Adsorption Isotherms Research Articles

Graphene oxide@chitosan for urinary sarcosine extraction in prostate cancer detection: Method development and adsorption isotherm studies

Sarcosine has emerged as a potential prostate cancer marker, yet current detection methods have limitations, necessitating the development of non-invasive approaches for early and accurate diagnosis. To develop a novel, sensitive method combining dispersive micro-solid phase extraction with high-performance liquid chromatography for sarcosine determination in urine samples. A meso-sized graphene oxide@chitosan adsorbent was synthesized via a template-free, freeze-drying method. The adsorption mechanism was investigated using Langmuir and Freundlich isotherm models, and extraction parameters were optimized for maximum efficiency. Under optimized conditions, the method showed linearity over 0.05-5 µg/mL with precision better than 10%. The adsorption data demonstrated better correlation with the Langmuir model, indicating monolayer adsorption. Regeneration studies using acetonitrile and water washing cycles demonstrated the adsorbent’s reusability for up to 5 extraction cycles, with approximately 70% retention of initial extraction capacity. The method exhibited high sensitivity and good precision using a simple setup. This approach offers a practical, non-invasive method for sarcosine determination in urine, potentially contributing to improved prostate cancer screening and monitoring. The reusability of the adsorbent enhances its economic viability and aligns with green chemistry principles, though some capacity loss occurs after multiple cycles, likely due to memory effects or structural changes in the porous framework.

Selective adsorption and synchronous reduction of Au from water with difunctional cellulose aerogel: Performance and mechanism

Here, valonia tannin and sulfhydryl functional groups were added to the cellulose aerogel from waste textiles to form a thiol-modified tannin-immobilized cellulose-based aerogel (TVTCA) with selective adsorption and outstanding reducing properties. This aerogel was then utilized to recycle Au(III) in the water. The resulting 3D TVTCA contained abundant -SH groups and phenolic hydroxyl groups and exhibited stable crystal structure and good thermal properties. TVTCA showed excellent Au (Ⅲ) adsorption performance (598.3 mg/g of maximum adsorption capacity) and strong reductivity (78 %). The adsorption process was conducted using both the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. In addition, TVTCA displayed excellent anti-interference ability. Even though the coexisting ions concentration was as high as 100 mmol/L, TVTCA still owned a high Au adsorption capacity (178.91–224.14 mg/g) and selectivity factor (29.16–2629.34), which was much higher than valonia tannin-immobilized cellulose-based aerogel (VTCA). Furthermore, the recycling of Au with TVTCA mainly included adsorption and in-situ reduction processes. The mechanisms involved the electrostatic interaction and chelation effects, which were ascribed to the introduced sulfhydryl groups. Meanwhile, the in-situ Au reduction was mainly caused by the studies showing that the high adsorption capacity of TVTCA was owing to the phenolic hydroxyl groups on the introduced valonia tannin. All the findings would provide a new way to achieve the recycling of precious metals from wastewater by using valuable cotton waste.

Investigation of the adsorption process of methylene blue on diatomite from a kinetic and thermodynamic perspective

The adsorption of methylene blue on diatomite has been studied. Kinetics, thermodynamics and adsorption isotherms were used to identify retention mechanisms. The experiments, carried out in batch mode, for the determination of the kinetics, were carried out after adjustment of the parameters influencing the system, such as the pH, the temperature, the mass of adsorbent. The adsorption process of methylene blue onto diatomite is effectively represented by the Langmuir model, which indicates an adsorption capacity of roughly 166.66 mg/g. This is confirmed by the fact that the correlation coefficient exceeds that obtained with the Freundlich model; furthermore, the separation factor indicates that this adsorption is favorable. The results obtained were modeled according to the kinetic equations of the pseudo-first order, pseudo-second order, as well as that related to intraparticle diffusion. The experimental results of the global reaction are perfectly tunable to the pseudo-second order, with very large regression coefficients. Thermodynamics and adsorption isotherms predict the passage of a spontaneous endothermic surface reaction.

