Gravimetric Experiments Research Articles

Adsorption, corrosion inhibition mechanism, and computational studies of Azadirachta indica extract for protecting mild steel: Sustainable and green approach

The extract of Azadirachta indica (AI) leaves has been explored as a green inhibitor for mild steel (MS) in 5.0 m hydrochloric acid by computational (DFT, Langmuir/Freundlich adsorption, frontier molecular orbital, and molecular dynamics simulation) and experimental (polarization, gravimetric, gasometric, and impedance) techniques. Corroded surfaces have been investigated by metallurgical microscopy and SEM techniques. The impedance parameters and inhibition efficiency were found to increase with AI extract concentration, the latter from 50.64% to 89.25%. Various theoretical parameters, such as electronic charge in the HOMO/LUMO, Fukui function, metal−inhibitor interaction energy (−22.12 kJ/mol), adsorption energy (7.86 kJ/mol), back-donation energy, chemical potential (3.95 eV), and global hardness (1.75 eV), imply high adsorption of AI extract (flavonoid as major constituent) on MS. SEM and metallurgical imaging techniques have proved the growth of a uniform barrier film on the surface of MS with increasing AI extract concentration. The numbers and intensities of pits and cracks decrease with increasing AI extract concentration. A maximum of 89.25% inhibitory efficiency was shown by AI. Wastewater from gravimetric experiments was examined for biocompatibility and biodegradability, and was found within the permissible range.

Water sorption and transport in Silurian shales

We have studied the transport of water in shales through gravimetric water vapour sorption experiments. Kinetic data have been evaluated and several kinetic models have been compared, with emphasis on time-dependent diffusivity models. The effective diffusivities as a function of relative pressure show an initial increase corresponding to the sorption to primary adsorption centres, followed by water cluster formation. The final decrease in effective diffusivity is connected with flattening of the pore-mouth meniscus. Introducing the flow rate kinetic parameter enables samples with different amounts of adsorbed water to be compared, showing that the highest value of the flow rate kinetic parameter is connected with the sample with largest surface area and the greatest micropore volume.

Innovative characterization of original green vanillin-derived Schiff bases as corrosion inhibitors by a synergic approach based on electrochemistry, microstructure, and computational analyses

Three vanillin derivatives (VTRIS, VTOS, and VCNG) were synthesized using the principles of Green Chemistry and evaluated as corrosion inhibitors for mild steel in acid media. Their anticorrosive efficiencies were obtained via gravimetric and electrochemical experiments, reaching an average maximum of 82.2%, 83.1%, and 93.1% efficiency for VTRIS, VTOS, and VCNG, respectively. Microstructure analysis alongside Atomic Force Microscopy images was used to rationalize the behavior of the polarization curves and verify the preferred adsorption sites of the organic molecules on the metallic surface. AFM and SEM confirmed the formation of a protective layer. Crossing data between gravimetric and electrochemical measurements showed the difference amid mono- and multi-layer adsorption inhibitors. Ab initio calculations were in excellent agreement with experimental results, unveiling the importance of the choice of the correct Electron Work Function for the calculation of the transferred electrons (ΔN). Such results are of fundamental importance to open the corrosion field for advanced analysis about reliable computed electrochemical parameters and crosslinked measurements able to understand the adsorption process of the inhibitors. Only the synergy among experimental and computed data made this possible.

Study of Anticorrosive Action and Synthesis of 2-(Phenoxymethyl)-5-p-tolyl- 1,3,4-oxadiazole in 1 M Hydrochloric Acid Medium for Mild Steel

Oxadiazole derivative 2-(phenoxymethyl)-5-p-tolyl-1,3,4-oxadiazole (2POM5PTO) was prepared by condensation of phenoxymethyl hydrazine with p-tolualdehyde. Further tested as corrosion inhibitor for mild steel via electrochemical methods, potentiodynamic polarization (PDP) and gravimetric experiments. An increasing trend in inhibition efficiency has been seen on raising the concentration of 2POM5PTO. PDP technique reveals the mixed-type inhibitor behaviour of 2POM5PTO. The depressed semicircular Nyquist plot explains that the charge transfer resistance increased with inhibitor concentration while double-layer capacitance (Cdl) decreased. The surface elucidation was done by scanning electron microscopy. The studied inhibitor obeys the Langmuir adsorption isotherm.

