Sulfuric Acid Solution Research Articles

Microstructure and corrosion properties of Cr41CoFeNi eutectic high-entropy alloy in sulfuric acid solution

A new eutectic high-entropy alloy (EHEA) of Cr41CoFeNi was prepared by arc melting technique. The microstructure and corrosion resistance of the Cr41CoFeNi EHEA were systematically investigated by EBSD, TEM, EIS and XPS analyses. The results revealed that the Cr41CoFeNi EHEA showed a dual-phase structure consisting of BCC phase and FCC phase, and the morphologies displayed the lamellar eutectic and network-shaped eutectic. Compared with 316 L stainless steel, the Cr41CoFeNi EHEA exhibited a better anti-corrosion property in 0.5 M H2SO4 solution. This was mainly attributed to the formation of a dense and stable Cr-oxide layer on the surface of Cr41CoFeNi EHEA, which retarded further dissolution of the matrix. Moreover, bound water could adsorb metal ions to form a new protective film, which played an important role in improving the corrosion resistance of the Cr41CoFeNi EHEA. However, the elemental segregation and chemical potential difference between phases increased the defects in the passive film and accelerated its pitting corrosion of low potential phase. Moreover, the (Co, Fe, and Ni)-enriched FCC structured phase was preferentially eroded.

Synchronous analysis of acetaminophen, codeine, and caffeine in human fluids employing graphite screen-printed electrodes.

A facile electrochemical approach is proposed for the synchronous determination of acetaminophen (ACP), codeine (COD) and caffeine (CAF) utilizing unmodified screen-printed electrodes (SPEs). The determination of ACP, COD and CAF has been explored across different supporting electrolytes including sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4) and Briton Robinson (B.R) buffer solutions. It was found that a 0.05 mol L-1 sulfuric acid solution is an optimal supporting electrolyte utilized for voltammetric analysis of ACP, COD, and CAF with improved sensitivity, stability, and reproducibility. The electro-analytical sensing of ACP, COD and CAF was investigated using SPEs within linear concentration ranges of 3.0-35.0 μmol L-1, 10-160 μmol L-1 and 10-160 μmol L-1 and revealed competitively low limits of detection (3S/N) of 0.9, 4.8 and 6.3 μmol L-1 for ACP, COD and CAF, respectively. The results indicated the possibility of such a simple and quick electroanalytical protocol for online monitoring of pharmaceutical formulations comprising ACP, COD, and CAF drugs in human fluids with satisfactory recovery.

From bulk banana peels to active materials: Slipping into bioplastic films with high UV-blocking and antioxidant properties

Bananas are among the most produced fruits globally, and their industry generates substantial amounts of peels, which are currently underutilized. Therefore, a simple process was proposed to fully convert banana peel powder (BPP) into bioplastic films using mild pretreatments. The influence of the following variables on film performance was investigated: the type of BPP (unblanched versus blanched), the pretreatment solvent (water – i.e., hydrothermal pretreatment, HTP – or sulfuric acid solution – i.e., dilute acid pretreatment, DAP), and the addition or not of carboxymethyl cellulose (CMC) in the films. The tensile properties of the bioplastics were primarily affected by the presence of CMC, with the films containing 20 wt% of this biopolymer achieving a tensile strength up to 16 MPa. The water vapor permeability was not influenced by any of the studied variables. In contrast, the water contact angle was primarily affected by the pretreatment employed, with all films prepared by HTP displaying a hydrophobic surface. The UV-shielding properties of the materials were mainly influenced by the type of BPP, and all films blocked at least 98% of UV radiation. The antioxidant activity was influenced primarily by the type of BPP, as blanching banana peels helped preserve it. These films are, therefore, promising materials for active food packaging applications, which could contribute to a transition toward a circular bioeconomy.

