Dissolution properties of oxymatrine in citric acid solution

In this article, the enthalpy of dissolution for oxymatrine in 0.15 M citric acid solution is measured using a RD496-2000 Calvet Microcalorimeter at 36.5 °C under atmospheric pressure. The differential enthalpy (Δ _dif H _m) and molar enthalpy (Δ _sol H _m) were determined for oxymatrine dissolution in 0.15 M citric acid solution. On the basis of these experimental data and calculated results, the kinetic equation, half-life, Δ _sol H _m, Δ _sol G _m, and Δ _sol S _m of the dissolution process were also obtained.     

Dissolution kinetics of silver metal nanoparticles in their reaction with nitric acid in an reverse micelle solution of AOT

The dissolution of silver nanoparticles in their reaction with aqueous HNO₃ solubilized to an reverse micelle solution of sodium bis(2-ethylhexyl)sulfosuccinate in decane is studied spectrophotometrically. A physicochemical model is advanced for quantifying the process kinetics on th basis of the following autocatalytic scheme: Ag⁰ + H⁺ + NO ₃ ^? → Ag⁺ + products (k ₁), and Ag⁰ + Ag⁺ + NO ₃ ^? → 2Ag⁺ + products (k ₂). The effective rate constant k ₂ decreases with decreasing solubilization capacity V _S/V _O (where V _S is the volume of the solubilized dispersed aqueous phase and V _O is the volume of the micelle solution); the solubilization capacity determines the size of the micelle cavities in which the reaction between Ag⁰ and HNO₃ occurs: k ₂ = 74 (V _S/V _O) · 100% ≈ 3.8%), 41 (2.9), and 35 (2.0) L/(mol s). The effective constant k ₁ is determined with a high uncertainty; the effect of V _S/V _O on k ₁ has the opposite tendency.     

Adsorption of benzotriazole on copper surfaces in a hydrochloric acid solution

The adsorption of benzotriazole (BTA) on commercial copper surfaces in hydrochloric (HCl) acid concentrations from 1 × 10^?3 to 5 × 10^?1 M was investigated using gravimetric measurements. BTA in bulk solution was tested in concentrations from 1 × 10^?5 to 1 × 10^?1 M at temperatures from 298 to 328 K. The adsorption mechanism is discussed using the objective function (OF) and in terms of applicability of the conventional isotherm models. The best fit was obtained using the Frumkin equation. The projected molecular area of BTA was calculated to elucidate inhibitor orientation in the adsorption process. Copyright © 2006 John Wiley & Sons, Ltd.     

Adenosine as corrosion inhibitor for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - (2R,3R,4S,5R)-2-(6-amino-9H-purin-9-yl)-5-(hydroxymethyl)oxolane-3,4-diol (adenosine) is an identified component present in agarwood leaf extract. The corrosion...     

Chemiluminescence accompanying chitosane destruction in hydrochloric acid solution containing hydrogen peroxide

The chemiluminescence (CL) accompanies the destruction of chitosane (CTS) in the presence of H₂O₂. The CL kinetics has a complex character and can be described as a sum of two exponentials. The photoluminescence monitoring and IR spectra of the reaction mixture indicate the formation of carbonyl groups in the course of CTS destruction. The enhancement of the CL intensity by Fe²⁺ suggests the reaction of Fe²⁺ with hydroperoxides accumulated with CTS decomposition. The macroradicals ROO^· are assumed to be transformed through the cleavage of the glycoside bond via a six-membered cyclic intermediate to form the terminal peroxide radical and ketone.     