Fluoride vaporization and crystallization of CaF2–CaO–Al2O3–(La2O3) slag for vacuum electroslag remelting

The vaporization and crystallization of CaF2–CaO–Al2O3 slags with different La2O3 contents for electroslag remelting were investigated by various analytical methods. The results show that the main volatiles from investigated slag within 7.4 wt% La2O3 content at 1723 K are CaF2 and AlF3. The weight loss of CaF2–CaO–Al2O3-(La2O3) slags decrease with increase of La2O3 content in both thermo gravimetric experiment and vacuum condition. The addition of La2O3 within 7.4 wt% reduces the viscosity and breaking temperature of investigated slag, and the change of viscosity is not the main reason to inhibit the fluoride vaporization. The vapor pressure of CaF2 and AlF3 at 1723 K decreases with increase of La2O3 content because of the changes in component activity. Thus, fluoride vaporization becomes weakened. The crystalline phases of CaF2–CaO–Al2O3 slag are 11CaO·7Al2O3·CaF2 and CaF2, while the crystalline phases of slag within 7.4 wt% La2O3 content are (CaLa)Al3O7, La(AlO3) and CaF2. The La2O3 addition can decrease the crystallization temperature of CaF2 and prevent the precipitation of 11CaO·7Al2O3·CaF2.

Corrosion inhibition and adsorption studies of Ammonium oxalate for mild steel by computational and experimental techniques: A sustainable approach

• AO was tested as corrosion inhibitor for mild steel in 0.5 M HCl. • Gravimetric, polarization, impedance, metallurgical, DFT, LAI methods were used. • AO was proved to be very good anti-cracking and anti-pitting agent. • AO shows 94.94% corrosion inhibition efficiency for mild steel. • BOD and COD of wastewater was found to be within the permissible limits. The exact mechanism of inhibition and adsorption is very essential for designing acid corrosion inhibitors. So far sincere efforts are lacking in explaining the exact mechanism of adsorption and corrosion inhibition for acid corrosion inhibitors. Ammonium oxalate (AO) was investigated as a highly efficient corrosion inhibitor for mild steel in 0.5 M HCl by different theoretical and experimental methods. Experimental methods like gravimetric, impedance, polarization, and metallurgical microscopy were supported by theoretical techniques like DFT, MD simulation, Frontier molecular orbital, and adsorption isotherm studies. Surface studies like the morphology of corroded specimens, nature, and type of corrosion were carried out by metallurgical microscopy technique. Different chemical interaction parameters (global reactivity parameters) between the inhibitor and mild steel provide sufficient information about the adsorption and inhibition mechanism shown by AO for mild steel. A linear correlation regression coefficient was observed between AO concentration and inhibition efficiency. A maximum of 94.94% inhibition efficiency was observed at a 1000 ppm concentration of AO. The polarization study shows that AO act as a mixed inhibitor. Impedance study proves that an increase in AO concentration leads to an increase in charge transfer resistance and hence barrier film thickness. The length of pores, percentage porosity, and intensity of cracks decreases appreciably after the addition of 100 ppm of AO. The biochemical assay of waste acid after gravimetric experiments was observed to be within permissible limits. Ammonium oxalate (AO) was investigated as a highly efficient corrosion inhibitor for mild steel in 0.5 M HCl by different theoretical and experimental methods. Experimental methods like gravimetric, impedance, polarization, and metallurgical microscopy were supported by theoretical techniques like DFT, MD simulation, Frontier molecular orbital, and adsorption isotherm studies. Surface studies like the morphology of corroded specimens, nature, and type of corrosion were carried out by metallurgical microscopy technique. Different chemical interaction parameters (global reactivity parameters) between the inhibitor and mild steel provide sufficient information about the adsorption and inhibition mechanism shown by AO for mild steel. A linear correlation regression coefficient was observed between AO concentration and inhibition efficiency. A maximum of 94.94% inhibition efficiency was observed at a 1000 ppm concentration of AO. The polarization study shows that AO act as a mixed inhibitor. Impedance study proves that an increase in AO concentration leads to an increase in charge transfer resistance and hence barrier film thickness. The length of pores, percentage porosity, and intensity of cracks decreases appreciably after the addition of 100 ppm of AO. The biochemical assay of waste acid after gravimetric experiments was observed to be within permissible limits.