ВЛИЯНИЕ ХИМИЧЕСКИХ СПОСОБОВ МОДИФИКАЦИИ НА АДСОРБЦИОННЫЕ ХАРАКТЕРИСТИКИ СЛОИСТЫХ СИЛИКАТОВ БЕНТОНИТА

This paper presents the results that allow us to establish the effectiveness of treatments of layered silicates on the example of low-quality alkaline earth bentonite from the Nurlat deposit of the Republic of Tatarstan from the point of view of improving their adsorption properties. The effect of treatments with sulfuric acid solution, sodium carbonate and amorphous silica on the adsorption and structural characteristics of bentonite has been studied. A comparative assessment of the adsorption index for methylene blue bentonites of various deposits is given. The research results showed that the modification of bentonite from the Nurlat deposit with a solution of sulfuric acid and sodium carbonate contributes to the transformation of its adsorption and structural properties, in particular, an increase in the adsorption index and cation exchange capacity by 25 and 40%, respectively. Therefore, modification with sodium carbonate is preferable to activation with sulfuric acid for the studied bentonite deposit, especially given the low cost and concentration of the salt reagent. Under conditions of combining chemical effects on the raw material composition, the increase in adsorption capacity reaches 80%. These transformations of properties are the result of changes in the ion-exchange complex of layered silicates, an increase in the centers of adsorption and their energy. Adsorption-desorption isotherms for nitrogen molecules have been obtained, which are classified as types II and III in accordance with the classification of Brunauer, Emmet and Teller, which indicates a polymolecular adsorption mechanism and a predominantly meso- and macroporous structure of the studied bentonite deposit. It was found that the pore space of bentonite of both basic and modified composition is mainly represented by mesopores with an average diameter of 3,8 nm according to BJH and a volume of 0,057 and 0,068 cm3/g, respectively.

Ti3AlC2 MXene nanosheets as a novel corrosion inhibitor for carbon steel in 0.5 M sulfuric acid solution.

Herein we report that Ti3AlC2 MXene nanosheets were identified as a highly effective cathodic protection corrosion inhibitor for carbon steel in hydrochloric acid solution. Ti3AlC2 Mxene nanosheets form a stable inhibition layer on metal surfaces due to their high adsorption capacity and act as a barrier or protective film to prevent attacks from corrosive substances and thus lead to an extended metal service life.

The role of solution temperature in characteristics of TiO2 nanotube arrays prepared on Ti foil in acid solution.

The characteristics of TiO2 nanotube arrays (TNTs) prepared on Ti foil in sulfuric acid solution that contains Cl- under different temperatures are investigated by field emission scanning electron microscopy (FESEM), electrochemical impedance spectroscopy (EIS), Mott-Schottky measurement and Raman spectra. The solution temperature significantly affects the morphologies of TNTs, i.e., when solution temperature rises from -10 °C to 90 °C, the inner diameter of the nanotube increases and the barrier layer thickness decreases, and, as TNTs display n-type semiconductive properties, the donor density (ND) and corrosion protection decrease. Two types (types I and II) of pulse temperature are used to fabricate TNTs, in which type I is firstly anodized at a low temperature for time t, and then increases to a high temperature. While for type II, the solution temperature order is opposite to that of type I. The ND of TNTs in the case of type I is lower than ND of TNTs in the case of type II. ND decreases with the increased pulse step time for type I, while ND increases with the increased pulse step time for type II.

Study on the behavior of impurity removal from lithium-iron-phosphate slag using the ultrasonic-assisted sulphuric acid leaching

The recovery of iron phosphate from the leaching slag of used lithium iron phosphate cathode materials is a crucial step to achieve closed-loop recovery of lithium iron phosphate, which has not yet been effectively accomplished. In the study, ultrasonic-assisted sulfuric acid leaching was used to remove impurities in the iron phosphate, to meet the stringent impurity content requirements for battery-grade iron phosphate regarding impurity content. Optimization of leaching conditions involved a sulfuric acid concentration of 0.2 mol?L-1, acid-leaching time of 30 min, power of 50 W, and reaction temperature of 80?. Under these conditions, the removal efficiencies of Cr, Cu, Ni, and Zn in iron phosphate were 26.09%, 83.0%, 75.9%, and 96.3%, respectively. Simultaneously, the content of impurity elements Cr and Zn concurred with the standard for battery-grade iron phosphate (HG/T 4701-2021), with both 50 ppm and 10 ppm contents. The leaching results indicated the effectiveness of ultrasound in enhancing the removal of impurity elements in iron phosphate within a sulfuric acid solution. Further analyses, including XRD, particle size, TEM, and XPS indicated that the surface of the iron phosphate particles cavitated after ultrasonic acid leaching, resulting in the formation of numerous pores. Additionally, particle collisions led to a reduction in particle size, with no generation of by-products during the process. This innovative approach not only contributed to the removal of impurity elements but also provided insights into the reuse of leaching slag (iron phosphate) and offered guidance for the recovery of metals from waste lithium iron phosphate cathode materials.