A study of dissolution kinetics of a Nigerian galena ore in hydrochloric acid

The results of experimental investigation on the study of dissolution kinetics of a Nigerian galena ore in hydrochloric acid solution were discussed. The influence of acid concentration, temperature, particle size, stirring speed and solid/liquid ratio on the extent of dissolution was examined. The elemental analysis by XRF showed that the galena ore is composed mainly of PbS with metals such as Sn, Fe and Zn occurring as minor elements and Mn, Rb, Sr and Nb as traces. The XRD analysis indicated galena as the dominant mineral phase, with the presence of associated minerals, such as α-quartz (SiO₂), sphalerite (ZnS), cassiterite (SnO₂), pyrite (FeS₂) and manganese oxide (MnO₂).Results of leaching studies showed that galena dissolution in HCl solution increases with increasing acid concentration and temperature; while it decreases with particle diameter and solid/liquid ratio at a fixed stirring rate of 450 rpm. The study showed that 94.8% of galena was dissolved by 8.06 M HCl at 80 °C within 120 min with initial solid/liquid ratio of 10 g/L. The corresponding activation energy, E_a was calculated to be 38.74 kJ/mol. Other parameters such as reaction order, Arrhenius constants, reaction and dissociation constants were calculated to be 0.28, 73.69 s^?1, 1.73 ± 0.13 × 10³ and 1.37 ± 0.024 × 10⁴ mol L^?1 s^?1, respectively. The mechanism of dissolution of galena was established to follow the shrinking core model for the diffusion controlled mechanism with surface chemical reaction as the rate controlling step for the dissolution process. Finally, the XRD analysis of the post-leaching residue showed the presence of elemental sulphur, lead chloride and α-quartz.     

Kinetic investigation of the reaction of pertechnetate with thiourea in a hydrochloric acid solution

Reactions of pertechnetate ion with thiourea (tu) in a hydrochloric acid solution have been investigated by spectrophotometry. Two consecutive reactions were observed for the formation of a technetium-thiourea complex. The intermediate is considered to be a Tc(V)-tu complex ([TcO(tu)₄]³⁺). The observed reaction rates of these two reactions were found to be second order with respect to the concentration of thiourea. The rate-determining step in the 1st step was concluded tobe the reduction of Tc(VII) to Tc(V) and that in the 2nd step to be the reduction of Tc(V) to Tc(III).     

Electrochemical study of the degradation kinetics of polyaniline powder in sulfuric and hydrochloric acid media

Investigation of the degradation kinetics of polyaniline (PANi) powder has been performed with a cavity microelectrode in sulfuric and hydrochloric acid electrolytes using cyclic voltammetry. It was shown that the overall degradation mechanism is limited by first-order reaction kinetics. The rate constant of the polymer hydrolysis was found to be lower than the one determined for thin films. The influence of the electrolyte concentration was also investigated and compared with our previous work on the use of PANi as a battery material. Electronic Publication     

Synthesis of hydrochloric acid solution for total mercury determination in natural waters

Total mercury (Hg_T) determination requires the addition of concentrated hydrochloric acid solution (≥10 mol L⁻¹ HCl) in relatively high amounts to preserve the samples and to prepare reagent solutions. A method for the preparation of concentrated HCl with Hg_T concentration of lower than 5 ng L⁻¹ is described in this article. It is based on the well-known chemical reaction: 2 NH₄Cl + H₂SO₄ → (NH₄)₂SO₄ + 2 HCl. This method is validated thanks to the US Environmental Protection Agency method 1631 and standard reference materials BCR-579 (mercury in coastal seawater).     

Corrosion inhibition performance of tannins for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - The corrosion inhibition behavior of commercial hydrolysable tannin (tara tannin), condensed tannin (black wattle tannin) and complex tannin (bayberry tannin)...     