Water sorption by ionic liquids: Evidence of a diffusion-controlled sorption process derived from the case study of [BMIm][OAc

The hydrophilicity of ionic liquids (ILs) could be exploited as desiccants or in sorption-driven heat transformation, yet reports of water sorption isotherms of pure ionic liquids are still scarce. Here, water sorption studies for the six pure hydrophilic ionic liquids with 1-ethyl-3-methylimidazolium [EMIm]+ or 1-butyl-3-methylimidazolium [BMIm]+ cations and acetate [OAc]−, formate [HCOO]− or lactate [Lac]− anions show a steady and high water uptake with a small hysteresis between absorption and desorption over the relative pressure range of p/p0 = 0–0.9 for the first time. Repeated static volumetric sorption measurements with different amounts or different surface area of the example IL [BMIm][OAc] reveal a slow and strongly diffusion-driven sorption process stemming from the absorption of surface-adsorbed water into the bulk IL. Extrapolation of the water uptake to very small IL amounts with negligible kinetic hindrance gives an equilibrium water uptake capacity of over 2100 mg/g(IL) at p/p0 = 0.9. Gravimetric control experiments at a relative humidity of 75.5% confirm the time-dependence with the IL surface area at the gas–liquid-interface and the amount of the IL to reach the equilibrium uptake of 1040 mg/g at p/p0 = 0.75.

The effects of water purity on removal of hydrophobic substances from solid surfaces without surfactants

HypothesisDetergents used in everyday life for cleaning and washing are a source of water pollution and can have a negative effect on human health and the environment. To reduce their negative impact, a new trend of using only purified water for washing and cleaning applications is emerging. A scientific basis of this method needs to be established, as its mechanisms and the efficiency should be better understood. ExperimentsIn this work, we investigate the effect of water purity on the removal of hydrophobic films from solid surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and gravimetric experiments. We compared the cleaning efficiency of TAP water, two grades of purified water, NaCl solution and SDS solution. FindingsThe QCM-D results show that both grades of purified water remove more than 90% of Vaseline deposited of the surface while tap water only 75%. SDS solution fully removes the deposited layer. Gravimetric experiments with removal of olive oil from hydrophilic and hydrophobic surfaces also indicate higher efficiency of purified water grades. Contact angle experiments show that pure water facilitates roll-up mechanism of cleaning. We suggest that due to lower ionic strength, purified water increases electrostatic repulsion and promotes the cleaning process.

On the BET Surface Area of Nanocellulose Determined Using Volumetric, Gravimetric and Chromatographic Adsorption Methods

Volumetric N2 adsorption at −196°C is generally accepted as “gold standard” for estimating the Brunauer-Emmet-Teller (BET) surface area of nanocellulose. It is unclear however, whether the BET surface area of nanocellulose obtained at such low temperatures and pressures is meaningful at an absolute sense, as nanocellulose is used at ambient temperature and pressure. In this work, a systematic evaluation of the BET surface area of nanocellulose using highly crystalline bacterial cellulose (BC) as model nanocellulose was undertaken to achieve a comprehensive understanding of the limitations of BET method for nanocellulose. BET surface area obtained using volumetric N2 adsorption at −196°C was compared with the BET surface area acquired from gravimetric experiments based on n-octane adsorption using dynamic vapour sorption (DVS) and n-octane adsorption determined by inverse gas chromatography (iGC), both at 25°C. It was found that the BET surface area calculated from volumetric N2 adsorption data was 25% lower than that of n-octane adsorption at 25°C obtained using DVS and iGC adsorption methods. These results supported the hypothesis that the BET surface area of nanocellulose is both a molecular scale (N2vs n-octane, molecular cross section of 0.162 nm2vs 0.646 nm2) and temperature (−196°C vs 25°C) dependent property. This study also demonstrates the importance of selecting appropriate BET pressure range based on established criteria and would suggest that room temperature measurement is more relevant for many nanocellulose applications.

