Sulfuric Acid Medium Research Articles

JUSTIFICATION OF ORDER OF CORROSION INHIBITION KINETICS FOR ESTERS OF CASTOR AND RUBBER SEED OILS

The present study centres on the justification of order of corrosion inhibition kinetics for esters of castor and rubber seed oils. Inhibition of mildsteel corrosion was studied in the presence of sulphuric acid medium. The study was justified by the regular misprediction of order of chemical reactions (especially corrosion reaction), due to varying individual perceptions in this regard. While many researchers assume that corrosion reaction kinetics is of first order in most cases, others resolve that it is of zero or even second order. Experimental (gravimetric) data from the mildsteel corrosion inhibition process was used to generate the kinetic data at different experimental conditions of 10g/l (concentration), 40oC (temperature) and 50% stroke (pressure), at different times of 4, 8, 16, 24 and 32hours. Equations of the lines were generated, and coefficient of determination, R2 values for the different (derived) kinetic equations (zero, first and second orders) were obtained. While R2 values for zero order curves fall between 0.9250 – 0.9790, those of first order fall between 0.9740 – 0.9880, and those of second order fall between 0.7820 – 0.9520, which indicates that the R2 values of first order kinetics tend more towards unity than those of zero and second orders. This implies that the corrosion reaction, generally, is governed by the postulations of first order kinetics, followed by the zero order and, then, second order. The results, therefore, justify that kinetics of corrosion reactions is (always) of first order. Keywords: Corrosion inhibition, Justification, Kinetics, Order of reaction.

Assessment of a Nigerian chalcopyrite ore dissolution in sulfuric acid medium

ABSTRACT. This paper presents a study of dissolution kinetics of a Nigerian chalcopyrite ore in sulfuric acid lixiviant. The effects of acid concentration, temperature and particle diameter on the dissolution rates of chalcopyrite ore have been examined. The dissolution rates are significantly influenced by increase in temperature, hydrogen ion concentration [H+], and decrease in particle diameter. The experimental data for the dissolution rate have been analyzed with the shrinking core model which shows the rate controlling step for the dissolution of chalcopyrite ore occurs via surface chemical solution. With 4 M H2SO4 solution, about 91.6% of 10 g/L chalcopyrite ore at 80 oC was dissolved within 120 min using -90+75 µm particle diameter. The reaction order with respect to hydrogen ion concentration was found to be 0.57 with correlation coefficient 0.968. The calculated activation energy, (Ea) value of 44.9 kJ/mol for the dissolution process was established. However, the SEM morphology of the residues from leaching process showed that about 8.4% of the initial solid material contained admixtures of Fukuchilite (Cu0.42Fe0.58S2), and elemental sulphur (So) and are formed around the shrinking core of the unreacted material.
 
 KEY WORDS: Chalcopyrite, Sulfuric acid, Dissolution kinetics
 
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 187-196. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.15

Indirect Spectroscopic Determination of Carvedilol and Propranolol Hydrochloride in Its Pure Form Using Methyl Orange Dye and Applying to Their Pharmaceutical Preparations

An easy, rapid, and indirect, selective spectroscopic method was developed for estimating Carvedilol and Propranolol in their pure form and in their pharmaceutical preparations, as the method relies on oxidation and reduction with a known increase (excess) of the oxidizing agent cerium sulfate ( in medium of sulfuric acid 5 molar) and estimation of the remaining of the oxidizing agent (surplus excess) by its reaction with methyl orange to form a pink color complex, the maximum absorption was given at the wavelength of 507 nm. The relationship was linear with in the ranges of concentration (0.5 - 24.5 and 0.5 - 24.0) μg / ml for carvedilol and propranolol respectively with molar absorptivity of 2.88 × 104 and 2.076 x 104 l. mol-1 . cm-1 and recovery rate of 99.54% and 99.42% respectively standard deviation value amounted to less than 0.37% for each one of the Carvedilol and Propranolol respectively in such a way that indicates good accuracy and compatibility. The method was successfully applied to the pharmaceutical preparations of the two drugs under study on the form of tablets, The results of the method are compatible with the original content of the pharmaceutical preparations and with the results of the standard addition method, there is no noticeable overlap of the excipient materials, that proves the efficiency of the proposed method.

