scholarly journals Inhibition of Aluminium Corrosion in 1.0 M HCl by Caffeine: Experimental and DFT Studies

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
R. H. B. Beda ◽  
P. M. Niamien ◽  
E. B. Avo Bilé ◽  
A. Trokourey
Keyword(s):  
Experimental Data ◽  
Hydrochloric Acid ◽  
Quantum Chemical ◽  
Inhibition Efficiency ◽  
Langmuir Model ◽  
Dft Studies ◽  
Metal Dissolution ◽  
Adsorption Model ◽  
Adsorption Parameters ◽  
Insight Into

Aluminium corrosion inhibition in 1.0 M hydrochloric acid solution by caffeine has been studied using mass loss technique and quantum chemical calculations based on DFT. The inhibition efficiency was found to increase with increasing concentration of caffeine but decreases with a rise in temperature. The molecule shows the highest inhibition efficiency of 74% at 10−2 M for T=303 K. The experimental data were used to fit isotherms including Langmuir, Temkin, Freundlich, and El-Awady. The best fits were obtained with the Langmuir model and the kinetic-thermodynamic adsorption model of El-Awady. However, it was found that the adsorption parameters suit well with the isotherm of El-Awady which was chosen as the appropriate isotherm. To distinguish between physisorption and chemisorption, the Dubinin-Radushkevich adsorption model was used. The thermodynamic parameters governing the adsorption of caffeine onto aluminium and that of the metal dissolution were calculated and discussed. DFT study gave further insight into the mechanism of the inhibiting action of caffeine.

Studi Komparasi Model Langmuir, Freundlich dan Emzha untuk Biosorpsi Beberapa Ion Logam

2019 ◽  
Vol 4 (2) ◽  
pp. 141
Author(s):  
Rahmiana Zein ◽  
Zulfi Zulfi ◽  
Riza Nurafni
Keyword(s):  
Experimental Data ◽  
Metal Ions ◽  
Research Method ◽  
Langmuir Model ◽  
Coefficient Of Determination ◽  
Original Form ◽  
Adsorption Model ◽  
Average Coefficient ◽  
Two Stages

<p><em>Telah dilakukan studi komparasi untuk menguji keandalan model EMZHA dibandingkan model Langmuir dan Freunlich dalam penyerapan ion logam Cu(II), Cd(II) dan Pb(II) oleh beberapa biosorben. Model EMZHA adalah model adsorbsi baru yang diusulkan oleh peneliti Indonesia sebagai upaya mendapatkan model yang lebih bersifat universal (berlaku untuk semua tipe data) sehingga dapat digunakan untuk mengungkap mekanisme adsorbsi secara lebih lengkap dan mendasar. Model Langmuir dan Freunlich dipillih sebagai pembanding karena kedua model ini paling banyak digunakan dan memiliki karakter yang cenderung berlawanan. Penelitian ini digunakan data ekperimen dalam bentuk aslinya,  tidak diubah kedalam bentuk linier terlebih dahulu, dengan tujuan untuk menghindari error yang timbul akibat proses linierisasi. Regresi yang digunakan adalah regresi non linier. Metode penelitian ini dibagi dalam dua tahapan yaitu tahap pengumpulan data eksperimen yang berasal dari berbagai penelitian adsorbsi ion logam berat oleh berbagai biosorben dan pengolahan data komparasi model. Pengusul model EMZHA telah melaporkan keandalan prediksi model ini untuk penyerapan beberapa ion logam tapi hanya menggunakan satu jenis biosorben, yaitu kulit buah atap, sedangkan penelitian ini menggunakan 11 biosorben yang berbeda. Pada penelitian ini berhasil dibuktikan bahwa model EMZHA memiliki koefisien determinasi rata-rata 0,9034 yang lebih tinggi dari rata-rata koefisien determinasi model Langmuir (0,8485) dan Freundlich (0,8483).</em></p><p><em><br /></em></p><p><em><em>Comparative studies have been conducted to test the reliability of the EMZHA model compared to the Langmuir and Freunlich models in the absorption of Cu (II), Cd (II) and Pb (II) metal ions by several biosorbents. The EMZHA model is a new adsorption model proposed by Indonesian researchers in an effort to obtain a more universal model (applicable to all types of data) so that it can be used to uncover the mechanism of adsorption more fully and fundamentally. Langmuir and Freunlich's models are chosen as a comparison because these two models are the most widely used and have opposing characters. This study used experimental data in its original form, not converted into linear form first, with the aim of avoiding errors arising from the linearization process. The regression used is non linear regression. This research method is divided into two stages, namely the stage of collecting experimental data derived from various studies of adsorption of heavy metal ions by various biosorbents and the processing of comparative data models. Proponents of the EMZHA model have reported the reliability of the prediction of this model for the absorption of several metal ions but only use one type of biosorbent, namely the skin of the roof, while this study uses 11 different biosorbents. In this study successfully proved that the EMZHA model has an average determination coefficient of 0.9034 which is higher than the average coefficient of determination of the Langmuir model (0.8485) and Freundlich (0.8483).</em></em></p>