Evaluation of impact of surface diffusion on methane recovery via carbon dioxide injection in shale reservoirs

Injection of carbon dioxide into shale reservoirs is a promising technology for enhancing natural gas recovery and reducing greenhouse gas emissions. Nanoscale phenomena contribute to a significant difference in mass transfer processes within shale-gas reservoirs compared to conventional gas reservoirs. Previous investigations have shown the significance of surface diffusion to gas transfer mechanisms. Surface diffusion was added to an established apparent permeability model, which was then applied for the first time to numerical reservoir simulations to model CO2 injection techniques. Most publications to date have used a theoretical model to predict surface diffusion coefficient in a low-pressure condition, whereas, in this paper, it has been estimated from gravimetric experiments. Shale reservoirs, with different reservoir and petrophysical properties, were generated to investigate the efficiency of transport of CO2 via surface diffusion. A recently proposed fractal model for surface diffusion was used to investigate the impact of rock surface roughness on CH4 production. The results show that surface diffusion plays a significant role in increasing CH4 recovery by up to 3.2% when the average pore radius is less than 2 nm. In particular, a high surface fractal dimension can potentially enhance CH4 production by up to 1.5% and should not be neglected when the average pore radius is less than 1 nm. In areas with high surface capacity, adsorption of CO2 and desorption of CH4 molecules may increase by up to 2.74% and 2.3%, respectively, when compared to models with no surface diffusion. In all the reservoirs examined, geostatistical reservoir simulations showed that reservoir heterogeneity is not favourable to methane recovery via CO2 injection techniques, except for the Barnett shale reservoir. To the best of our knowledge, this work is the first to implement an apparent model within a reservoir simulator to investigate the impact of surface diffusion on methane recovery via CO2 injection techniques at various shale reservoirs with different properties.

Anticorrosion and dispersive adsorption studies of natural andrographolide on carbon steel in acid-chloride environments

Andrographolide, a bioactive naturally occurring labdane diterpenoid with outstanding antioxidant effects in medicine, has been isolated and purified from Andrographis paniculata, and applied in acid-chloride environments for the corrosion protection of carbon steel. Upon isolation, the phytochemical was identified by NMR and FTIR, while its corrosion inhibition evaluation was achieved by combined electrochemical and gravimetric experiments. The adsorption of andrographolide on carbon steel was examined by SEM, FTIR, and 3D surface measurement, and computational studies were used to describe the adsorption characteristics and properties. The experimental measurements revealed that andrographolide is an effective mixed-type corrosion inhibitor whose efficiency was dependent on both its concentration and the temperature of the environment, with maximum inhibition efficiency of 92.4% recorded for 2.0 g/L andrographolide after 48 h at 318 K. The adsorption of andrographolide and its anticorrosion capacity on carbon steel surface was confirmed by the employed surface analytical techniques, while molecular electrostatic potential, conceptual density functional theory, and molecular dynamics simulation predicted the quantum chemical details and binding properties of the phytochemical on Fe (110) surface at different temperatures.

Chemical vapor transport for intercalation reactions: Synthesis of a 1st stage DyCl3 graphite intercalation compound

In this work, we present a chemical vapor transport process involving the gaseous species DyAl3Cl12(g) in order to perform the intercalation of dysprosium trichloride into graphite. Even if it is known that such a reaction must be performed under chlorine atmosphere, this work reveals that an increase of the Cl2 pressure in the synthesis reactor improves the intercalation yield. By combination of gravimetric measurement, EDX analysis and 00l X-ray diffraction experiments, we evidence the synthesis of a novel 1st stage DyCl3-Graphite Intercalation Compound (GIC). The sample obtained in this study is a mixture of 1st stage DyCl3-GIC and 2nd stage AlCl3-GIC. However, considering the 1st stage DyCl3-GIC, the data collected in this work are in agreement with a IC repeat distance of 982 pm and a C8.1DyCl3.9 formula. Along the c-axis, the intercalated sheet is three-layered and exhibits a Cl-Dy-Cl stacking sequence existing in pristine chloride.