Enhancing Methylene Blue Adsorption Performance of Ti3C2Tx@Sodium Alginate Foam Through Pore Structure Regulation.

Pore structural regulation is expected to be a facile way to enhance the adsorption performance of MXene. In this work, spherical foam composites consisting of Ti3C2Tx and sodium alginate (SA) were synthesized via a vacuum freeze-drying technique. By varying the solution volume of Ti3C2Tx, four distinct Ti3C2Tx@SA spherical foams with honeycomb-like and lamellar structures with a pore diameter in the range of 100-300 μm were fabricated. Their methylene blue (MB) adsorption performances were then systematically compared. The results revealed that the honeycomb-like porous-structured spherical foams have a significantly higher adsorption capacity than their lamellar counterparts. Notably, the Ti3C2Tx@SA honeycomb-like porous foam exhibited a remarkable maximum adsorption capacity (qm) of 969 mg/g, positioning it at the forefront of MB adsorbent materials. Respective analysis of the adsorption kinetics, thermodynamics, and isotherm model indicated that this MB adsorption of Ti3C2Tx@SA honeycomb-like porous foam is characterized to be a physical, endothermic, and monolayer adsorption. The Ti3C2Tx@SA honeycomb-like porous foam also demonstrated excellent resistance to ion interference and good reusability, further attesting to its substantial potential for practical applications. X-ray photoelectron spectroscopy (XPS) analysis was employed to elucidate the adsorption mechanism, which was found to involve the synergistic effect of electrostatic adsorption and amidation reaction. This work not only offers new avenues for the development of high-performance adsorption materials but also provides crucial insights into the structural design and performance optimization of porous materials.

Synthesis of a Novel Magnetic Biochar from Lemon Peels via Impregnation-Pyrolysis for the Removal of Methyl Orange from Wastewater

This research examined the elimination of methyl orange (MO) utilizing a novel magnetic biochar adsorbent (MLPB) derived from lemon peels via an impregnation-pyrolysis method. Material characterization was conducted using SEM, XRD, TGA, FTIR, and nitrogen adsorption isotherms. SEM-EDX analysis indicates that MLPB is a homogeneous and porous composite comprising Fe, O, and C, with iron oxide uniformly dispersed throughout the material. Also, MLPB is porous with an average pore diameter of 4.65 nm and surface area value (111.45 m2/g). This study evaluated pH, MO concentration, and contact time to analyze the adsorption process, kinetics, and isothermal behavior. Under optimal conditions, MLPB was able to remove MO dye from aqueous solutions with an efficiency of 90.87%. Results showed optimal MO removal at pH 4, suggesting a favorable electrostatic interaction between the adsorbent and dye. To ascertain the adsorption kinetics, the experimental findings were compared using several adsorption models, first- and second-orders, and intra-particle diffusion. According to the findings, the pseudo-second-order model described the adsorption kinetic promoting the formation of the chemisorption phase well. Modeling of intra-particle diffusion revealed that intra-particle diffusion is not the only rate-limiting step. A study involving isothermal systems showed that Langmuir is a good representation of experimental results; the maximum adsorption capacity of MLPB was 17.21 mg/g. According to the results, after four cycles of regeneration, the produced magnetic material regained more than 88% of its adsorption ability.

Preparation and Adsorption Properties of a Three-Dimensional Superhydrophilic Mercury-Ion-Imprinted Polymer with Dual Recognition Site Based on MoS2/SBA-15.