Corrosion Inhibition and Adsorption Mechanism of PVP for Mild Steel in 1.0 M H2SO4: Experimental and Theoretical Approach

Aim:Corrosion of mild steel pipe line when exposed to dilute sulphuric acid is a very serious problem for people in the industry and they are in constant search of highly efficient corrosion inhibitors for acidic medium. For designing new corrosion inhibitors, a through knowledge of corrosion and adsorption mechanism is required.Background:Pitting, cracking and uniform types of corrosion are very common forms of corrosion in dilute sulphuric acid medium. A highly efficient acid corrosion inhibitor is required to minimize all these three forms of corrosion.Objective:The objective was to provide a solution for pitting, cracking, and uniform types of corrosion and to study corrosion and inhibition mechanisms so that highly efficient corrosion inhibitors can be designed.Methods:Polyvinyl pyrrolidone (PVP) was explored as a corrosion inhibitor for mild steel in 1.0 M H2SO4 by experimental and theoretical techniques. Experimental techniques used were impedance, weight loss, metallurgical microscopy, and polarization. Theoretical techniques used were DFT, MD simulation, Frontier molecular orbital, Langmuir, and Frumkin adsorption. Theoretical parameters like interaction energy, adsorption energy, Fukui function, chemical potential, electron density distribution, HOMO/LUMO eigenvalue, etc., help in understanding the mechanism of adsorption of PVP on the Fe (110) surface.Results:Experimental results were supported by theoretical studies. A linear relation was observed between PVP concentration and inhibition efficiency. A maximum of 85.92% inhibition efficiency was observed with a regression coefficient of 0.998. The pore length, the number of pits, and cracks intensity decrease with the concentration of PVP. The waste dilute H2SO4 after the weight loss study was investigated for its biocompatibility and was found to be within the acceptable limit.Conclusion:PVP was proved to be a highly efficient acid corrosion inhibitor for mild steel in 1.0 M H2SO4 medium.

Natural corrosion inhibitor of renewable eco-waste for SS-410 in sulfuric acid medium: adsorption, electrochemical, and computational studies

The petroleum pipeline corrosion is one of the biggest problems faced by oil industries. This investigation shows the corrosion resistance activity for SS-410 (stainless steel using in the petroleum pipeline), by varying the concentration of Piper nigrum leaves (PNL) extract. In this study, the effect of PNL extract for corrosion resistance of stainless steel (SS-410) mostly used in petroleum industries, coupons in 0.5 H2SO4, were analyzed by Potentiodynamic polarization (PDP) and Eletrochemical impedance spectroscopy (EIS) data. A potentiodynamic polarisation study revealed 94.20% inhibition efficiency of the PNL extract, at critical concentrations. Computational studies, using Density functional theory (DFT) and molecular dynamics (MD) simulation, were led as a valuable report for understanding the electronic adsorption, comparative inhibitory activities of phytochemicals. The Infrared (IR), Ultraviolet–visible (UV–vis) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and X-Ray Diffraction (XRD) findings indicate that the PNL extract is capable for preventing aggressive media from adhering on SS-410 surfaces.