Kinetics of oxidation roasting of molybdenite with different particle sizes

The kinetics of oxidation roasting of molybdenum concentrate was studied by differential thermal− gravimetric experiments and non-isothermal analysis methods. The results show that high temperature is beneficial for oxidation of molybdenum concentrate. The initial oxidation temperature of the molybdenum concentrate is 450 °C, and the rapid oxidation occurs above 500 °C. The oxidation process conforms to the unreacted shrinking nucleus model. The early stage of the oxidation is controlled by chemical reaction with the apparent activation energy of 123.180 kJ/mol, while the later stage is controlled by internal diffusion with the apparent activation energy of 80.175 kJ/mol. Moreover, the oxidation rate is closely related to particle size of the concentrate. The smaller the particle size is, the larger the oxidation rate is.

Carbon steel corrosion inhibition in acid medium by imidazole-based molecules: Experimental and molecular modelling approaches

This paper deals with application of imidazole (IMI) and four imidazole derivative molecules: 4-(imidazole-1-il)-phenol (PHEN), [4-(1H-imidazole-1-yl)-phenyl]methanol (METH), 2-(1H-imidazol-1-yl)-1-phenylethan-1-one (ETHAN) and 4-(1H-imidazole-1-yl)benzaldehyde (BENZ), towards corrosion inhibition of 1020 carbon steel in acidic medium. From IMI to ETHAN, the corrosion inhibition efficiency more than doubled in gravimetric experiments and increased 85% and 68% in the potentiodynamic polarization and electrochemical impedance assays, respectively. Both gravimetric and electrochemical tests gave the following decreasing order for the corrosion inhibition efficiency: BENZ > ETHAN > METH > PHEN > IMI. Quantum chemical calculations based on density functional theory (DFT) method showed that global hardness of the inhibitor molecules and inhibition efficiency were inversely proportional, which means that a softer molecule (or lower charge/radius ratio considering HSAB theory) leads to higher anticorrosion efficiency. Monte Carlo method (MC) was used to calculate the adsorption energies in a simulated water environment, and Compass force field was selected towards obtaining the solvation energy between inhibitor and metallic surface. The calculated solvation energy showed an inverse correlation between solvation energy and corrosion inhibition, having BENZ molecule lower solvation energy and lower global hardness which explains better anticorrosion efficiency among other IMI-based molecules, which shows the importance of molecule polarity over the corrosion inhibition of carbon steel.

Study on corrosion behavior of new corrosion inhibitor imidazole derivatives for mild steel in oil‐in‐water emulsion

Two imidazole derivatives, 2‐(2‐((benzo[d]thiazol‐2‐ylthio)methyl)‐4,5‐dihydro‐1H‐imidazol‐1‐yl)ethan‐1‐ol (BTM) and 2‐(2‐((1H‐benzo[d][1,2,3]triazol‐1‐yl)methyl)‐4,5‐dihydro‐1H‐imidazol‐1‐yl)ethan‐1‐ol (BTMS), as a new corrosion inhibitor were synthesized, and their inhibition behaviors for mild steel contained in emulsion were investigated by gravimetric experiment, electrochemical tests, and theoretical calculations. The results show that the inhibition effect of BTMS is better than that of BTM, the maximum value of the inhibition efficiency reaches 97.9%. The resultant adsorption films from BTM/BTMS adsorbed on mild steel, effectively inhibiting the corrosion of mild steel is mainly through chemisorption and follow to Langmuir's adsorption isotherm.

