Hydrochloric Acid Solution Research Articles

Ricinus communis leaves extract as a green corrosion inhibitor for carbon steel in hydrochloric acid solution

The eco-friendliness of Ricinus communis leaves extract as an inhibitor for carbon steel (CS) corrosion was evaluated using weight loss (WL) as a chemical technique, and some electrochemical methods like AC electrochemical impedance spectroscopy (EIS), Tafel polarization (PP), and electrochemical frequency modulation (EFM). The data acquired showed that the higher the dose of the extract, the higher the protection efficiency (% IE), which increases with increasing temperature from 80.5 at 25 °C to 91.4 % at 45 °C. Using adsorption isotherms, adsorption factors were determined. Activation parameters were calculated and discussed based on Arrhenius and transition state principles. The adsorption procedure of Ricinus communis leaves extract on CS surface was found to be spontaneous and follows Langmuir's isotherm. This extract is a mixed type according to polarization data. Based on EIS data, it was shown that the extract of Ricinus communis leaves decreased the capacitance double layer (Cdl) from 539 to 74 μF cm−2 while enhancing the charge transfer resistance (Rct) from 70 to 430.5 Ω cm2. Surface analysis was done using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) to measure the degree of surface roughness, film formation, and adsorbed groups on the CS surface. According to these tests, a layer of extract molecules forms on the CS surface.

Using of Extracted Tannin from the Bark of Gray Avicennia Marina (Avicennia Marina) and Cordia Myxa (Cordia Myxa) Trees as Corrosion Green Inhibitors for Carbon Steel Alloy in Acidic Media.

This study evaluated the corrosion inhibiting properties of natural tannins extracted from gray Avicennia marina bark and Cordia myxa bark for carbon steel alloys. Such alloys are widely used in shipbuilding construction where corrosion poses challenges. Tannin extracts were tested as green inhibitors across varying concentrations in 0.5 M hydrochloric acid solution, a corrosive medium. Trials were conducted at different temperature parameters to determine the inhibition efficiencies. The amount of hydrogen gas released over time was quantified to compare corrosion rates in the absence and presence of tannin inhibitors. The Langmuir and Freundlich isotherm models for adsorption were also studied, as well as the kinetic and thermodynamic functions, where the change in free energy and activation energy were calculated. The results of the study showed a promising possibility to use the compounds under study as corrosion inhibitors for carbon steel with high efficiency up to more than 83% at a temperature of 25 degrees Celsius. The results showed an increase in the free energy change (ΔGcorro) values for the corrosion reaction in the presence of the inhibitors under study compared to corrosion in the absence of inhibitors, The free energy change (ΔGcorro) values at 25 degrees Celsius were (184.4538, 184.9246, 111.9616) kJ.mol-1 in the presence of the Avicennia marina inhibitor, Cordia myxa inhibitor and blank) consecutively. As a result, the speed of the corrosion reaction will decrease in the presence of inhibitors.

Synthesis and cyclic voltammetric studies of azo dye compounds derived from 1,5-dihydroxynaphthalene and their application as corrosion inhibitors for carbon steel in hydrochloric acid solution

New bis-azo dyes derived from 1,5-dihydroxynaphthalene were synthesized and characterized by elemental analysis, Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). These compounds were examined using differential pulse polarography (DPP) and cyclic voltammetry (CV) in Britton-Robinson buffer solutions with pH values ranging from 2 to 12. When the two NN centers of the examined azo compounds were cleaved to form the amine group, the bis-azo group was reduced with the loss of eight electrons, resulting in an irreversible diffusion-controlled cathodic peak. The reduction mechanism was postulated in view of the data obtained was found to be H+, e, e, H+. The application of these azo compounds as corrosion inhibitors for carbon steel in hydrochloric acid solution was investigated and the inhibition efficiency was found to be increasing with both time and concentration, reaching 97 % after 24 hours in the presence of 10−3 M for the three azo compounds. The Langmuir adsorption isotherm indicates that the suppression of corrosion is caused by the inhibitor molecules donating electrons to the empty d-orbitals of the surface of the carbon steel (chemical adsorption), as the calculated Gibbs free energy (∆Gads) is found to be around −40 kJ/mol. The influence of temperature on the parameters of corrosion was examined, and the thermodynamic parameters of corrosion were computed and examined. The results showed that increasing temperature causes increasing of the inhibition efficiency of the tested bis-azo dyes. The order of inhibition efficiency followed their donating affinity which increases in the order p-OCH3 > p-CH3 > m-CH3. Also, the results showed that these compounds causes decrease in entropy, enthalpy and activation energy due to their chemical interaction with the metal surface.

