Essential oil of Salvia aucheri mesatlantica as a green inhibitor for the corrosion of steel in 0.5 M H2SO4

Essential oil of aerial parts of Salvia aucheri Boiss. var. mesatlantica was obtained by hydrodistillation and analyzed by GC and GC/MS. The oil was predominated by camphor (49.59%). The inhibitory effect of this essential oil was estimated on the corrosion of steel in 0.5 M H₂SO₄ using electrochemical polarization and weight loss measurements. The corrosion rate of steel is decreased in the presence of natural oil. The inhibition efficiency was found to increase with oil content to attain 86.12% at 2 g/L. Polarization curves revealed that the oil of S. aucheri mesatlantica acts as mixed type inhibitor with a strong predominance of anodic character. The temperature effect on the corrosion behavior of steel in 0.5 M H₂SO₄ without and with the inhibitor at 2 g/L was studied in the temperature range from 303 to 343 K, the associated activation energy have been determined. The adsorption of oil on the steel surface was found to obey Langmuir’s adsorption isotherm.     

Biosorption of Ni(II) from electroplating wastewater by modified (Eriobotrya japonica) loquat bark

Biosorption of nickel ions from aqueous solutions by modified loquat bark waste (MLB) has been investigated in a batch biosorption process. The biosorbent MLB was characterized by FTIR analysis. The extent of biosorption of Ni(II) ions was found to be dependent on solution pH, initial nickel ions concentration, biosorbent dose, contact time, and temperature. The experimental equilibrium biosorption data were analyzed by three widely used two-parameters Langmuir, Temkin and Freundlich isotherm models. Langmuir and Temkin isotherm models provided a better fit with the experimental data than Freundlich isotherm model by high correlation coefficients R². The maximum adsorption capacity was 27.548 mg/g of Ni(II) ions onto MLB. The thermodynamic analysis indicated that the biosorption behavior of nickel ions onto MLB biosorbent was an endothermic process, resulting in higher biosorption capacities at higher temperatures. The negative values of ΔG° (−5.84 kJ/mol) and positive values of ΔH° (13.33 kJ/mol) revealed that the biosorption process was spontaneous and endothermic. Kinetic studies showed that pseudo-second order described well the biosorption experimental data. The modified loquat bark (MLB) was successfully used for the biosorption of nickel ions from synthetic and industrial electroplating effluents.     

AC impedance measurement of cystine adsorption at mild steel/sulfuric acid interface as corrosion inhibitor

Alternating current (AC) impedance measurements of mild steel/sulfuric acid interface in the absence and in the presence of various concentrations of cystine (Cys–Cys) have been carried out in the 100 kHz–10 mHz frequency range. The results revealed that Cys–Cys is a good and effective inhibitor for mild steel corrosion in 0.5 M H₂SO₄ and its percent inhibition efficiency changes with its concentration. Changes in impedance parameters indicated the adsorption of Cys–Cys on the mild steel surface, which was verified by scanning electron microscope (SEM) and atomic force microscope (AFM) photographs. Adsorption of Cys–Cys on mild steel surface was found to obey the Langmuir adsorption isotherm with a standard free energy of adsorption of −33.2 kJ/mol. Energy gaps for the interactions between mild steel surface and Cys–Cys molecule were found to be close to each other showing that Cys–Cys owns capacity to behave as both electron donor and electron acceptor.     

Corrosion Behavior of Carbon Steel in Lithium Bromide Solution

Weight‐loss tests and electrochemical techniques are used to study the inhibition of BTA and Na₂MoO₄ either individually or in different combinations for carbon steel in boiling 10.24 mol/L LiBr solution containing 0.07 mol/L LiOH. The result indicates the corrosion of carbon steel is effectively inhibited when BTA or Na₂MoO₄ is added to the solution individually. The adsorptions of BTA or Na₂MoO₄ on carbon steel surfaces can be well fitted to a Langmuir adsorption isotherm. The free energy of adsorption of BTA and Na₂MoO₄ are ?45.07 kJ/mol and ?40.69 kJ/mol, respectively. The corrosion rate is decreased to the minimal value, which is 8.39 μm/y, when 7.28 × 10^?4 mol/L Na₂MoO₄ and 8.39 × 10^?4 mol/L BTA are added to a 10.24 mol/L LiBr solution containing 0.07 mol/L LiOH. The inhibition mechanism of the above mixed inhibitors results from the complemental effect of the compact inner layer film composed of Fe‐BTA and the absorbed MoO₄^2? in small quantity of the active site and the outer layer. The passive film of the coordination compound and the adsorbed MoO₄^2? prevent Br^? from absorbing and effectively decrease the corrosion of carbon steel.     