Water pollution resulting from Hg(II) ions has garnered significant global concern for public health. The flexibility and simplicity of design, cost savings, and ease of operation with adaptive designs provide adsorption with a considerable advantage over other processes. However, MoS2 is hydrophobic in nature, which limits its efficiency in the removal of Hg(II) ions from water. Therefore, the incorporation of hydrophilic SBA-15 as supporting material, combined with a nanoflower-like layered MoS2 and its highly reactive exposed edges, produces hydrophilic properties that effectively eliminate Hg(II) from water . A mercury-ion-imprinted polymer (Hg(II)-IIP) was synthesized on the MoS2/SBA-15 surface using N-allylthiourea (ATU) as a functional monomer to enhance material selectivity and create dual recognition sites. Characterization investigation using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle showed the successful synthesis of Hg(II)-IIP, excellent hydrophilicity, and close interaction between MoS2 and SBA-15. The maximum adsorption capacity of Hg(II)-IIP for Hg(II) under optimized adsorption conditions was 567.78 mg·g-1 in 90 min, which was 6 times greater than that of the IIP solely based only on SBA-15, and followed by pseudo-second-order and aligned more closely fits with the Langmuir adsorption isotherm. Furthermore, the adsorption capacity of the synthesized Hg(II)-IIP was greater than that of three other common monomers IIP. Hg(II)-IIP possesses a strong ability to regenerate, while also showing better selectivity for Hg(II) in the presence of other interfering ions, indicating its robust anti-interference capability in the multivariate mixed solution. The analysis of the actual sample indicated that Hg(II)-IIP attained recoveries between 97.92 and 100.28% in water samples. Theoretical calculations using density functional theory (DFT) and frontier molecular orbital (FMO) indicated that the binding energy of the sulfur atom forming a tetra-ligand with Hg(II) on ATU was 0.6511 eV greater than that of a diligand. The energy gap was determined to be 0.1550 eV, supporting the preference for S-Hg tetra-ligand adsorption.

Effects of particle size and aging on heavy metal adsorption by polypropylene and polystyrene microplastics under varying environmental conditions

Microplastics have become a major environmental issue because of their widespread presence and tendency to adsorb heavy metals, which can have harmful effects on aquatic ecosystems and human health. The present study investigates the adsorption mechanisms of Pb2+ and Cu2+ ions on both pristine and artificially aged microplastics (MPs) made of polystyrene (PS) and polypropylene (PP). Furthermore, the influence of MP size on the adsorption capacity under different environmental conditions was evaluated. According to the characterization of MPs, aging leads to physical damage and an increase in the number of oxygen-containing functional groups on their surface. The experimental results highlight the significantly higher adsorption ability of smaller and aged MPs compared with that of pristine MPs for both the heavy metal ions. The pseudo-second-order equation provided a better fit for the adsorption kinetics study (R2 = 0.95), suggesting that chemisorption governs the rate-limiting phase in the adsorption mechanism on the MP surfaces. The concordance between the adsorption isotherm model and Freundlich model (R2 > 0.95) indicated a predominance of multilayer adsorption. The environmental factors such as pH, humic acid, temperature, and SO42- concentration significantly affected the adsorption of Pb2⁺ and Cu2⁺ onto PP and PS MPs. These variables play a crucial role in determining the nature of the interactions between heavy metal ions and the microplastic particles under diverse environmental conditions. Electrostatic interactions, surface complexation and van der Waals forces were identified as two factors that could either improve or diminish the metal ion adsorption capacity of MPs.

Adsorption of CO2, CH4 and H2 onto zeolite 13 X: Kinetic and equilibrium studies

Adsorption equilibrium and kinetics of CO2, H2 and CH4 on zeolite 13 X were carried out using the volumetric method. The zeolite 13 X was characterized via XRD, SEM and N2 adsorption-desorption. Adsorption isotherms of various gas were investigated over a full range of temperatures at 298, 308 and 313 K. Langmuir's equilibrium model and the heat of adsorption was used to correlate the adsorption isotherms over a wide range of pressure. A classical micropore diffusion approach was applied to investigate the kinetic adsorption. At 298 K, the selectivity of CO2/H2 and CO2/CH4 of the zeolite 13 X was 16.52 and 62.61, respectively. However, zeolite 13 X is one of the most suitable adsorbents for CO2 and CH4 storage, since it has a very high adsorption capacity for both gases. The influence of gas pressure on diffusivity for various absorber-adsorbent systems has been examined. The adsorption experiments with gas mixtures such as H2, CO2 and CH4 on 13 X zeolite show that this adsorbent has potential application in the gas separation and purification process.