Pitting Corrosion of Titanium Depending on the Properties of the Passive Film

Pitting corrosion behavior of Ti with passive film under breakdown was investigated from the points of film thickness and oxygen-related species in the film. A Ti specimen was passivated in a sulfuric acid solution at 5.0 VAg/AgCl at 323 and 353 K. A passivation current decreased, increased and then slightly decreased with increasing a passivation time, the periods were denoted as Region (i), (ii) and (iii), respectively. A pitting potential of the specimen passivated in Region (i) was almost independent of, and that in Regions (ii) and (iii) shifted higher with increasing the time. Change in an amount of water desorbed from the film with the time was similar to that in the pitting potential. It was found from XPS test that change in a film thickness with the passivation time was also similar to that in the pitting potential. Furthermore, the desorbed water was derived from hydroxide or both of hydroxide and bound water in the film. The findings indicate that the film passivated in Regions (ii) and (iii) was under breakdown, and suppression of the pitting corrosion is caused by increasing both of the film thickness and the amount of hydroxide and bound water in the film.

Recovery of pure lithium phosphate from sulfuric acid leaching solutions of spent LiFePO4 batteries by solvent extraction and chemical precipitation

With the increasing use of electric vehicles, the demand for lithium iron phosphate batteries (LiFePO4) has risen sharply. Therefore, the recycling of metals from these batteries at the end of their life is necessary. In this study, a hydrometallurgical process for the recovery of lithium phosphate from spent LiFePO4 batteries was developed. The effects of the parameters on the recovery process, consisting of leaching, solvent extraction, and precipitation were investigated. The addition of H2O2 to the H2SO4 solution was ineffective for the selective leaching of Li(I) over iron. The results showed that Li(I) and iron were completely dissolved by 1.5 mol/L H2SO4, 100 g/L pulp density at 25 ?C for 60 min at 300 rpm. After oxidation of Fe(II) in the leaching solution by addition of H2O2, Fe(III) was completely separated from the solution by five steps of cross-flow extraction with 1.0 mol/L D2EHPA at room temperature. The loaded Fe(III) was successfully separated by four steps of cross-current stripping with 50% (v/v) aqua regia solution. Finally, most Li(I) was recovered by precipitation of lithium phosphate from the iron-free raffinate by maintaining the pH of the solution at 11 and the temperature at 95 ?C for 30 min. The optimum conditions for the complete dissolution of LiFePO4 batteries by sulfuric acid solution and for the separation of iron and lithium ions from the leaching solutions were determined. A hydrometallurgical process was proposed for the recovery of pure lithium phosphate from spent LiFePO4 batteries.

Recovery of Scandium, Nickel and Cobalt from Hydrometallurgical Waste of Laterite

Recovery of new-energy critical metals including scandium, nickel and cobalt as well as copper and zinc from a neutralization residue produced in laterite hydrometallurgical process has been studied. Effect of leaching parameters such as acid consumption, solution pH and temperature has been investigated. It was found that scandium, nickel, cobalt and copper could be recovered at high efficiencies from the residues by selective leaching using sulphuric acid solutions under ambient conditions, while the co-leaching of impurities including iron, aluminium and silicon was low under the optimal conditions. The nickel, cobalt, copper and zinc in the leaching solution could be further concentrated into mixed sulphides and separated from impurities by sulphide precipitation.

Nano-protrusions in intercalated graphite: understanding the structural and electronic effects through DFT.

Complex phenomena characterize the intercalation of ions inside stratified crystals. Their comprehension is crucial in view of exploiting the intercalation mechanism to change the transport properties of the crystal or obtaining a fine control of crystal delamination. In particular, the relationship between the concentration and nature of intercalated ions and surface structural modifications of the host stratified crystal is still under debate. Here, we discuss a theoretical effort to provide a rationale for some structural changes observed on the highly oriented pyrolytic graphite (HOPG) surface after electrochemical treatment in perchloric and sulphuric acid solutions. The formation of the so-called nano-protrusions on the basal plane of intercalated graphite was previously observed with scanning tunneling microscopy (STM). In this work, we employed both STM and density functional theory (DFT) simulations to elucidate the physical and chemical mechanisms driving the emergence of these nano-protrusions. The DFT results show that, in a bilayer graphene system, the presence of a single ion can generate a nano-protrusion with 2.49 Å height and 21.27 Å width. In the deformed area, the C-C bond length is stretched by about 2.5% more than the normal graphene bond. These values are of the same dimensional scale as those reported in previous STM experimental results.25 However, the simulated STM images obtained by increasing the amount of intercalated ions per area suggest that the presence of more than one ion is needed for the deformation of the uppermost graphite layer during the early stages of intercalation. In contrast, in a multilayer graphene system, no significant surface deformation is detected when ions are intercalated between the third and fourth layers. Charge analysis indicates an altered distribution of the charges as a consequence of the intercalation. The charge transfer from graphene layers to the intercalated ions results in a surface layer more prone to oxidation.

