of a water‐soluble molecular cleft which is demonstrated to selectively bind aromatic amino acid guests over other amino acids in aqueous medium, favoring ʟ‐Trp over ʟ‐Phe and ʟ‐Tyr by a factor of approximately five. Host/guest‐interaction forces were studied by 1H‐NMR titrations complemented by fluorescence titrations and isothermal titration calorimetry. The here presented results provide a starting point for future optimizations in our efforts to selectively identify and quantify individual aromatic amino acids in aqueous medium.

Enhancing Electrocatalytic Synthesis of Glycine with CuPb1ML Electrode Synthesized via Pb UPD

AbstractIn the field of reductive organic electrosynthesis, the hydrogen evolution reaction (HER) is considered a parasitic reaction that lowers the Faradaic efficiency of the synthesis. Metals with a high overpotential for HER are often used to prevent this. However, this limits the catalytic materials that can be used in these reactions. To expand upon the scope of available electrocatalysts, we prepared a CuPb electrode via underpotential deposition (UPD). We thereby created an electrocatalyst with a single monolayer of Pb, CuPb1ML, in which Pb weight loading is only 415 ng cm−2, yet its properties could still effectively inhibit HER. The CuPb1ML electrode was used in the electrosynthesis of glycine from oxalic acid and hydroxylamine. This reaction served as a model for a C−N bond forming reaction in acidic aqueous media. The CuPb1ML electrode was compared against a pure Pb and Cu metal electrode. The CuPb1ML electrode showed a Faradaic efficiency for glycine production of 57 %, which was 9‐fold higher than Cu and rivaled the Pb electrode. The catalytic activity of CuPb1ML was 211 μmol h−1 cm−2, which is higher than both Cu and Pb. The mechanism of the electroreduction was then studied via in situ Fourier Transform Infra‐Red (FTIR) spectroscopy. These results hinted to an evolution of the electrocatalyst during the electrolysis reaction, which was then studied via Scanning Electron Microscopy (SEM) and X‐Ray Photoelectron spectroscopy (XPS). We found that the Pb monolayer restructured during catalysis, forming microparticles that were active in the reaction based on the listed experiments. Pb alloying into the lattice, which can occur during UPD, also lowered the HER, further facilitating glycine synthesis. Thus, our research also shows how Pb UPD impacts the catalytic properties of a metal both through monolayer deposition as well as surface alloying.

Investigation of the Effects of Different H2SO4, HCI, HNO3 and HCIO4 Liquid Acid Media on the Synthesis of CdTe Semiconductor Thin Films for Solar Cells

The main target of the present paper is to investigate the effect of different acidic aqueous media(DAAM) on the synthesis of cadmium telluride thin films(CdTeTFm). The synthesis of CdTeTFm was carried out by the electrochemical deposition method(EDM) in DAAM. The chronoamperometry method of electrodeposition(ED) was used for the production of CdTeTFm. Furthermore, the electrochemical behaviors of the solutions were studied using cyclic voltammetry. The experiments were carried out with 3 electrodes (a working electrode (WE), a reference electrode(CE), and a counter electrode(RE)) using the electrochemical cell potentiostatic method. The experimental conditions of the acidic aqueous CdTe solution have been determined to be pH 3.56-3.57, the temperature of the solution is 85°C, the concentration of CdTe 2.45x10-1 M, and the reaction time is 25 minutes. The physical properties of CdTeTFm were determined by XRD, SEM/EDX, FT-IR, and UV-VIS analysis methods. According to the results of the analysis, it was observed that acidic aqueous media have an important role in the synthesis of CdTeTFm. The bandgap ranges and Cd/Te ratios of the synthesized thin films were obtained as 1.42, 1.48, 1.50, 1.58 eV, 0.65, 0.587, 0.79 and 0.738, respectively.

Ortho-iodination of aromatic carboxylic acids in aqueous media

A straightforward method has been developed for Pd(II) catalyzed ortho-iodination of benzoic acids in aqueous media. In this paper, mono-iodination of benzoic acids is reported in the presence of KI as the iodine source.