225Aс/213Bi generator for direct synthesis of 213Bi-labeled bioconjugates

Background213Bi is a short-lived radionuclide currently trialed for alpha therapy of various oncological diseases. A serious obstacle to the wide medical use is decay losses of 213Bi during a conventional synthesis of radiopharmaceuticals. In this work, we aimed to develop a two-column 225Aс/213Bi generator providing the accumulation of 213Bi separately from the parent 225Ac via continuous circular separation and decay of intermediate 221Fr. When attaining the transient equilibrium, 213Bi could be promptly extracted from the generator with an appropriate complexing agent, including chelator-protein bioconjugates. MethodsSorption behavior of Bi(III) ions onto the cross-linked dextran gel Sephadex G-25 was studied from solutions of hydrochloric and nitric acid, and from sodium chloride, sodium acetate and DTPA solutions. A bifunctional chelating agent p-SCN-Bn-DTPA was conjugated to an antibody Nimotuzumab specific to the epidermal growth factor receptor, and the procedure of 207,213Bi-DTPA-Nimotuzumab synthesis in the dextran gel medium was developed. The parameters of 225Aс/213Bi generator system were evaluated. ResultsThe weight distribution ratios of Bi(III) adsorbed onto the Sephadex G-25 gel were obtained. Up to 85 % of 213Bi was accumulated in the second Sephadex-filled column of 225Aс/213Bi generator after four-hour circulation of 0.15 M NaCl (pH 5.5) solution. Having passed the solution of DTPA-Nimotuzumab bioconjugate through the second column, a fraction of 213Bi-DTPA-Nimotuzumab radioimmunoconjugate was produced with the radiochemical yield of 64 % ± 3 % (n = 6). High radionuclidic and radiochemical purity of product was achieved. ConclusionsThe circulating 225Aс/213Bi generator provides a 213Bi-labeled bioconjugate as a final product. While a conventional synthesis route including generator milking, bioconjugate labeling and size-exclusion purification takes >20 min, the duration of 213Bi-DTPA-Nimotuzumab production by the method proposed in this work is reduced to 6–8 min.

Effects of Different Pre-Treatments on Local Pineapple Leaf as a Potential Substrate for the Production of Value-Added Products

Lignocellulosic biomass such as pineapple leaves can be applied as substrates in various biochemical processes such as solid-state fermentation to produce industrially important enzymes or other value-added products. However, recalcitrant nature of the biomass hinders the accessibility of cellulose for enzymatic hydrolysis in yielding high amounts of the intended products. In order to overcome this obstacle, pre-treatment is necessary as to loosen the lignocellulose structure to ease accessibility of enzymes and biodegradability of the biomass. In this study, local pineapple leaves were subjected to different methods of pre-treatments which are thermal pre-treatment by autoclaving, and chemical pre-treatments involving treatments with alkaline solutions (1% and 1.5% (w/v) sodium hydroxide) as well as acid solutions (1% and 1.5% (v/v) hydrochloric acid). Scanning Electron Microscopy was conducted to compare and study the effect of different pre-treatments on morphological changes of raw and pre-treated leaves. The obtained results revealed that the biomass was severely affected by 1.5% (v/v) hydrochloric acid solution as the surface structure was vigorously ruptured and more aggregated cracks were clearly visible in most parts, compared to the surface morphologies observed on raw samples and samples with other pre-treatment methods.

Study of the Dissolution of Tahoua Natural Phosphate by Mineral Acids: Hydrochloric Acid and Sulfuric Acid

The transformation of natural phosphorus into plant nutrient phosphorus, natural phosphates from Tahoua were dissolved in mineral acids, hydrochloric acid and sulfuric acid. Dissolution was effected at various concentrations (0.01M; 0.1M and 1M) and stirring times (1 hour, 3 hours and 5 hours). The results show that for all two acids (2), the dissolution rate is greater in concentrated acid solutions (1M) and for the 5-hour attack time. These rates are 38.37% and 34.87% respectively for sulfuric and hydrochloric acid solutions. Dissolution of Tahoua natural phosphate depends on the concentration of etching solutions and the etching time. With mineral acids (sulfuric and hydrochloric acid), for example, it increases with concentration. This dissolution offers interesting visions for perfecting phosphate fertilizers.