Molecular simulation of competing sorption of U(VI) on the surface of clay and mineral wastes

In-situ uranium extraction technology, nuclear fuel processing, water purification require detailed study of sorption process of U(VI) and some compete coxisting ions onto clay and waste materials. The Monte-Carlo method used for modeling of the U(VI), Al(III), Fe(II)/Fe(III) sorption on the surface of the clay materials (vermiculite, kaolinite, illite, palygorskite, biotite, montmorillonite, nontronite) and mineral wastes (zincite, franklinite) which are capable to effective sorption of U(VI) on the mineral surfaces. The molecular modeling used different species (UO22+, UO2SO4, UO2(SO4)22−, AlSO4+, Al(SO4)2−, FeSO4−) in acidic sulfate solutions (Н2SO4, НSO4−, SO42−). Different sorption energy values indicate chemical nature of the adsorption process with predominant sorption of uranium ions (UO22+ and UO2(SO4)22−) compared with Fe/Al ion species.

Structure and dynamics of aqueous VOSO4 solutions in conventional flow through cell design: a molecular dynamics simulation study.

A theoretical model has been proposed to study the structure and dynamics of aqueous vanadyl sulfate (VOSO4) solution used in the conventional flow (CF) through cell design operating under varying thermodynamic conditions. Classical molecular dynamics simulations have been carried out for aqueous solutions of vanadyl sulfate (VOSO4) and sulfuric acid (H2SO4) at two different concentrations and temperatures considering the temperature dependent degree of dissociation of sulfuric acid. The MD trajectories are used to study the equilibrium structural, dynamical properties such as viscosity, diffusivity and surface tension of the aqueous solution of vanadyl sulfate (VOSO4). According to the new model, the cation-cation and cation-anion interaction should be low in order to have a good current density in the conventional flow through cell design and further explains the importance of considering mass transport when designing high energy density redox flow batteries. The model is further validated by calculating the viscosity of each system, individual diffusion coefficient of each ion and by comparing them with the experimental data wherever they are available.

Behavior of boron contained in foil brazing filler metal and corrosion resistance in dilute sulfuric acid and sodium chloride aqueous solutions

Behavior of boron contained in foil brazing filler metal and corrosion resistance in dilute sulfuric acid and sodium chloride aqueous solutions

Regenerated Silica Gel for Isolation of Ethyl p-Methoxycinnamate from Kaempferia galanga rhizome

The main component from Kaempferia galanga rhizome extract is known as ethyl p-methoxycinnamate. Column chromatography using silica gel is one of the commonly used method for obtaining high purity of ethyl p-methoxycinnamate from K. galanga rhizome extract. In this study, the regeneration of silica gel then utilized for checking its reusability to undergo the isolation of ethyl p-methoxycinnamate. The silica gel was regenerated by utilizing two methods: (a) the direct furnace at 600 ⁰C; (b) the stirring process with aqueous solution of sulfuric acid which followed by furnace at 600 ⁰C. K. galanga rhizome extract was obtained under maceration by hexane. Regenerated silica gel was characterized by XRF and FTIR. The ethyl p-methoxycinnamate content was determined by UV-Vis spectrophotometry. The regenerated silica gel showed almost similar characteristic with the original commercial silica gel. The K. galanga rhizome extract after underwent column chromatography with regenerated silica gel showed high stability. This result ensured the utilization of regenerated silica gel can be considered for isolation of ethyl p-methoxycinnamate from K. galanga rhizome extract.

One-pot spray pyrolysis method for nanostructured cobalt sulfide–C composite microspheres using recovered cobalt sulfuric acid solution and their excellent properties as anode materials for potassium-ion batteries

A pioneering synthesis approach for nanostructured cobalt sulfide-C composites from waste materials is proposed. By combining recycling processes with one-pot spray pyrolysis, a cost-effective and efficient synthesis method is achieved.