scholarly journals Quantum chemical elucidation on corrosion inhibition efficiency of Schiff base: DFT investigations supported by weight loss and SEM techniques

2020 ◽  
Vol 15 (2) ◽  
pp. 202-209 ◽  
Author(s):  
Ahmed Al-Amiery ◽  
Taghried A Salman ◽  
Khalida F Alazawi ◽  
Lina M Shaker ◽  
Abdul Amir H Kadhum ◽  
...  
Keyword(s):  
Weight Loss ◽  
Schiff Base ◽  
Hydrochloric Acid ◽  
Corrosion Inhibition ◽  
Quantum Chemical ◽  
Density Functional ◽  
Inhibition Efficiency ◽  
Chemical Calculation ◽  
Acid Environment ◽  
Inhibition Performance

Abstract The corrosion inhibition of Schiff base, namely 2-((2-hydroxy-5-methoxybenzylidene)amino)pyridine (HMAP), for mild steel (MS) in a 1 M hydrochloric acid environment was investigated by means of weight loss and scanning electron microscopy techniques. Quantum chemical calculation based on density functional theory (DFT) was carried out on HMAP. Results illustrated that HMAP is a superior inhibitor for the corrosion of MS in 1.0M hydrochloric acid environment, and inhibition efficiency is higher than 90.0% at 0.5 g/L HMAP. Inhibition performance increases with regard to concentration increase and inhibition performance decreases when raising temperature. Adsorption of the inhibitor on the MS surface followed Langmuir adsorption isotherm and the value of the free energy of adsorption; ΔGads indicated that the adsorption of HMAP was a physisorption/chemisorption process. The DFT refers to perfect correlation with methodological inhibition performance.

scholarly journals Adsorption of cellulases onto sugar beet shreds and modeling of the experimental data

2014 ◽  
pp. 119-128
Author(s):  
Darjana Ivetic ◽  
Radovan Omorjan ◽  
Mirjana Antov
Keyword(s):  
Experimental Data ◽  
Sugar Beet ◽  
Langmuir Model ◽  
Steam Pretreatment ◽  
Dilute Acid ◽  
Adsorption Parameters ◽  
Adsorption Models ◽  
Adsorbed Proteins ◽  
Process Productivity

This study investigated the adsorption of cellulases onto sugar beet shreds. The experiments were carried out using untreated, as well as dried and not dried dilute acid and steam pretreated sugar beet shreds at different initial enzyme loads. Both dilute acid and steam pretreatment were beneficial in respect of cellulases adsorption providing 8 and 9 times higher amounts of adsorbed proteins, respectively, in comparison to the results obtained with the untreated substrate. Although the use of higher solids load enabled by drying of pretreated substrates, could be beneficial for process productivity, at the same time it decreases the adsorption of enzymes. The obtained experimental data were fitted to five adsorption models, and the Langmuir model having the lowest residual sum of squares was used for the determination of adsorption parameters which were used to calculate the strength of cellulases binding to the substrates.

scholarly journals TENOXICAM PERFORMANCES FOR ALUMINIUM CORROSION INHIBITION IN 2M H2SO4: EXPERIMENTAL AND QUANTUM CHEMICAL APPROACHES

2021 ◽  
Vol 9 (07) ◽  
pp. 654-667
Author(s):  
Kalifa Mariko ◽  
◽  
Donourou Diabate ◽  
Paulin Marius Niamien ◽  
◽  
...  
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Low Temperature ◽  
Quantum Chemical ◽  
Inhibition Efficiency ◽  
Adsorption Process ◽  
Molecular Descriptors ◽  
Good Reliability ◽  
Increasing Temperature ◽  
Global And Local