Optimization of waste biomass demineralization through response surface methodology and enhancement of thermochemical and fusion properties

This study examines the impact of leaching with dilute hydrochloric acid solution on the reduction of ash content and the thermal degradation behavior of sugarcane bagasse. Response surface methodology (RSM) was used to statistically design the experiments and investigate the effect of three independent variables: treatment time, solid-to-liquid ratio, and reagent concentration. The leaching conditions were further optimized and experimentally validated for maximum ash reduction for suitability of treated biomass as feedstock for thermochemical conversion technologies. Reagent concentration and treatment time directly affected ash reduction, while the solid-to-liquid ratio inversely influenced it. Concentration had the highest impact, and treatment duration had the least. The maximum 78.2% ash reduction was achieved by treating the biomass with 1 M HCl for 80 min at a solid-to-liquid ratio of 50:1 (wt/vol). This ash reduction also resulted in a 9.82% increase in higher heating value (HHV). Hemicellulose hydrolysis during leaching was observed through chemical composition and Fourier-transform infrared spectroscopy (FTIR). Ash fusion temperatures increased, indicating more thermally stable biomass. Thermogravimetric analysis (TGA) showed elevated maximum degradation temperature and activation energy.

Promising corrosion resistance of mild steel, copper, and aluminum in hydrochloric acid solution using an environmentally friendly corrosion inhibitor

The current study assessed the anticorrosion features of 6-chloro-2-(4-chlorophenyl)imidazo[1,2-a]pyridine-3-carbaldehyde (AIM) in mitigating corrosion of three different metals: Mild Steel (MS), Copper (Cu) and Aluminum (Al) in 1 M HCl solution. The adsorption process of AIM on these metal surfaces, as well as the stability of the adsorbed layer and its relationship with the type of metal were comprehensively investigated. To achieve our objectives, several techniques were used, such as: Potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), SEM surface characterization, and theoretical approaches. Electrochemical impedance spectroscopy investigations revealed high corrosion inhibition rates, reaching 99.01 %, 96.06 %, and 84.8 % for Cu, MS and Al, respectively, at a concentration of 10−3 M of AIM. Potentiodynamic polarisation validated the mixed type nature of inhibitor, a satisfactory correlation was observed between the results obtained by EIS and those obtained by the PDP technique. The adsorption study showed that the process was mainly controlled by chemical adsorption, and metal dissolution was an endothermic process. Additionally, surface analysis by scanning electron microscopy (SEM) confirmed the formation of a protective AIM film on the electrode surface, resulting in a significant reduction in metal dissolution in the presence of aggressive ions. The exploration of the relationship between molecular structure, inhibitory properties of AIM and the studied metals, was conducted through quantum chemical analysis and dynamic molecular simulation.

Enhancing corrosion resistance of mild steel in acid pickling bath: An investigation of new quinazoline derivatives by synthesis, electrochemical analysis EFM, surface analysis, AFM, DFT and molecular dynamics simulation

The current study examines the ability of two novel heterocyclic Quinazoline derivatives, 2-(4-bromophenyl)-3-phenyl-2,3-dihydroquinazolin-4(1H)-one (DHQ-4-Br) and 2-(4-hydroxy-3-methoxyphenyl)-3-phenyl-2,3-dihydroquinazolin-4(1H)-one (DHQ-3-OMe-4-OH) to adsorb and protect mild steel against corrosion in a molar solution of hydrochloric acid (HCL). The two materials were identified using nuclear magnetic resonance (NMR) spectroscopy and the experimental investigation employed potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), and impedance spectroscopy (EIS). The findings demonstrated that DHQ-4-Br and DHQ-3-OMe-4-OH exhibit increasing inhibitory effectiveness as the concentration of the inhibitors increases. Polarization test results suggest that the two inhibitors exhibited mixed-type behavior. The inhibitory efficiency of DHQ-4-Br and DHQ-3-OMe-4-OH was 94.65 % and 83.94 % respectively. In addition, the Langmuir adsorption model was employed better to understand the adsorption process of the two compounds. The existence of a barrier layer surrounding the SM was demonstrated using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and atomic force microscopy (AFM). The results of the density functional theory (DFT) show that the inhibitors that can take electrons have the strongest interactions with the iron surface.