Study of the corrosion products formed on carbon steel surface in hydrochloric acid solution

Effect of an antibacterial drug, sulfacetamide, IUPAC name N-[(4-aminophenyl) sulfonyl] acetamide (APSA), on the corrosion products formed on carbon steel surface in 1.0?mol?L^?1 HCl solution has been investigated using mass loss, X-ray photoelectron spectroscopy (XPS), and simultaneous thermal and differential scanning calorimetry/differential thermal analysis (TG/DSC/DTA). Mass loss measurements reveal that the corrosion rate of carbon steel is retarded by APSA and that the inhibition efficiency of this inhibitor increases with increasing the concentration. XPS analysis shows that, at this stage, the main product of corrosion is a non-stoichiometric Fe³⁺ oxyhydroxide, consisting of a mixture of FeO(OH) in anhydrous or hydrated forms, containing Cl^? inclusions and adsorbed APSA molecules. The mechanism of inhibition was discussed in light of the chemical structure of the investigated inhibitor. The corrosion products were analyzed using TG/DSC/DTA technique.     

Phenyl semicarbazide derivatives as corrosion inhibitors for aluminium in hydrochloric acid solution

Summary Measurements of the corrosion rate of aluminium in 2N HCl at 27°C with and without addition of phenyl semicarbazide derivatives (10^–3–10^–5 mol/l) were performed. The adsorption of these compounds was elucidated. Results show that phenyl semicarbazide derivatives are adsorbed on the aluminium surface according to the Frumkin isotherm. From the adsorption isotherm some thermodynamic data for the adsorption process (G° _ads . andf) are calculated and discussed.

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Phenylsemicarbazide als Korrosionsinhibitoren für Aluminium in salzsauren Lösungen

Zusammenfassung Es wurden Messungen der Korrosionsgeschwindigkeit von Aluminium in 2N HCl bei 27°C mit und ohne Zusatz von Phenylsemicarbaziden (10^–3–10^–5 mol/l) durchgeführt. Es wurde die Adsorption dieser Verbindungen untersucht, wobei sich zeigte, daß die Adsorption der Phenylsemicarbazidderivate der Frumkin-Isotherme gehorcht. Aus der Isotherme wurden einige thermodynamische Parameter des Adsorptionsprozesses (G° _ads. ,f) berechnet.

     

Surface modification in natural fluorapatite after uranyl solution treatment

Natural fluorapatite samples were contacted with uranyl nitrate solutions (from 10⁻² to 10⁻⁶M), adjusted to pH 6.0, then, shaken for times varying between 15 minutes to 72 hours, at room temperature. After that, the solid and liquid phases were separated by centrifugation and the solid was dried at 80°C overnight. The uranium analysis of the solid samples and solutions revealed that uranium was incorporated over fluorapatite. Selected solid samples produced by contacting treatments were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XRD patterns showed the growth of uranyl species in the fluorapatite. Imaging by SEM at 20000x showed the location of uranyl compounds in a crystalline layer in the surface of fluorapatite grains. This layer was well defined for the 10⁻² M of U-contacting solution, but a saturation value was attained at 64% of uranium uptake yield. In the case of 10⁻⁴ M and lower U-contacting solution, the uranium uptake yield was near of 90% after 45 minutes. This fact suggests that natural fluorapatite has excellent properties to immobilize uranium compounds in a solution. Afterwards, the pregnant fluorapatite mineral was regenerated using an alkaline-leaching process. The uranium separated in this way is concentrated and can be handled to a final disposition.     

Inhibitive effect of chloroquine towards corrosion of mild steel in hydrochloric acid solution

Corrosion inhibition of mild steel (MS) by chloroquine (CQ) in 1 M HCl was investigated using weight loss, polarization, electrochemical impedance spectroscopy (EIS) and quantum chemical techniques. The inhibitor showed 99 % inhibition efficiency at concentration of 3.1 × 10^?4 M. Polarization studies showed that CQ is a mixed-type inhibitor. Adsorption of inhibitor molecules on the MS surface showed Langmuir adsorption isotherm. Thermodynamic parameters led to the conclusion that adsorption is predominantly chemisorption. Quantum chemical calculations were carried out to investigate the corrosion-inhibiting property of CQ. Various parameters such as energy of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), softness of molecule, Mullikan charges on various atoms and number of electrons transferred from inhibitor molecule to metal were calculated and correlated with the inhibiting property of CQ.     