Innovative Surface Plasmon Resonance Aptasensor for Detecting Cocaine in Human Urine

This study describes the development of an optical-based surface plasmon resonance (SPR) aptasensor for the detection of cocaine. The aptasensor was prepared by first attaching gold nanoparticles to a clean SPR chip surface, followed by the addition of an aptamer to create a modified surface. This surface was characterized using contact angle and atomic force microscopy, revealing surface roughness values of 0.28 nm and 28.12 nm for the blank and modified surfaces, respectively. The detection of cocaine was carried out in the concentration range of 1 ng/mL to 1000 ng/mL, with a detection time of approximately 8 min and a cocaine limit of detection (LOD) of 0.43 ng/mL. Repeatability studies were conducted, and the stability of the signal response was examined at a concentration of 200 ng/mL. Adsorption isotherm models, including Scatchard, Langmuir, and Freundlich models, were calculated to assess the surface homogeneity of the SPR aptasensor chip, with the results indicating compatibility with the Langmuir isotherm model.

Microwave Irradiation-Assisted Synthesis of Anisotropic Crown Ether-Grafted Bamboo Pulp Aerogel as a Chelating Agent for Selective Adsorption of Heavy Metals (Mn+)

Crown ether is widely used in water purification because of its ring structure and good selective adsorption of specific heavy metals. However, its high cost and difficulty in recycling limit the purification of heavy metals in water. The anisotropic [2,4]-dibenzo-18-crown-6-modified bamboo pulp aerogel (DB18C6/PA) is successfully synthesized by microwave irradiation and directional freezing technology. The physical and chemical properties of DB18C6/PA are analyzed by FTIR, XPS, SEM, TEM, TGA, surface area and porosity analyzers. Single or multivariate systems containing Pb2+, Cu2+ and Cd2+ are used as adsorbents. The effects of the DB18C6 addition amount, pH, initial concentration and adsorption temperature on the adsorption of DB18C6/PA are systematically explored. Pseudo-first-order kinetic models, pseudo-second-order kinetic models and the isothermal adsorption models of Langmuir and Freundlich are used to fit the experimental data. The adsorption selectivity is analyzed from the distribution coefficient and the separation factor, and the adsorption mechanism is discussed. The results show that anisotropic DB18C6/PA has the characteristics of 3D directional channels, high porosity (97.67%), large specific surface area (103.7 m2/g), good thermal stability and regeneration (the number of cycles is greater than 5). The surface has a variety of functional groups, including a hydroxyl group, aldehyde group, ether bond, etc. In the single and multivariate systems of Pb2+, Cu2+ and Cd2+, the adsorption process of DB18C6/PA conforms to the pseudo-second-order kinetic model, and the results conform to the Freundlich adsorption isothermal model (a few of them conformed to the Langmuir adsorption isothermal model), indicating that chemical adsorption and physical adsorption are involved in the adsorption process, and the adsorption process is a spontaneous endothermic process. In the single solution system, the maximum adsorption capacities of Pb2+, Cu2+ and Cd2+ by DB18C6/PA are 129.15, 29.85 and 27.89 mg/g, respectively. The adsorption selectivity of DB18C6/PA on Pb2+, Cu2+ and Cd2+ is in the order of Pb2+ >> Cu2+ > Cd2+.

Optimisation of mercury adsorption by ZIF-8 from aqueous solutions through response surface methodology

ABSTRACT Mercury is one of the most toxic heavy metals. Various techniques have been used to remove it from water sources. Among these, adsorption is a low-cost and effective method to remove mercury even in very low concentrations. One of the adsorbents that has gained considerable popularity recently is the zeolite imidazolate framework-8 (ZIF-8). In this study, after the synthesis of ZIF-8, its properties were determined using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission electron microscopy (FESEM). Temperature (25–61 °C), contact time (5–85 min), adsorbent dosage (0.1–0.9 g/L), pH (2–10), and initial mercury concentration (24- mg/L) were investigated. The optimal conditions for the adsorption method were determined using the response surface methodology (RSM). The optimal conditions for mercury elimination included a primary mercury concentration of 4 mg/L, a temperature of 61°C, adsorbent dose (0.5 g/L), and a pH of 7; the elimination efficiency under these conditions was 91.66%. The adsorption equilibrium data were analysed using Langmuir and Freundlich isotherm models, and the Langmuir model was found to be consistent with the adsorption isotherm (R2 = 0.9363). The adsorption kinetics closely matched the pseudo-second-order model (R2 = 0.9998). These results indicate that the nanoporous adsorbent ZIF-8 can successfully eliminate mercury from aqueous environments.