Study on Oxygen Plasma-Based Copper Etching Process

A plasma-based, room-temperature copper etch process using the chlorine- or bromine-containing feed gas was reported. This simple process could potentially replace the chemical mechanical polishing method in preparing copper interconnects. However, the chlorine- and bromine-containing gases are corrosive and must be handled with expensive equipment following stringent safety procedures. In this paper, the oxygen plasma-based copper etch process is presented. The copper film was converted into a porous and polycrystalline copper oxide film which was subsequently dissolved in a dilute hydrochloric acid solution. The copper film was expanded when converted into an oxide film. The oxidation precursors, i.e., oxygen radicals and ions, were generated in the plasma phase and then transported through the oxide layer to the underneath copper film where the oxidation reaction proceeded. The oxide growth rate is affected by plasma parameters, such as pressure and power, and the kinetics of the oxidation reaction. This new oxygen plasma-based process is a simple solution for preparing copper interconnects for nano and microelectronic products.

ASSESSMENT OF NEWLY SYNTHESIZED SALICYLALDEHYDE-BASED SCHIFF BASES AS CORROSION INHIBITORS FOR CARBON STEEL IN AQUEOUS ENVIRONMENT

A novel and eco-friendly approach for synthesizing two salicylaldehyde-based Schiff bases (2HPP and BHBD) in aqueous environments has been successfully conducted. These synthesized Schiff bases were subjected to a range of physicochemical analyses, including CHNS elemental analyses, molar conductivity measurements, and spectroscopic techniques like IR, electronic, 1HNMR, and mass spectra, to ascertain their properties. The research also involved investigating the inhibitory properties of these Schiff bases against mild steel corrosion in hydrochloric acid solutions at a temperature of 30°C. The results obtained from this study revealed the remarkable inhibitory potential of 2HPP and BHBD on mild steel corrosion in HCl solution. The inhibition efficiency was found to increase with increasing concentration, ultimately reaching an impressive maximum inhibition efficiency of 91.50% and 94.54 % for 2HPP and BHBD, respectively. The adsorption behavior of 2HPP and BHBD followed the Langmuir isotherm, indicating a favorable interaction with the metal surface. Moreover, the investigations included the use of quantum chemical parameters, which were computed utilizing the Density Functional Theory (DFT) method. These calculations included energy gap assessments, which lent support to the excellent inhibiting performance of both Schiff basses. However, BHBD appeared to be a more efficient inhibitor than 2APP.

Optimization of the demineralization process of black soldier fly (Hemertia illucens) pupa shell maggot chitosan and the physicochemical characteristics

Chitosan is a derivative compound of chitin that has undergone deacetylation. Chitosan has three stages of the manufacturing process, including demineralization, deproteinization, and deacetylation. Chitin is also found in the black soldier fly maggot pupae, but maggot pupae contain high minerals content that can affect the purity of the resulting chitosan. Therefore, demineralization treatment is necessary to remove minerals from maggot pupae shells. This study aims to optimize the demineralization process by finding the best type of acid solvent, the best incubation time, and combination treatments. The black soldier fly (BSF) maggot pupa shell was soaked using various formic acid, hydrochloric acid, and nitric acid solutions with incubation times of 60, 120, and 180 minutes. Chitosan characterization was carried out following SNI 7949:2022, including water content, ash content, nitrogen content, pH, deacetylation degree, characterization of functional groups with FT-IR, and as an antimicrobial comparison is formalin. The best demineralization treatment was obtained at 0.5 M nitric acid treatment with an incubation time of 120 minutes. The characterization of chitosan produced 7.81% water content, 0.56% ash content, 4.73% nitrogen content, pH 7.39, and 75.14% deacetylation degree. Characterization of groups on chitosan with FT-IR resulted in the absorption of O-H and N-H groups 3484 cm-1 and 3152 cm-1; C-H 2877 cm-1; and C=O 1653 cm-1. The inhibitory power against E. coli of the BSF maggot pupa shells chitosan is better compared to chitosan standard but not better than formalin.