Vertical temperature gradient of the ocean as perspective source of renewable energy

In our research we studied the efficiency of converting low-grade heat into electrical energy. The studied cycle is based on sulphuric acid solutions separation in temperature gradient and further electricity generation in concentration galvanic cell. In our calculations we used combined method. To calculate obtained electrical energy we used experimental date, because it is rather difficult to predict electrodes overpotential. The heat, consumed in distilling process, was calculated in theory. As the result of calculations it was shown that if temperature difference is 20 K (T1=300K and T2=280 K) the efficiency of the cycle is about 1.5 percent (about 23% of Carnot cycle efficiency). Such temperature difference could be provided, for example, by vertical thermal gradient of the ocean.

CFD modelling of the air preheater fired with gas mixture to find the cause of the preheater damage

Since various fuels, such as natural gas, blast furnace gas, coke oven gas, and a mixture of the three, are burned in the boiler, there is a danger of corrosion caused by sulphuric acid. Sulphur dioxide produced after combustion and condensed water vapour from flue gases on cold tube surfaces form sulphuric acid. Sulphuric acid solution flowing down the vertical tubes of the air heater causes corrosion not only of the air heater tubes but also of the horizontal water heater tubes located below. A simulation of the flow and heat exchange on the flue gas and air sides was performed to determine the areas of the air heater where the temperature of the air heater tubes is low and condensation may occur. Based on the measured air and flue gas mass flows, the measured flue gas temperatures behind the heater, and the air temperature at its inlet, the flue gas temperature before the air heater was determined using the ε-NTU (Effectiveness-Number of Transfer Units) method. Based on CFD modelling and experimental research, the areas in the heater where sulphuric acid can form at given outside air temperatures were determined.

Kinetic of Dissolution of Nickel Limonite Calcine by Sulfuric Acid Solution

Currently, more than 60% of nickel processing is carried out using nickel sulfide as a raw material. Nonetheless, due to the depletion reserves of nickel sulphide, nickel laterite has drawn a lot of interest to be processed as raw material. Nickel laterite in Indonesia is generally found in low grades, with nickel concentration of <1.15%. One method of treating nickel limonite is leaching in a sulfuric acid solution. This study aims to determine the reaction rate in the leaching process of calcine nickel limonite and the effect of sulfuric acid concentration and leaching temperature on the percent nickel extraction. In this research, the limonite ore from Pomalaa, Southeast Sulawesi, Indonesia, which has undergone a reduction process, was used as raw material. This research was conducted by leaching method on nickel limonite calcine using sulfuric acid reagent with 0.2, 0.5, and 1 M concentration variation, temperature variations of 60, 70, and 90°C, stirring speed 500 rpm, and %S/L (w/w) 10%. In this leaching research, the activation energy obtained at a sulfuric acid concentration of 0.2, 0.5, and 1 M are 13,7379 kJ/mol, 19,7582 kJ/mol, 20,3161 kJ/mol, respectively. The leaching process of nickel limonite calcine was controlled by diffusion. The optimum nickel extraction percentage in this study was 97.45%, obtained at a concentration of 1 M sulfuric acid, temperature of 70 °C, and leaching time of 240 minutes.

Synergistic inhibitive effect of a hybrid zinc oxide-benzalkonium chloride composite on the corrosion of carbon steel in a sulfuric acidic solution

Abstract Zinc oxide and quaternary ammonium-type surfactants have been separately recognized for their anti-corrosive efficiencies. Their composite, not investigated so far, could provide a synergetic anti-corrosion effect. In this respect, the aim of this study is to synthesize a composite material consisting of zinc oxide and benzalkonium chloride (ZnO-BAC) in varying mass ratios (3:1, 1:1, and 1:3). The inhibitory properties of the ZnO-BAC composite against carbon steel corrosion in a 0.5 M sulfuric acid solution were assessed under ambient conditions. First, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to examine the chemical structure of the prepared composite. Then, the corrosion inhibitive performance of the devised inhibitors was screened using electrochemical, hydrogen collection, and weight loss measurements. Further, the surface morphology was examined using a scanning electron microscope, both before and after immersion in the corrosion medium. The electrochemical measurements indicate that the prepared inhibitor exhibits a predominant cathodic inhibition behavior and the maximum inhibition efficiency, approximately 91.9%, was achieved for one-to-one mass ratio. Similar results were obtained from weight loss and hydrogen evolution measurements, which showed that the ZnO-BAC composite reduced the corrosion rate of carbon steel by 69.9% and 64.9%, respectively. Finally, molecular dynamics and an adsorption equilibrium model were used to elucidate the mechanism of corrosion inhibition by the ZnO-BAC composite, which exhibits a high adsorption energy on the iron surface.