A comprehensive study on methylene blue removal via polymer and protein nanoparticle adsorbents

Water pollution, particularly from industrial contaminants such as dyes, is a significant global concern. Various technologies, including nanoscale materials, are employed for water and wastewater treatment. Among these, adsorption process as an effective method due to its simplicity, cost-effectiveness, and reliability. This study comprised both theoretical and experimental phases. Initially, computer simulations were utilized to evaluate the interaction between methylene blue and three selected nanoparticles, ultimately choosing Bovine Serum Albumin protein nanoadsorbent based on energy considerations. Subsequently, adsorption experiments were conducted using this nanosorbent. The results indicated a maximum dye removal efficiency of 69% under the conditions of pH 11, an initial dye concentration of 100 mg/L, an adsorbent dose of 0.5 g/L, a contact time of 60 min, and an optimal temperature of 25 °C. The maximum adsorption capacity under optimal conditions was found to be 38.52 mg/g. Additionally, the adsorption isotherm followed the Langmuir equation, and the kinetics adhered to the pseudo-second-order model.

Gas Content and Geological Control of Deep Jurassic Coalbed Methane in Baijiahai Uplift, Junggar Basin

Deep coalbed methane (CBM) resources are abundant in China, and in the last few years, the country’s search for and extraction of CBM have intensified, progressively moving from shallow to deep strata and from high-rank coal to medium- and low-rank coal. On the other hand, little is known about the gas content features of deep coal reservoirs in the eastern Junggar Basin, especially with regard to the gas content and the factors that affect it. Based on data from CBM drilling, logging, and seismic surveys, this study focuses on the gas content of Baijiahai Uplift’s primary Jurassic coal seams through experiments on the microscopic components of coal, industrial analysis, isothermal adsorption, low-temperature CO2, low-temperature N2, and high-pressure mercury injection. A systematic investigation of the controlling factors, including the depth, thickness, and quality of the coal seam and pore structure; tectonics; and lithology and thickness of the roof, was conducted. The results indicate that the Xishanyao Formation in the Baijiahai Uplift usually has a larger gas content than that in the Badaowan Formation, with the Xishanyao Formation showing that free gas and adsorbed gas coexist, while the Badaowan Formation primarily consists of adsorbed gas. The coal seams in the Baijiahai Uplift are generally deep and thick, and the coal samples from the Xishanyao and Badawan formations have a high vitrinite content, which contributes to their strong gas generation capacity. Additionally, low moisture and ash contents enhance the adsorption capacity of the coal seams, facilitating the storage of CBM. The pore-specific surface area of the coal samples is primarily provided by micropores, which is beneficial for CBM adsorption. Furthermore, a fault connecting the Carboniferous and Permian systems (C-P) developed in the northeastern part of the Baijiahai Uplift allows gas to migrate into the Xishanyao and Badaowan formations, resulting in a higher gas content in the coal seams. The roof lithology is predominantly mudstone with significant thickness, effectively reducing the dissipation of coalbed methane and promoting its accumulation.