Bio-inhibitive corrosion effect of carica papaya leaf extract on cold-rolled mild steel in 0.1 M HCl solution

Plant extracts are prone to microbial growth that can lead to microbial-induced corrosion (MIC), a major setback for their performance and stability as corrosion inhibitors. Hence, this work aims to identify the microbes that may cause the ineffectiveness of carica papaya leaf extract (CPLE) as a bio-corrosion inhibitor of cold-rolled mild steel in 0.1 M HCl solution for 48 days at 28℃. Cold-rolled mild steel coupons were immersed in 100 ml of 0.1 M hydrochloric (HCl) acid solution containing 1 g, 2 g, 3 g, 4 g, and 5 g of carica papaya leaf extract (CPLE) for 48 days at 28℃. The gravimetric method was used to determine the coupons' corrosion rate (CR), surface coverage, and inhibition efficiency (IE%) of the CPLE. The functional groups in the CPLE were identified using Fourier Transform Infrared Spectroscopy (FTIR), and the surface appearance of the coupons after immersion was examined using an atomic force microscope (AFM). Gravimetric data showed the coupons dipped in a 0.1 M HCl solution containing 3 g/100 ml of the inhibitor exhibited the highest inhibition efficiency of 87.73%, surface coverage of 0.88, and lowest corrosion rate of 0.00255 mm/day or 0.93 mm/yr, after 48 days at 28℃. In FTIR, transmittance peaks occurred at 1558 cm−1 for amines (-NH) in alkaloid scissoring, 1452 cm−1 for aromatic -C = C in flavonoids, 2932 cm−1 for aliphatic methylene (-CH2) and aldehyde (RCOH) stretching, 1035 and 1077 cm−1 for aromatic-OR in tannin, and 3280 cm−1 for out-of-plane bending of hydroxyl (-OH) in phenolics. Vitamin C (522,940 μg/g), flavonoids (860 μg/g), saponins (637.9 μg/g), terpenoid (48.4 μg/g), phenol (120%μg/g), alkaloid (4.18 μg/g), tannin (59.84%), and glycosides (9.04%) make up the extract's average phytochemical content. AFM presents pits and ridges on the mild steel coupons immersed in 0.1 M HCl solution without the extract. Those immersed in the solutions with varying concentrations of the extract had a passive layer of the CPLE adhering to the surfaces of the coupons thereby preventing the coupon’s direct contact with the acid solution and weight loss. However, over time, microbial growth decreased the efficiency of CPLE due to metabolites. Microbial tests show creamy, irregular and raised bacterial total colony-forming units per gram (Tcfu/g) as 4.6 × 105 Tcfu/g and 1.9 × 107 Tcfu/g in 2 runs. Also, a mixture of white and fluffy appearance and spore formation of fungi population of 4.8 × 105 Tcfu/g and 3.2 × 107 Tcfu/g in 2 Runs made up of Penicillium spp, Coccidioides immitis, Aspergillus flavus, and Fusarium spp, with hyphae, were seen in the solutions containing CPLE.

Comparison of the Reactivity for the Solvent Extraction of Gold(iii) from Concentrated HCl Solutions Among D2EHPA, PC 88A, and Cyanex 272

ABSTRACT In this study, the chemical reactivity of three organophosphorus acidic extractants (D2EHPA, PC 88A, and Cyanex 272) was compared for the extraction of the anionic gold(III) complex, AuCl4 −, from the concentrated hydrochloric acid solutions. The extraction behavior was examined by varying the hydrochloric acid concentration from 1 to 9 M. Among the three extractants, only Cyanex 272 showed significant efficiency in extracting Au(III) with the extraction percentage was proportional to hydrochloric acid concentration. In contrast, the extraction of Au(III) by D2EHPA and PC 88A was not significant. FT-IR spectra analysis indicated that the P=O bond in Cyanex 272 weakened after extraction, suggesting its involvement in the process. Based on the structural differences between the extractants and the observed dependence of gold(III) extraction on the hydrochloric acid concentration, a nucleophilic addition reaction was proposed as the extraction mechanism. Specifically, the phosphoryl oxygen of protonated Cyanex 272 likely forms a coordinate bond with the gold ion in AuCl4 −, facilitating its extraction. This mechanism was supported by both extraction and spectroscopic data, making Cyanex 272 a promising candidate for the selective extraction of Au(III) from highly acidic solutions. The findings offer insights into the extraction of metal ions using organophosphorus extractants in highly acidic environments.