Aggregation induced emission and volatile acid vapour sensing in acridine appended poly (aryl ether) based low molecular weight organogelator.

Considerable research attention has been devoted to the development of portable and rapid fluorescence sensors that can selectively detect volatile acids, due to the harmful effects of acid vapour on the environment and human health. Although various types of fluorophores have been reported for sensing volatile acid vapours, regulation of the sensory response using aggregation induced emissive (AIE) based gelators has rarely been reported. In this study, we present the design and synthesis of a novel organogelator that is capable of sensing volatile acids through AIE. An acridine-attached poly(aryl ether) dendron molecular system is synthesized through an aldimine coupling reaction, which self-assembles and forms a gel, exhibiting AIE behavior. The synthesized molecule and prepared gel were characterized using NMR, MASS, XRD, HRSEM and rheology techniques. The AIE property of APD was investigated using steady-state absorption and emission spectroscopic techniques. The sensory response of the APD gelator was tested with various analytes, and the results indicated that APD shows rapid response, particularly to acid vapours, where the detection limits (DL) of trifluoroacetic acid (TFA), hydrochloric acid (HCl) and nitric acid (HNO3) vapor were as low as 0.22, 0.9 and 0.30 ppm, respectively. An APD solid film in filter paper shows a visual color change from yellow to red in an aqueous acidic medium, and the effect is reversed in an alkaline medium. These findings suggest that an APD gelator could potentially be utilized to generate a portable acid vapor sensor kit due to its low detection limit and rapid response time, and it could be also be used as a substitute for existing acid indicators.

Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes.

Oxide-derived metals are produced by reducing an oxide precursor. These materials, including gold, have shown improved catalytic performance over many native metals. The origin of this improvement for gold is not yet understood. In this study, operando non-resonant sum frequency generation (SFG) and ex situ high-pressure X-ray photoelectron spectroscopy (HP-XPS) have been employed to investigate electrochemically-formed oxide-derived gold (OD-Au) from polycrystalline gold surfaces. A range of different oxidizing conditions were used to form OD-Au in acidic aqueous medium (H3PO4, pH = 1). Our electrochemical data after OD-Au is generated suggest that the surface is metallic gold, however SFG signal variations indicate the presence of subsurface gold oxide remnants between the metallic gold surface layer and bulk gold. The HP-XPS results suggest that this subsurface gold oxide could be in the form of Au2O3 or Au(OH)3. Furthermore, the SFG measurements show that with reducing electrochemical treatments the original gold metallic state can be restored, meaning the subsurface gold oxide is released. This work demonstrates that remnants of gold oxide persist beneath the topmost gold layer when the OD-Au is created, potentially facilitating the understanding of the improved catalytic properties of OD-Au.

Kinetics and oxidation of thiocarbohydrazide by hexacyanoferrate(III) in aqueous perchloric acid medium

Hexacyanoferrate(III) [HCF(III)] was used to oxidize thiocarbohydrazide (TCH) in an aqueous perchloric acid (HClO4) medium, and the reaction kinetics were studied spectrophotometrically at 420 nm while keeping a constant ionic strength of 1.0 mol dm−3 and modulating the temperature between 298K–318K. The stoichiometry of the reaction among TCH and HCF in the HClO4 medium is 1:2. The reaction has a lower than unit order in both TCH and HClO4 and is of the first order in HCF. The impact of varying the ionic strength and dielectric constant of the medium on the rate has been investigated. The effect of temperature on the reaction rate was studied, and different activation parameters of reaction Ea, ΔH#, ΔS#, ΔG#, and log10 A were calculated. The products of oxidation were analyzed by simple qualitative analysis. On the basis of the collected data, the rate law has been derived, and a probable mechanism has been proposed.

Degradation of poly(conjugated ester)s using a conjugate substitution reaction with various amines and amino acids in aqueous media

Degradation of poly(conjugated ester)s using a conjugate substitution reaction with various amines and amino acids in aqueous media