Synthesis of Co3O4 Nanoparticles Using Ananas Comosus Peel Extract for Cr6+ Ion Adsorption and Antibacterial Applications

AbstractWater contamination, caused by both point and nonpoint sources, alongside the prevalence of diseases caused by bacteria, represents a significant global challenge. In this work, cobalt oxide nanoparticles (Co3O4 NPs) were synthesized using various volume ratios such as 1:1, 1:2, and 2:1 of cobalt nitrate hexahydrate as salt precursor solution and Ananas comosus peel extract. The synthesized NPs were used as a high surface area nanoadsorbent for removal of Cr6+ from aqueous solution and antibacterial activity against drug‐resistant bacterial strains applications. The TGA–DTA analysis confirms that Co3O4 NPs were thermally stable above 500 °C. The calculated average sizes were found to be 12.58, 13.40, and 22.05 nm for the 1:1, 1:2, and 2:1 ratios, respectively. The SEM–EDS analysis with TEM–HRTEM and SAED validated that Co3O4 NPs were spherical‐shaped without impurities. The band gap energy and the specific surface area of the 1:1, 1:2, and 2:1 Co3O4 NPs were calculated as 3.33, 2.95, and 2.70 eV and 24.7, 23.7, and 22.5 m2/g, respectively. Functional group analysis confirms the presence of numerous secondary metabolites within the peel extract. Cyclic voltammetry coupled with EIS proves the enhanced electrochemical properties of synthesized Co3O4. The Co3O4 (1:1) NPs exhibited higher adsorption efficiency (95%) toward Cr6+ removal and were found to be fit with pseudo‐second‐order kinetics and also with both the Langmuir and Freundlich adsorption isotherm. The maximum (13 mm) zone of inhibition was achieved against Staphylococcus aureus and Streptococcus pyogenes by Co3O4 (1:2) NPs.

Enhanced Fenton-Photocatalytic Degradation of Rhodamine B over Cobalt Ferrite Nanoparticles Synthesized by a Polyvinylpyrrolidone-Assisted Grinding Method.

A simple grinding method using polyvinylpyrrolidone (PVP) as a capping agent is introduced to synthesize CoFe2O4 nanoparticles. The effects of calcination temperature (ranging from 450 to 850 °C) on the structural, morphological, physical, and optical properties of the materials are investigated using various techniques, including thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), N2 adsorption isotherm, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), and vibrating sample magnetometry (VSM). The presence of PVP significantly suppresses the agglomeration of the materials, resulting in a nanocrystalline size of 18 nm for a sample calcined at 650 °C, which is approximately 38% smaller than that of the sample synthesized without PVP. Among the materials studied, the sample calcined at 650 °C exhibits unique properties, including optimal average pore size, specific surface area, and band gap energy, contributing to its superior photocatalytic degradation of rhodamine B via the Fenton reaction. Systematic experiments are performed to investigate the effects of pH, catalyst dosage, dye, and H2O2 concentrations and competitive anions on the rhodamine B degradation. Additionally, the Fenton photodegradation of RhB on CoFe2O4 is well-fitted to the first-order kinetic model. The redox pairs of Co(III)/Co(II) and Fe(III)/Fe(II) in the CoFe2O4 spinel structure might facilitate the formation of Fenton radicals, contributing to the decomposition of RhB through a proposed four-step mechanism. Notably, the material exhibits a strong magnetic response and maintains its excellent performance over five cycles, demonstrating the high potential for reusability as a photocatalyst.

Cu-ZnO/CuO porous heterostructures for adsorption of lead ion

The pure ZnO and Cu-ZnO/CuO (CuZC) heterostructures had been successfully synthesized using an orange fruit peel extract-based solution combustion synthesis approach. The XRD result revealed the wurtizite phase structure of ZnO NPs with a crystallite size of 12 nm for the CuZC heterostructures. The indirect UV–vis-DRS analysis revealed the band gap energy of ZnO NPs and CuZC heterostructure to be 3.16 and 2.95 eV, respectively. Porous morphology and absence of impurities were confirmed from the FESEM-EDS and TEM/HRTEM analyses. The lead (Pb) ion adsorption potential of NPs was analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES) technique. The removal efficiency for CuZC heterostructure at an initial Pb ion concentration of 20 mg/L is 96.3 %. Based on the adsorption kinetics and isotherm models fitting value, dominance of the chemisorption adsorption process was confirmed. The doped NPs have the potential to be used as an effective and favorable adsorbent material for remediation of heavy metal ions from water solutions.