Design, synthesis, and evaluation of a pyrazole-based corrosion inhibitor: a computational and experimental study

By employing a synergistic blend of experimental and theoretical methodologies, we investigated the corrosion inhibition efficacy of a synthesized pyrazole derivative (BM-01) in a solution of hydrochloric acid (1 M). We utilized molecular dynamics (MD) simulations, scanning electron microscopy (SEM), density functional theory (DFT), complexation, plus electrochemical impedance spectroscopy (EIS). We conducted weight loss (WL) measurements from 298 to 328 K. Inhibition efficacy reached a maximum at a BM-01 concentration of 10−3 M, achieving 90.0% (EIS), 90.40% (WL), and 90.38% (potentiodynamic polarization (PDP)). SEM unveiled the shielding of the carbon-steel surface from acid-induced damage by BM-01. The Langmuir adsorption isotherm exhibited a robust fit with a low sum of squares, standard deviation, and a high correlation coefficient. PDP findings indicated that BM-01 acted as a mixed-type inhibitor, predominantly favoring the cathodic process, suggesting potential corrosion-mitigation properties. Theoretical analyses involving DFT, MD simulations, and radial distribution function were conducted to postulate a mechanism and identify an inhibitory layer. Theoretical outcomes aligned closely with experimental data, thereby reinforcing the validity of our findings.

Eliminating the «memory effect» during mass spectrometric determination of mercury

When estimating mercury content by inductively coupled plasma mass spectrometry (ICP-MS), this element adsorbs on the surface of the sample introduction system of the instrument, which creates problems in the determination of trace amounts of mercury. Various methods of cleaning the instrument have been proposed in the literature. Objective: to experimentally compare the effectiveness of trace mercury removal methods proposed in the literature for elemental analysis by ICP-MS and to select the optimal cleaning agent. Methods: Mercury content in solution was determined by the Agilent Technologies 7900 inductively coupled plasma mass spectrometer using 202Hg isotope. Diluted solutions of nitric and hydrochloric acids, solutions of gold chloride, potassium dichromate, thiourea, L-cysteine, potassium bromide, potassium bromate of different concentrations in water and 1% nitric and hydrochloric acids, aqueous solution of ammonium pyrrolidinedithiocarbomate were used as washing agents. Results: The background level of mercury content is achieved by using solutions of copper chloride (5%), thiourea (0.01, 0.1, and 0.5%), L-cysteine (2%), potassium bromide and bromate (0.0005 M) in 1.0% hydrochloric acid solution. The background is lowered by using 3 and 5% HCl, potassium dichromate (60 mg/liter), potassium bromide and bromate (0.01 and 0.05 M) solutions in 1% hydrochloric acid. Application of aqueous solution of ammonium pyrrolidinedithiocarbamate causes sharp degradation of plastic tubes of the sample introduction system. Conclusion: The efficiency of washing agents based on hydrochloric acid is higher than that based on nitric acid and water. The most promising washing agents are bromide-containing solutions and potassium bichromate solution in hydrochloric acid. The optimal way to clean the device is its washing with 0.5 mM potassium bromide solution in 1.0% hydrochloric acid. Its use allows to reduce the background content of mercury and does not complicate the analysis of the content of other elements.

Synergism of Computational Simulation Technique and Machine Learning Algorithm for Prediction of Anticorrosion Properties of Some Antipyrine Derivatives.

This study aimed to predict the selected antipyrine compounds' inhibitory efficiencies and anticorrosion properties in a hydrochloric acid (HCl) environment. Molecular descriptors and input variables were obtained using density functional theory (DFT), and the variance inflation factor (VIF) was employed to reduce redundant variables, leading to the selection of seven quantum chemical descriptors as input variables. Using machine learning techniques such as K-nearest neighbor (KNN) and artificial neural network (ANN), a predictive model was built for 39 antipyrine compounds with known corrosion inhibition efficiencies for carbon and low alloy steel in hydrochloric acid solutions. The models' predictive capability was assessed using cross-validation, with the ANN model showing superior performance, achieving a coefficient of determination (R2) value of 0.715 compared to 0.548 for the KNN model. Performance metrics such as the mean square error (MSE), mean absolute error (MAE), and root-mean-square error (RMSE) further confirmed the superiority of the ANN model over the KNN model. The corrosion inhibition efficiencies (CIEs) of the selected antipyrine compounds ranged from 68.78 to 99.79%, with compound A1 demonstrating the highest CIE of 99.79% and compound A3 the lowest, as evaluated by the ANN model. Analysis of Fukui index parameters obtained from the Mulliken population analysis suggested that the nucleophilic and electrophilic sites play a crucial role in the interactions between the inhibitor and the metal atom through electron donor-acceptor interactions. Moreover, the energy of adsorption (Eads) in kcal·mol-1 decreased in the order of A1 (-187.8) > A2 (-132.0) > A2 (-84.4), with the high negative value of Eads indicating strong and spontaneous adsorption. Further analysis using radial distribution functions and molecular dynamics simulations revealed that inhibitor A1 exhibited predominantly chemisorption, inhibitor A2 showed a mixed type, and inhibitor A3 demonstrated predominantly physisorption, aligning well with the results of the predictive studies.