Investigation of Drying Curves of Lithium‐Ion Battery Electrodes with a New Gravimetrical Double‐Side Batch Dryer Concept Including Setup Characterization and Model Simulations

Herein, an experimental setup comprised of a stationary convection dryer (Comb Nozzle Dryer) supplemented by a measurement for gravimetric drying curves is introduced. The drying process of anodes for lithium‐ion batteries is experimentally investigated and compared to modeling results, showing very good agreement for the investigated films. Heat transfer coefficients of the issued impinging nozzles are characterized and measured quantitatively and are used for the drying simulation of the gravimetric drying experiments. In situ temperature changes in the films are measured and presented using an infrared camera setup.

Payne cell gravimetric measurements in polymer‐solvent systems for diffusion coefficients and isotherm data

AbstractThe discussion focuses on the application of a Payne cell to the measurement of diffusion and solubility coefficients in polymer/solvent systems. Payne cells have, thus far, been used exclusively to measure steady‐state permeation rates of solvents. An analytical model has been developed to describe transient gravimetric sorption and desorption measurements performed with a Payne cell. The model has been validated by a complementary numerical simulation and has been applied to evaluate diffusion and solubility coefficients in two different toluene‐silicone rubber systems. The data measured using the Payne cell are found to compare very well with diffusion coefficient and isotherm data measured by traditional gravimetric sorption experiments.

Thermodynamic and Dynamic Study on the Carbon Deposition on an Iron Surface in a C–H–O System

The C–H–O ternary phase diagrams in equilibrium with graphite were developed to determine the gas compositions and boundaries for graphite formation in 500–900 °C. Thermogravimetric calculation results showed that carbon deposition was favored under the conditions of low temperature, high carbon, and low oxygen potential. The carbon deposition with reduced iron was carried out in a syngas of H2 and CO by thermal gravimetric experiments. The results showed that carbon deposition started at 400 °C, accelerated at 600–800 °C, and stopped at 1000 °C. Carbon deposition was accelerated by the presence of H2, which was increased with the CO ratio in the gas mixture, and depressed by the addition of CO2. The reduced iron with large surface area fabricated the carbon deposition. Cementite (Fe3C) was formed as intermediate that accelerated the carbon deposition rate. The C–H–O ternary phase diagrams in equilibrium with Fe3C were also provided.

Correlation of mechanical and hydration properties of soft phytoglycogen nanoparticles

Phytoglycogen nanoparticles are highly branched polymers of anhydroglucose units (AGUs) produced as soft, compact nanoparticles by sweet corn. By combining results of dialysis, ellipsometry and gravimetric analysis experiments, we constructed a master plot of the osmotic pressure Π -concentration C data for phytoglycogen nanoparticles that spans the complete range ∼ 0% w/w <C< ∼ 100 % w/w. The distinctive shape of the ΠC curve for phytoglycogen differs significantly from that of dextran, a lightly branched polysaccharide also made up of AGUs but not in the form of particles, especially near concentrations corresponding to contact between the nanoparticles. By calculating the dependence of the osmotic pressure on the volume per particle, we determined the increase in the bulk modulus of the particles with decreasing particle volume due to removal of water from the particles upon compression. This approach allowed us to quantify the strong correlation between the mechanical and hydration properties of phytoglycogen nanoparticles.

Storage time evaluation of a residue from wine industry as a microencapsulated corrosion inhibitor for 1 M HCl

The effect of a residue from wine industry was investigated as a corrosion inhibitor for API P110 steel in hydrochloric acid. The extract was characterized using Fourier-transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H NMR) and chromatography. The influence of temperature (303–333 K) and grape peel extract concentration were studied using gravimetric and electrochemical experiments. The coupon surfaces were evaluated using microscopy techniques, FTIR-ATR and the contact angle. The by-product exhibited high weight loss efficiencies at 303 K with 4.0 g/L of the extract (83.81%) even after storage. The inhibition increased with the addition of an inorganic enhancer, indicating a synergistic effect between the active compounds and maximum efficiency of 94.48%. Polarization tests indicated that the inhibitor adsorbs on anodic and cathodic regions. The surface characterization techniques confirmed the formation of an organic film and a less attacked surface was observed for the inhibited system.