Electrochemical study and modeling of an innovative pyrazole carboxamide derivative as an inhibitor for carbon steel corrosion in acidic environment.

The impact of N,1-dibenzyl-5-methyl-1H-pyrazol-3-carboxamide (BPC) on the carbon steel (CS) corrosion in hydrochloric acid (1M) was studied in this work, considering concentration and temperature effects. Electrochemical investigation indicated that BPC functions as a mixed-type inhibitor. For an optimal BPC concentration of 125ppm, the inhibition efficiency of 91.55% was obtained at 298K. According to adsorption isotherm of Langmuir, the BPC adheres to the CS with standard adsorption free energy (ΔG°ads) of - 26.76kJmol-1. Furthermore, the calculation of dissolution activation parameters revealed an increase in energy (Ea) from 46.48 to 94.97kJmol-1, an elevation in the enthalpy (∆Ha) from 43.89 to 92.37kJmol-1, and a rise in the entropy (∆Sa) from - 91.17 to 51.43Jmol-1K-1 in the presence of 125ppm of BPC. The experimental results were confirmed by quantum chemistry calculations based on density functional theory (DFT) and molecular simulations using the Monte Carlo method. These theoretical approaches also allowed for a comparison of the inhibitory performances of BPC with its protonated form, BPCH, the latter being found more effective. Moreover, the study of the radial distribution function g(r) predicted that the nature of the bond formed with the steel surface is of a chemical type.

2-Amino-6-methylbenzothiazole as corrosion inhibitor for low carbon steel in acidic solution: Experimental and theoretical studies

The corrosion susceptibility of S235 steel samples in 1 M HCl solution, with and without addition of 2-amino-6-methylbenzothiazole (AMBT) was evaluated using weight loss (WL), chronopotentiometry, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) techniques. The corrosion inhibition efficiency of AMBT was investigated at 298 to 318 K, with and without addition of 0.5 wt% KI. The highest corrosion inhibition efficiency (i.e. 83.30 %) was achieved upon addition of 5 mM AMBT. PD curve measurements after 24 h immersion revealed that AMBT behaves as a mixed-type inhibitor, predominantly affecting the cathodic corrosion reaction. Thermodynamic calculations showed that AMBT adheres to the Langmuir adsorption isotherm. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) was used to confirm the adsorption of AMBT, while its influence on the morphology of the S235 steel samples was also investigated by scanning electron microscopy (SEM). Density Functional Theory (DFT) calculations, along with Monte Carlo (MC) and Molecular Dynamics (MD) simulations, were employed to investigate AMBT’s corrosion inhibition behaviour at the molecular level. The simulations confirmed that AMBT strongly adsorbs on the Fe(110) surface through a combination of physisorption and chemisorption mechanisms. This study offers detailed insights into AMBT’s effectiveness as a corrosion inhibitor

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.

Inspired corrosion resistance of copper mediated by multiple ethoxy units linker included indazole based bis-Schiff base dyes in NaCl solution

In this study, hydrophilic multiple ethoxy units linkage chain included bis-Schiff base dyes (SBs 1–3) were designed and synthesized for strengthening corrosion resistance of copper in NaCl solution. The corrosion resistance and corrosion inhibition mechanism of the target dyes for copper were investigated in 3.0 wt% NaCl solution. The adsorption of these dyes on copper surface was revealed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) revealed the adsorption of these dyes containing CN double bonds on copper surface, achieving excellent corrosion inhibition efficiency. The electrochemistry shows that the dyes were able to inhibit the corrosion of copper in sodium chloride solution, and the corrosion inhibition efficiency reached the peak value at a concentration of 1.00 mM. It is noted that the corrosion inhibition efficiency increased with the number increase of ethoxy units. The kinetic potential polarization curves indicate that the dyes were anodic corrosion inhibitors, which could inhibit the anodic reaction process of corrosion. The adsorption of corrosion inhibitor these dyes on copper surface followed Langmuir isothermal adsorption model.