Effect Of The Composition Of The Etching System MF-HCl (M = Li+, Na+, NH4+) on the gas-sensitive properties of Ti3C2Tх/Tioх nanocomposites

The influence of the nature of MF-HCl etching systems (M = Li+, Na+, NH4+) on the process of synthesis of Ti3C2Tx MXenes on the basis of Ti3AlC2 MAX-phase, microstructure, phase purity, interlayer distance, composition of functional surface groups, thermal behavior and yield of the obtained products has been studied. The room temperature sensing properties of Ti3C2Tx receptor layers deposited by microplotter printing were studied with respect to a wide range of gas analytes (H2, CO, NH3, NO2, NO2, O2, benzene, acetone, methane and ethanol). Increased sensitivity to ammonia was revealed for the MXenes obtained by exposure to hydrochloric acid solutions of sodium and ammonium fluorides and to carbon monoxide for the sample synthesized using the LiF-HCl system. High responses (~20–30% to 100 ppm NO2) were observed for all three receptor materials, but sensor recovery processes were significantly hampered. To improve the sensing characteristics, Ti3C2Tx sensing layers were subjected to relatively low-temperature heat treatment in an air atmosphere to form Ti3C2Tx/TiOx nanocomposites. It was found that a high and selective oxygen response at very low operating temperatures (125-175°C) was observed for the MXenes partially oxidized, which is particularly characteristic of the material produced using the HCl-NaF system.

Thermodynamic Justification for the Effectiveness of the Oxidation—Soda Conversion of Ilmenite Concentrates

This article presents the results of a thermodynamic analysis of the oxidation soda conversion reactions of minerals in ilmenite concentrates in the temperature range of 373–2273 K. The thermodynamic parameters of pseudorutile, pseudobrukite, and the new minerals, zhikinite and spessartine, were calculated for the first time. It has been established that the most important criterion relating to the stability of titanium minerals and related elements, as well as the reaction properties of the structural oxides of metals and silicon, is their degree of oxidation. Oxides of silicon (IV) and manganese have the best reactivity in solid-phase oxidizing alkaline environments (VI). Modeling this process scientifically substantiates the mechanism involved in the destruction of minerals in ilmenite concentrates in the low-temperature region in the presence of atmospheric oxygen and sodium oxide of soda ash, which are decomposed through the absorption of heat and the evaporation of moisture during the dehydration of hydrated minerals of iron and manganese and the dehydration of the soda–ilmenite batch. Tests conducted during pilot metallurgical production at the Institute of Metallurgy and Enrichment (PMP of JSC) confirmed the feasibility of processing high-chromium and siliceous rutile leucoxene ilmenite concentrates, which are unsuitable for traditional pyro- and hydro-metallurgical enrichment methods, through single-stage oxidation soda roasting, followed by the leaching of easily soluble sodium salts of iron and associated impurities with water and a dilute hydrochloric acid solution. The proposed energy-saving method ensures the production of high-purity (>98%) synthetic rutile while eliminating the formation of strong deposits on the lining of roasting units.

Chemical durability of optical temperature sensors made of tellurite glass: Effect of the alumina concentration

Tellurite glass is an amorphous material commonly doped with rare earth ions for the development of optical temperature sensors. Considering the intrinsic properties of glasses, it is expected that these sensors could be used in acidic environments and withstand temperature changes. However, this has not been fully demonstrated since most of the literature is limited to demonstrate the sensor operation under normal conditions. Additionally, there is a lack of information regarding the chemical durability of these glasses and methods to improve it. In this work, a special tellurite glass composition was proposed for the development of optical temperature sensor. The effect of the alumina concentration on the structure, chemical durability and emission properties of the glasses was evaluated. Chemical durability was assessed by monitoring the weight loss of glass samples after immersion in hydrochloric acid solutions at room temperature, vegetable oil or air at 150 °C. The results indicate that the addition of alumina increases the chemical durability of the glass and improves its emission properties. It was found that the average temperature estimated by the optical sensor had a relative error of 1.3 % due to the degradation of the glass caused by remaining immersed in a 1 N HCl solution for 60 days.