Inhibition of corrosion of copper by polyvinylpyrrolidone-iodine in sulfuric acid medium

Inhibition of corrosion of copper by polyvinylpyrrolidone-iodine in sulfuric acid medium

Inhibition of corrosion of copper by polyvinylpyrrolidone-iodine in sulfuric acid medium

Inhibition of corrosion of copper by polyvinylpyrrolidone-iodine in sulfuric acid medium

An Experimental and Theoretical Investigation of the Efficacy of Pantoprazole as a Corrosion Inhibitor for Mild Steel in an Acidic Medium

The corrosion behavior of mild steel in a 1 M aqueous sulfuric acid medium in the presence and absence of the drug Pantoprazole was investigated using potentiodynamic polarization and quantum chemical calculations as well as Monte Carlo and molecular dynamic simulations. The potentiodynamic experiments indicated that this molecule, as a result of its adsorption on a mild steel surface, functioned as a mixed inhibitor. The goal of the study was to use theoretical calculations to acquire a better understanding of how inhibition works. The adsorption behavior of the examined compounds on the Fe (1 1 0) surface was calculated using a Monte Carlo simulation. Furthermore, the molecules were studied using density functional theory (DFT), especially the PBE functional, to determine the relationship between the molecular structure and the corrosion inhibition behavior of the chemical under research. The adsorption energies of Pantoprazole (in its three different protonation states) iron were calculated more precisely using molecular mechanics with periodic boundary conditions (PBC). The predicted theoretical parameters were found to be in agreement with the experimental data, which was a considerable help in understanding the corrosion inhibition mechanism displayed by this chemical.

Transmission Electron Microscopy Study on the Precipitation Behaviors of Laser-Welded Ferritic Stainless Steels and Their Implications on Intergranular Corrosion Resistance

The intergranular corrosion susceptibility of ferritic stainless-steel weldments is strongly dependent on chromium carbide precipitation phenomena. Hence, stabilization is widely used to mitigate the aforementioned precipitation. In contrast, stabilization has proved ineffective to fully prevent intergranular corrosion due to segregation of unreacted chromium during solid-state heat-treatments. To analyze the precipitation behavior of 17 wt.-% chromium ferritic stainless steels during laser welding, sheets of unstabilized and titanium-stabilized ferritic stainless steels were welded in a butt joint configuration and characterized with special consideration of precipitation behavior by means of transmission electron microscopy. While unstabilized ferritic stainless steels exhibit pronounced chromium precipitate formation at grain boundaries, titanium-stabilization leads to titanium precipitates without adjacent chromium segregation. However, corrosion tests reveal three distinctive corrosion mechanisms within the investigated ferritic stainless steels based on their inherent precipitation behaviors. In light of the precipitation formation, it is evident that immersion in sulfuric acid media leads to the dissolution of either grain boundaries or the grain boundary vicinity. As a result, the residual mechanical strength of the joint is substantially degraded.

A novel synergistic extraction system for the recovery of scandium (III) from sulfuric acid medium with mixed Cyanex923 and N1923

High extraction capability and outstanding selectivity are very attractive in the solvent extraction process. Scandium (Sc(III)), as a primary rare earth element (REE), generally lacks independent large-scale deposits and is mainly recovered as a by-product during the processing of mineral. However, the difficulty of stripping has been always a crucial problem to be solved in the scandium extraction system. This study aims to improve stripping performance while enhancing extraction efficiency for scandium. Herein, a novel synergistic extraction system for the recovery of scandium with a mixture of Cyanex923 (A, a mixture of four trialkylphosphine oxides) and N1923 (B, primary amine R1R2CHNH2) in sulfuric acid medium was put forward. The effect of the molar fraction (X) of Cyanex923 on the extraction of scandium was systematically investigated. The experimental results demonstrated that the coupled Cyanex923-N1923 exhibited an obvious synergistic effect on Sc(III). The maximum synergistic enhancement coefficient (Rmax) was calculated to be 2.20 when the molar fraction (X) of Cyanex923 was 0.4, and the H2SO4 concentration was 0.25 mol·L−1. Moreover, the synergistic extraction mechanism was discussed combined with multiple techniques including slope analysis method, FT-IR and NMR characterizations, to which the structure of extracted complexed was deduced to be Sc(SO4)1.5∙(A)0.5(B). Thermodynamic experiment was also explored in detail. More importantly, stripping with only 2 mol·L−1 HNO3 produced a relatively high stripping rate of 95%. The synergistic system still presented excellent reusability even after five treatment cycles. Finally, this study pointed out a potential industrial application value for the separation and recovery of Sc(III) from the sulfuric acid leaching liquor of nickel laterite ores.