Atenolol sequestration using activated carbon derived from gasified Glyricidia sepium

Activated carbon (AC) derived from gasified Glyricidia sepium woodchip (GGSWAC) was prepared using KOH and CO₂ activation via microwave radiation technique to remove atenolol (ATN) from aqueous solution. The surface area (S_BET) and total pore volume (TPV) of GGSWAC were 483.07 m²/g and 0.255 cm³, respectively. The n-BET model fits well with the isothermal data indicating a multilayer adsorption with the saturation capacity of 121, 143 and 163 mg/g at 30, 45 and 60 °C, respectively. The kinetic study showed that ATN adsorption followed Avrami model equation (R² ≅ 0.99). Based on the thermodynamic parameters, the adsorption of ATN onto GGSWAC was endothermic (ΔH_S = 234.17 kJ/mol) in the first layer of adsorption and exothermic in the subsequent layer (ΔH_L = −165.62 kJ/mol). The ATN adsorption was controlled by both diffusion and chemisorption. In continuous operation, the Thomas (R² = 0.9822) and Yoon–Nelson (R² = 0.9817) models successfully predicted the ATN adsorption.     

A combined computational & electrochemical exploration of the Ammi visnaga L. extract as a green corrosion inhibitor for carbon steel in HCl solution

Natural-based corrosion inhibitors have gained great research interest thanks to their low cost and higher performance. In this work, the chemical composition of the methanolic extract of Ammi visnaga umbels (AVU) was evaluated by gas chromatography (GC) coupled with mass spectrometry (MS) and applied for corrosion inhibition of carbon steel (CS) in 1.0 mol/L HCl using chemical and electrochemical techniques along with scanning electron microscope (SEM) and theoretical calculations. A total of 46 compounds were identified, representing 89.89% of the overall chemical composition of AVU extract, including Edulisin III (72.88%), Binapacryl (4.32%), Khellin (1.97%), and Visnagin (1.65%). Chemical (Weight loss) and electrochemical (potentiodynamic polarization curves (PPC), and electrochemical impedance spectroscopy (EIS)) techniques revealed that investigated extract can be used as an effective corrosion inhibitor for carbon steel in 1.0 mol/L HCl solution. At a low dose of 700 ppm, the inhibitory action of AVU extract reached an inhibition efficiency of 84 percent. According to polarization tests, the investigated extract worked as a mixed inhibitor, protecting cathodic and anodic corrosion reactions. The EIS test showed that upon the addition of AVU extract to HCl solution, the polarization resistance increased while the double layer decreased. SEM images showed a protected CS surface in the inhibited solution. Quantum chemical calculations by Density Functional Theory (DFT) for the main components confirmed the major role of heteroatoms and aromatic rings as adsorption sites. Molecular dynamics (MD) simulation was used to study the adsorption configuration of the main components on the Fe(1 1 0) surface. Outcomes from this study further confirmed the significant advantage of using plant-based corrosion inhibitors for protecting metals and alloys.     

Adsorption of tetracycline using CuCoFe2O4@Chitosan as a new and green magnetic nanohybrid adsorbent from aqueous solutions: Isotherm,kinetic and thermodynamic study