Inhibiting effects of benzamide derivatives on the corrosion of mild steel in hydrochloric acid solution

The inhibition effect of new heterocyclic compounds, namely N-(cyanomethyl)benzamide (BENZA) and N-[(1H-tetrazol-5-yl)methyl]benzamide (BENZA-TET), on mild steel corrosion 1 M HCl was investigated using electrochemical measurements. The results indicated that the inhibition efficiency depends on concentration, immersion time and temperature. The BENZA is a better inhibitor than BENZA-TET. Polarization measurements showed that the inhibitor BENZA-TET is a cathodic type, but BENZA acts as a mixed type inhibitor. In addition, the changes in impedance parameters indicated that these compounds adsorbed on the metal surface leading to the formation of a protective film. Adsorption of benzamide derivatives on the mild steel surface was investigated to consider basic information on the interaction between the inhibitors and the metal surface. It was found to obey the Langmuir adsorption isotherm. From the temperature dependence, the activation energy in the presence of (BENZA) was found to be inferior to that in uninhibited medium. In order to explain why BENZA is the most efficient inhibitor, quantum chemical calculations were applied. The relationships between quantum chemical parameters and corrosion inhibition efficiency have been discussed to see if there is any correlation between them.     

Polycondensation kinetics of orthosilicic acid in a hydrothermal solution

The polycondensation kinetics of orthosilicic acid in hydrothermal solutions was studied experimentally at different temperatures, pH, and ionic strengths. As a result of the mathematical processing of experimental data, equations approximating the time dependence of the polycondensation process and the dependence of the polycondensation rate constant on the solution ionic strength were obtained. Experimental data on the kinetics of the reverse process of dissolving colloidal silica were obtained at different temperatures and pH.     

Isolation of an oxychloroniobium(IV) complex from hydrochloric acid solution

Summary An oxychloroniobium(IV) complex was isolated for the first time by zinc reduction of NbCl₅ in concentrated HCl solution. The product, an extremely moisture- and air-sensitive, intense blue solid was assigned a dimeric structure (H₃O)₂[Nb₂O₂Cl₆] based on elemental analysis, i.r. and u.v.-vis spectroscopy as well as magnetic and conductometric measurements.     

Extraction of platinum metals from hydrochloric acid medium with triphenylphosphine solution in 1,2-dichloroethane

Extraction of platinum metals with TPP in 1,2-dichloroethane from hydrochloric acid medium has been examined. At hydrochloric acid concentrations higher than 6M, palladium, platinum and osmium are extracted, whereas at low acidity only palladium is quantitatively extracted. Addition of stannous chloride as labilizing agent makes possible a group separation of platinum metals (except osmium). Possible extraction mechanisms are discussed.     

Effect of Avogadro natural oil on the corrosion inhibition of mild steel in hydrochloric acid solution

The inhibition action of Avogadro natural oil on corrosion of mild steel in one molar hydrochloric acid solution was investigated by gravimetric and potentiodynamic polarization techniques. The surface morphology of as-corroded samples was assessed with high resolution scanning transmission electron microscopy equipped with energy dispersive spectroscopy (HR-STEM/EDS). From the results, the presence of Avogadro natural oil in the metal–acidic interface decreased the corrosion rate with all the exposure times. The inhibition efficiency (%IE) increases with the concentration of the inhibitor considered. Results obtained from gravimetric measurements indicate that the natural oil exhibited higher efficiencies of 93.26 % after 384 h of exposure time and 98.26 % recorded in the potentiodynamic polarization method, both at 4.5 g/v inhibitor addition. Equally, results from the linear polarization indicated higher potential value with an increase in the polarization resistance (R _p) and lower current density for the inhibited samples than the uninhibited mild steel sample. The inhibitive effect of this oil was explained in view of adsorption on the metal surface. The adsorption process follows the Langmuir adsorption isotherm.