Boron doped diamond electrode in analytical chemistry: methods of electrode surface activation (а short review)

The review is presents to the feature of the use of a boron doped diamond electrode (BDDE) in analytical chemistry. BDDE –one of the most modern material, which is widely used in analytical chemistry and bioanalytical chemistry, as well as for organic synthesis, cleaning of the environment from pollution, medicine, etc. BDDE is becoming increasingly popular for voltammetric determination of residual amounts organic substances in complex objects (medicines, biological fluids, food). Nowadays use rod (disk) and film BDDE. The advantage of film electrodes is their portability and compactness, which, in turn, allows them to be used for rapid analysis of biological fluids, when one drop of sample is enough for analysis. BDDE require surface cleaning and activation, as do other stationary electrodes. In this paper, the main attention is focused on the features of BDDE activation surface for use in the analysis. Activate the electrode surface potentiostatically, galvanostatically and under dynamic conditions. Аlso use different background electrolytes. BDDE is usually electrochemically treated in aqueous solutions, mostly the surface of the electrode is cleaned and activated at the same time. Proper pre-electrochemical treatment can be a valuable way to achieve improved analytical properties of the methods of voltammetric determination. In this case, оbtain a more intense analytical signal, a narrower, clearer peak and/or a useful shift of the peak potential, which increases the sensitivity and selectivity of the determination. For the most part, activation in a medium of sulfuric acid with a sufficiently high concentration of 0.5–1.0 M is chosen as the optimal one. The electrode is polarized alternately anode and cathode (regardless of the chemical structure of the analyte or the nature of the electrode process). However, the method of activation must always be chosen experimentally. The review contains more than 80 references on the features of BDDE surface activation, including monographs, reviews, articles and original works. Keywords: voltammetry, boron doped diamond electrode, activation surface polarization.

Recovery of copper and valuable metals from E-waste via hydrometallurgical method

Hydrometallurgical processes such as sulphuric acid leaching for recovering metal from waste from electrical and electronic equipment (WEEE), especially metal-rich printed circuit board (PCB), have provided a route for WEEE recycling. This study investigated the effect of the rate of oxidants (hydrogen peroxide) addition in volume per hour and temperature on the extraction of copper and other valuable metals from waste printed circuit board (WPCB). The optimum condition for the extraction of copper and valuable metal in sulphuric acid leaching were determined. The crushed and ground WPSB were leached in the sulphuric acid solution using hydrogen peroxide as an oxidant. The influence of two parameters; temperature (30 °C and 75 °C) and rate of oxidant addition (20 ml/hr and 60 ml/hr) were investigated against the extraction of copper (Cu, 30 wt%), aluminium (Al, 10.5 wt%), iron (Fe, 2.4 wt%), and zinc (Zn, 0.2 wt%). Scanning electron microscope-backscattered electron (SEM-BSE) image shows that shredding PCB into sizes smaller than 2.00 mm is sufficient to expose laminated copper components for an efficient sulphuric acid leaching process. The optimal condition for high extraction of copper was 1.5 M sulphuric acid, with 30 % hydrogen peroxide at rate 60 ml/hr, for ∼ 10 g of PCBs powder with a solid–liquid ratio of 1:10 for 1 h at temperature 75 °C.High percentage of extraction has been achieved in sulphuric acid media within 1 h (Cu (98 %), Al (52 %), Fe (52 %), Zn (92 %).