Utilizing a new microwave-assisted method, CuCoFe₂O₄@Chitosan (Ch) was synthesized as a very strong, magnetically separable nano-adsorbent. The magnetic nanohybrid adsorbent was characterized by FESEM (Field emission scanning electron microscopy), EDS (energy dispersive X-ray), Mapping & Linescan, BET (Brunauer-Emmett-Teller), FTIR (Fourier-transform infrared spectroscopy), XRD (X-ray diffraction analysis), TGA (Thermogravimetric analysis), and VSM (Vibrating Sample Magnetometer) techniques. Then, the adsorption process of Tetracycline (TC) was investigated. The highest percentage of pollutant adsorption on the synthetic and real samples was recorded at an initial concentration of 5 mg/L, pH 3.5, contact time of 20 min, the dose of 0.4 g/L, and temperature of 25 °C, 93.07 %, and 67%, respectively. The TC adsorption process via the synthesized magnetic nanocomposite was consistent with the Freundlich isotherm model (R² = 0.992) and pseudo-second-order kinetic (K₂ = 0.267). The outcomes of thermodynamic analyses, which included entropy changes (ΔS = 10.122 J/mol.k), enthalpy changes (ΔH = ?1.975 kJ/mol), and the Gibbs negative free energy (ΔG = ?4.992 kJ/mol), revealed that the adsorption process was spontaneous, favorable, and exothermic. The good magnetic properties allow easy separation after the adsorption operation. Finally, the efficiency of the nano-adsorbent in the removal process was 82.16% after four adsorption–desorption cycles. Some advantages of this research are a fast and green method for synthesis of adsorbent, fast kinetic, and magnetic properties to easy separation.     

Synthesis of a new class of corrosion inhibitors derived from natural fatty acid: 13‐Docosenoic acid amide derivatives for oil and gas industry

As corrosion inhibitors, a series of new amide derivatives of 13‐docosenoic acid was synthesized in yields of above 90% by reacting 13-docosenoic acid with primary and secondary aliphatic and aromatic amines. The inhibition efficiencies (%IEs) of these compounds at various concentrations for the suppression of corrosion of mild steel in 1.00 M HCl exposed for 96 h (4 days) at temperatures in the range 298–333 K were measured via gravimetric corrosion measurements. At 100 ppm, all compounds yielded satisfactory corrosion %IE in 1.00 M HCl; compounds 2 and 7 exhibited remarkable %IE of 70.0 and 74.7%, respectively. The results of gravimetric measurements further revealed that compound 7 performed excellently at 60 °C, with %IE = 96.8 at 500 ppm. Quantum chemical density functional theory (DFT) calculations helped predict that compound 7 should have more aromatic character, enabling it to serve as a donor-center for the empty d-orbital of the metal atoms, leading to higher corrosion IE. The adsorption of the inhibitor molecules on the surface of mild steel followed the Langmuir adsorption model, and the free energy of adsorption (ΔG_ads) value indicated that the inhibitors are adsorbed through a combined physisorption and chemisorption mechanism to provide effective surface coverage.     

Gravimetric,electrochemical, and morphological studies of an isoxazole derivative as corrosion inhibitor for mild steel in 1M HCl

In present study, an isoxazole derivative, namely, (Z)-4-(4-hydroxy-3-methoxybenzylidene)-3-methylisoxazol-5(4H)-one referred here as (IOD) has been studied as an environment-friendly corrosion inhibitor for mild steel (MS) in acidic medium (1 M HCl). The present work was investigated by gravimetric, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), fourier-transform infrared (FT-IR) spectroscopy techniques. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) confirmed the surface morphologies of the MS surface with and without IOD in the acid medium. The inhibition efficiency (I.E.) of IOD was increased by rising its concentration attaining maximum value (96.6%) at 300 ppm at 30 °C and decreases with increasing temperature from 30 °C to 60 °C. The adsorption of studied inhibitor followed Langmuir adsorption isotherm model. The PDP study revealed that the IOD acts as a mixed-type inhibitor with predominating anodic effect. The EIS study confirmed that increasing IOD concentration enhances the charge transfer resistance (R_ct) and then reduces the double layer capacitance (C_dl) owing to the development of a protective layer on the MS surface.     

Effects of temperature on the weathering lifetime of coated polycarbonate

The lifetime of polycarbonate (PC) coated with silicone hardcoats containing UV absorber is shorter at elevated temperatures. The activation energy (E_a) for delamination was found to be 18 ± 2 kJ/mol (4.3 ± 0.5 kcal/mol) at the 95% confidence level in this study. This E_a is the consequence of the sensitivity of the substrate and the UV absorber to temperature. The E_a for PC photodegradation was previously found to be 17-21 kJ/mol (4-5 kcal/mol). The E_a for loss of absorbance in the second-generation silicone hardcoat was found to be 28.5 ± 5.4 kJ/mol (6.8 ± 1.3 kcal/mol) at the 95% confidence level. Results are consistent with experimental findings when these activation energies are used in published predictive models. Since the E_a for coating delamination depends on the E_a of UV absorber loss, coating systems different from the one in this study will need to be investigated separately.     

Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

Effect of Artabotrys odoratissimus extract as an environmentally sustainable inhibitor for mild steel corrosion in 0.5 M H2SO4 media

Artabotrys odoratissimus inhibitory effect on mild steel (MS) corrosion in 0.5 M H₂SO₄ solution has been assessed utilizing mass loss, electrochemical potentiodynamic polarization, and impedance spectroscopy techniques. The Artabotrys odoratissimus plant has a wide range of bioactive compounds. Phytochemicals were tested for ethanolic Artabotrys odoratissimus leaves extract (AOLE) using the FeCl₃ test, Salkowaski's test, and others. Corrosion tests were conducted at varying inhibitor concentrations and temperatures. The inhibitory impact of AOLE on corrosion of MS was reported to improve with increasing concentration. Polarization experiments revealed that AOLE is a mixed kind of inhibitor and the inhibition efficacy (η_w) for MS is 93.27% for 1.25 g/L AOLE. For Electrochemical impedance spectroscopy (EIS), maximal inhibitory efficacy (η_w) was 91.62% due to AOLE adsorption on the MS surface. The obtained results using each methodology are highly consistent and closely resemble each other. The adsorption of AOLE molecules on an MS surface from the bulk of the solution causes the inhibitor's inhibition action, and the adsorption mechanism follows Langmuir adsorption isotherm. The computed $\Delta G_{ads}^o$ values ranged between ?32.919 and ?33.520 kJ mol^?1, implying a spontaneous and exothermic inhibitory action. The thermodynamic and activation parameters are often used to understand corrosion inhibition mechanisms. The comparison of corrosion product and pure extract FT-IR spectrum indicates the nature of AOLE adsorption on the MS surface. The surface morphology of MS samples was assessed using atomic force microscopy (AFM), scanning electron microscope (SEM), and contact angle techniques.     

Investigation of bio-corrosion in galvanized steel by Desulfovibrio desulfuricans and its mitigation by Butea monosperma leaf extract as green inhibitor

This work is intended to examine the microbially influenced corrosion on galvanized steel (GS) caused by sulfate-reducing bacteria (SRB). The efficacy of Butea monosperma (palash) leaf extract to mitigate the corrosion caused by Desulfovibrio desulfuricans was investigated in modified Barr's medium. Weight loss and electrochemical analysis were performed to check the corrosion rate at regular time intervals. SEM images were performed to understand the level of deterioration of the metal surfaces. Image analysis of the unprotected sample showed the presence of pits. From the gravimetric study, the maximum inhibition efficiency (IE) of 98% was obtained with 500 ppm of Palash leaf extract for the fourth-week sample. With the addition of 500 ppm of palash extract, the sulfide concentration decreases to 0 ppm from 123 ppm. Outcomes of potentiodynamic polarization (PP) studies showed that the extract disturbs the cathodic reaction significantly and moves the corrosion potential to a more negative value and IE was about 71% from PP studies. FTIR and GC-MS analysis was performed to recognize the plausible chemical compounds present in Palash leaf powder. EIS results confirmed that the resistance to corrosion increases substantially with the addition of inhibitor. The mechanism for corrosion inhibition has been proposed based on the results obtained.     

Hydrophobic interaction chromatography of proteins: Studies of unfolding upon adsorption by isothermal titration calorimetry

Heat of adsorption is an excellent measure for adsorption strength and, therefore, very useful to study the influence of salt and temperature in hydrophobic interaction chromatography. The adsorption of bovine serum albumin and β‐lactoglobulin to Toyopearl Butyl‐650 M was studied with isothermal titration calorimetry to follow the unfolding of proteins on hydrophobic surfaces. Isothermal titration calorimetry is established as an experimental method to track conformational changes of proteins on stationary phases. Experiments were carried out at two different salt concentrations and five different temperatures. Protein unfolding, as indicated by large changes of molar enthalpy of adsorption Δh_ads, was observed to be dependent on temperature and salt concentration. Δh_ads were significantly higher for bovine serum albumin and ranged from 578 (288 K) to 811 (308 K) kJ/mol for 1.2 mol/kg ammonium sulfate. Δh_ads for β‐lactoglobulin ranged from 129 kJ/mol (288 K) to 186 kJ/mol (308 K). For both proteins, Δh_ads increased with increasing temperature. The influence of salt concentration on Δh_ads was also more pronounced for bovine serum albumin than for β‐lactoglobulin. The comparison of retention analysis evaluated by the van't Hoff algorithm shows that beyond adsorption other processes occur simultaneously. Further interpretation such as unfolding upon adsorption needs other in situ techniques.     

Effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid solution

In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A₃ steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A₃ steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that ΔH, ΔS, and E_a increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process.     

Corrosion inhibition and adsorption properties of Azadirachta indica mature leaves extract as green inhibitor for mild steel in HNO3

Abstract

The corrosion inhibition and adsorption properties of Neem (Azadirachta indica – AZI) mature leaves extract as a green inhibitor of mild steel (MS) corrosion in nitric acid (HNO₃) solutions have been studied using a gravimetric technique for experiments conducted at 30 and 60°C. The results disclose that the different concentrations of the AZI extract inhibit MS corrosion and that inhibition efficiency of the extract varies with concentration and temperature. For extract concentrations studied and ranging from 9.09 to 28.57 mg/L, the maximum inhibition efficiency was 80.5 and 80.07% both at 28.57 mg/L AZI at 30 and 60°C, respectively, in 2.0 N HNO₃. The adsorption of the inhibitor on the MS surface was exothermic and consistent with the physical adsorption mechanism, best described by the Frumkin adsorption isotherm.     

Study of adsorption sites heterogeneity in zeolites by means of coupled microcalorimetry with volumetry

Adsorption of CO₂ as probe molecule on alkali-metal zeolites of MFI structure was investigated by joint volumetry–calorimetry. Consideration was given to the interpretation of the heat evolved when a probe molecule is adsorbed on the surface. In particular, the number and the strength of adsorption sites are discussed as functions of zeolite structure, concentration, and nature of extra-framework cation. The adsorption heats (q _iso) of CO₂ interaction with alkali-metal cations decrease for MFI zeolite with high Si/Al in the sequence Li⁺ > Na⁺ > K⁺ from 54 kJ/mol to 49 and 43 kJ/mol, respectively. In addition, the adsorption heats are influenced by concentration of Al in the framework. This phenomenon is attributed to formation of bridged CO₂ adsorption complexes formed between two cations. On the base of quantitative analysis of adsorption processes, presence of geminal adsorption complexes was suggested for adsorption at higher equilibrium pressures.     

向日葵盘果胶对碳钢的缓蚀性能研究

以向日葵盘为原料,利用纤维素酶制备果胶(SFP)。采用静态失重、极化曲线和交流阻抗技术研究SFP在1mol/L HCl及0.5mol/L H_2SO_4溶液中对碳钢的缓蚀性能,并探讨其在碳钢表面的吸附机理。结果表明,缓蚀效率随SFP浓度增大而增大,随温度升高而降低。在HCl和H_2SO_4溶液中,SFP的吸附方式分别服从Langmuir和Temkin等温式,属于物理吸附;极化曲线测试显示SFP是一种混合型缓蚀剂。本文的研究表明,向日葵盘果胶是碳钢的绿色高效缓蚀剂,且在HCl溶液中的缓蚀性能优于在H_2SO_4溶液中。     

First-principles study of O2 adsorption and dissociation on the CuCr2O4 (100) surface

The adsorption and dissociation of molecular oxygen on spinel CuCr₂O₄ (100) surface were carried out by first-principles calculations based on density functional theory (DFT). The calculated results indicate that the Cr site is most favorable for atomic oxygen adsorption, with an adsorption energy of 402.8 kJ/mol. For molecular oxygen adsorption, there are three types of favorable interaction modes: O₂ forms bonds with the Cu site or O₂ binds to two Cr sites or O₂ interacts with both Cu and Cr sites simultaneously. The lowest activation energy (E_a = 35.4 kJ/mol) was found through exploring possible reaction pathways for O₂ dissociation. The relationship between E_a and reaction enthalpy (ΔH) for O₂ dissociation adsorption reactions fits Brønsted-Evans-Polanyi (BEP) behavior.