Effect of Cetyltrimethylammonium Bromide and Sodium Dodecyl Sulphate on Oxidation of Indigo Carmine with Potassium Peroxy Diphosphate: A Kinetic and Mechanistic Study

The oxidative kinetic study of Indigo carmine (IC) with potassium peroxydiphosphate (PDP) in absence and presence of cationic cetyl-trimethylammonium bromide (CTAB) and anionic sodium dodecyl sulphate (SDS) micelles was studied in an aqueous sulphuric acid medium by maintaining the ionic strength at 3.0 mol dm-3 using sodium sulphate. The pseudo-zero-order constant was determined from the linear plots of absorbance versus time under the conditions [IC] < [PDP]. The reaction obeys zero-order kinetics with respect to varying [IC], first order kinetics with respect to varying [H+] and [PDP] in the absence and in presence of micelles. The reaction rate was accelerated with varying [CTAB] and [SDS] and reached a limiting value. The [surfactant] rate profile has limited nature since the reaction is unimolecular on the micelle surface. The binding constant of peroxy diphosphate was also determined with CTAB and SDS micelles by applying Berezin equation for the kinetic pattern.

КИНЕТИКА НИТРОВАНИЯ М-НИТРОБЕНЗОЙНОЙ КИСЛОТЫ В ВОДНЫХ РАСТВОРАХ СЕРНОЙ КИСЛОТЫ

The kinetics of the nitration reaction of m-nitrobenzoic acid with nitric acid in a sulfuric acid medium of various concentrations was studied by UV spectroscopy. The observed differences in the rate of nitration of m-nitrobenzoic acid from the nitration of alkylbenzenes are associated with the electron-withdrawing nature of the carboxyl group, as well as with its protonation. During the reaction, not only 3,5-dinitrobenzoic acid is formed, but also products with significantly higher molar absorption coefficients

STUDY OF CATALYTIC OXIDATION OF SERINE BY CERIUM (IV) IN PARTIALAQUEOUS ACIDIC MEDIUM.

The oxidation of serine catalysed by cerium(IV) has been studied in sulphuric acid medium at 318 K. The reaction follows rst order kinetics with respect to [Mn(II)] while negative effect was observed for the variation of [H+] on the rate of reaction. The reaction exhibits rst to zero order kinetics with respect to serine at its lower to higher concentrations. Under the experimental condition, the kinetically active species of cerium(IV) has been found to be Ce(SO4)2. Activation parameters has been calculated. The mechanism has been proposed from the results of kinetic studies, reaction stoichiometry and product analysis.

Evaluation of Corrosion inhibition properties of pharmaceutically active compound Cefotaxime sodium on mild steel surface in sulfuric acid medium

Cefotaxime sodium is applied in various concentrations in 0.5M sulphuric acid towards the mild steel and analyzed through weight loss, potentiodynamic polarization and EIS studies at 298 to 338oK. It gives good inhibition activity at lower temperature. Activation parameters, Gibbs free energy, Enthalpy and entropy of the reaction has been calculated and found that the inhibition process follows physical adsorption on the surface. Adsorption process follows langmuir’s adsorption isotherm. The inhibition behavior on mild steel surface is supplemented by the surface study through atomic force microscopy and found that the inhibited surface have less roughness than the uninhibited surface.

Synthesis of Ag nanoparticles from waste printed circuit board

The amount of waste from electrical and electronic equipment has been growing every year. The printed circuit boards contained in this waste include metals that can be recovered through urban mining, adding value to this waste and minimizing environmental impacts with its incorrect disposal or treatment. In this work, memory boards obsolete with 0.053 wt% Ag were used. The extraction of all metals studied (Ag, Al, Cu, Fe, Ni, Sn, and Zn) involved the evaluation of the Pourbaix and speciation diagrams to identify the pH and redox potential conditions, considering the possible species formed with leaching agents: sulfuric, nitric, and hydrochloric medium. After the definition of the leaching agent, the extraction routes by hydrometallurgical processing were proposed from the parameters of temperature, s/l ratio, and reaction time previously studied. Route A was composed of sequential stages (the first leaching in a sulfuric medium and the second in an oxidizing sulfuric medium) and obtained 100% of Ag recovery. Route B consisted only of leaching in an oxidizing sulfuric medium, obtained about 94% of the Ag recovery, and could not contribute to the subsequent purification steps (if necessary) of this solution, as all metals would also be in the solution. These two routes showed that Ag can only be recovered in an oxidizing sulfuric acid medium, according to the conditions studied. Ag recovered in the leach liquor of the second stage of Route A was purified by chemical precipitation with NaCl, and the AgCl was solubilized in an NH4OH solution. This solution was used to synthesize silver nanoparticles by the Turkevich method in 25 min. The spherical nanoparticles synthesized an average size distribution of 67 nm.

Insight into the anti-corrosion performance of two food flavors as eco-friendly and ultra-high performance inhibitors for copper in sulfuric acid medium

2,5-dihydroxy-1,4-dithiane (DDD) and 2,5-dimethy- [1.4] dithiane-2,5-diol (DTDD) two food flavors as environmentally-friendly inhibitors for Cu in 0.5 mol/L H2SO4 media were researched via theoretical calculation and experimental ways. Electrochemical measurement data showed that DDD and DTDD can exhibit high level anti-corrosion feature. The anti-corrosion efficiency of DDD and DTDD were as high as 99.6% and 98.9%, respectively. The atomic force microscope (AFM) and scanning electron microscope (SEM) tests showed that the Cu specimens were immersed in the H2SO4 with 5 mM DDD and DTDD for 30 h at the 298 K, and the Cu specimen surface was still smooth. Besides, the adsorption of DDD and DTDD at the interface of Cu/solution was comply with Langmuir adsorption. Theoretical calculation data showed that DDD exhibit more ascendant anti-corrosion feature than DTDD.

SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF SOFOSBUVIR AND DACLATASVIR IN PURE AND DOSAGE FORMS

Objective: Two simple, sensitive and accurate spectrophotometric methods have been developed for the determination of sofosbuvir (SOF) and daclatasvir (DAC) in pure forms and pharmaceutical formulations. Methods: The proposed methods are based on the oxidation of SOF and DAC by a known excess of cerium(IV) ammonium nitrate in sulphuric acid medium followed by determination of unreacted cerium(IV) by adding a fixed amount of indigo carmine (IC) and alizarin red S (ARS) dyes followed by measuring the absorbance at 610 and 360 nm, respectively. The experimental conditions affecting the reaction were studied and optimized. Results: The beer’s law was obeyed in the concentration ranges of 0.2-3.0, 0.2-4.0 for SOF and 0.5-4.5 and 0.5-5.0 μg/ml for DAC using IC and ARS methods, respectively with a correlation coefficient ≥ 0.9991. The calculated molar absorptivity values are 2.354 × 104, 1.933 × 104 for SOF and 1.786 × 104 and 2.015 × 104 L/mol. cm for DAC using IC and ARS methods, respectively u. The limits of detection and quantification are also reported. Intra-day and inter-day precision and accuracy of the methods have been evaluated. Conclusion: The methods were successfully applied to the assay of SOF and DAC in tablets and the results were statistically compared with those of the reference method by applying Student’s t-test and F-test. No interference was observed from the common tablet excipients. The accuracy and reliability of the methods were further ascertained by performing recovery studies using the standard addition method.

NEW CORROSION INHIBITORS BASED ON AMINES AND AMIDES

In this work, new inhibitors of metal corrosion in sulfuric acid media are investigated depending on the duration of the process, inhibitor concentration and temperature. The main parameters of the synthesis of new corrosion inhibitors for metals of grade St.3 and St.12 with the use of amine and amide-containing organic substances have been determined, and methods for preparing these inhibitors have been described. The physicochemical properties of amine and amide containing organic inhibitors of corrosion and salt deposition in acidic process media have been studied.