The inhibiting performances of Tenoxicam against aluminium corrosion in 2M H2SO4 have been tested. The results show thatinhibition efficiency increases withincrease in tenoxicam concentration,but decreases with increasing temperature. The experimental data show that the adsorption process follows the Villamil isotherm. The thermodynamic adsorption and activationfunctions were determined and analysed. The adsorption of the molecule onto the aluminium surface is an exothermic and spontaneous process. The Adejo-Ekwenchi isotherm indicatesa mixed adsorption type, but essentially physisorption at low temperature and chemisorption at high temperature. The global and local molecular descriptors confirmedthe existence of a mixed adsorption type.The QSPR studies based on two sets of energetic molecular parameters ( , ) and ( show a good reliability between inhibition efficiency and the mentioned descriptors.

Quantum-Chemical Insight Into Mechanism of Combined Intra-Intermolecular Cycloaddition

2004 ◽  
Vol 69 (1) ◽  
pp. 231-241 ◽  
Author(s):  
Petr Kulhánek ◽  
Milan Potáček ◽  
Jaroslav Koča
Keyword(s):  
Experimental Data ◽  
Reaction Mechanisms ◽  
Quantum Chemical ◽  
Activation Barrier ◽  
Probable Mechanism ◽  
Basis Set ◽  
Rate Determining Step ◽  
B3lyp Level ◽  
Opposite Sequence ◽  
Insight Into

Two different reaction mechanisms of a mixed criss-cross cycloaddition with opposite sequence of reaction steps, intra-intermolecular and inter-intramolecular, were explored by quantum-chemical calculations at the MP2 and B3LYP levels of theory and with cc-pVDZ basis set. It was found that the rate-determining step in the both mechanisms is the first step regardless of the mechanism. The Gibbs activation barrier of the intramolecular step of the intra-intermolecular sequence is by 10.4 kcal mol-1 lower than that of the intermolecular step of the inter-intramolecular sequence at the MP2 level of theory and almost the same at the B3LYP level of theory. This together with known experimental data confirms that the intra-intermolecular sequence is the most probable mechanism.

scholarly journals Crystal Structure, Thermodynamic Properties and DFT Studies of 5,6-dimethyl-1H-benzo[d]imidazol-3-ium 3-((2,4-dioxo-1,5-dioxaspiro[5.5]undecan-3-ylidene)methyl) -2,4-dioxo-1,5-dioxaspiro[5.5]undecane Hydrate

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1393
Author(s):  
Wulan Zeng ◽  
Xia Wang ◽  
Yunju Zhang
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Experimental Data ◽  
Thermodynamic Properties ◽  
Water Molecule ◽  
Quantum Chemical ◽  
Dft Studies ◽  
Ft Ir ◽  
Net Framework ◽  
Quantum Chemical Computations

A new 1,5-dioxaspiro[5.5] derivative coupled with a benzimidazole moiety: 5,6-dimethyl-1H-benzo[d]imidazol-3-ium 3-((2,4-dioxo-1,5-dioxaspiro[5.5]undecan-3-ylidene) methyl) -2,4-dioxo-1,5-dioxaspiro[5.5]undecane hydrate (DBH) was prepared. The crystal structure confirmed that it belongs to triclinic, P-1 space group. The title compound includes one (C19H21O8)− anion, one (C9H11N2)+ cation and one water molecule, which assembled into a 2D-net framework by O–H···O and N–H···O hydrogen bonds. The quantum chemical computations using the B3LYP/6-311G (d, p) basis level of theory reveal that the optimized geometric structure is suitable to study the molecule. The theoretically simulated FT-IR spectra and electronic spectra of DBH are compared with experimental data. The results show that the B3LYP/6-311g (d, p) method fits well with the molecular structure. In addition, the thermodynamic properties have also been studied to determine the nature of the DBH.

Adsorption and corrosion inhibition characteristics of two medicinal molecules

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Hydrochloric Acid ◽  
Corrosion Rate ◽  
Mild Steel ◽  
Corrosion Inhibition ◽  
Half Life ◽  
Thermodynamic Data ◽  
Inhibition Efficiency ◽  
Gravimetric Method ◽  
Corrosive Environment ◽  
Corrosion Inhibition Efficiency

The corrosion inhibition characteristics of two medicinal molecules phenylalanine and rutin on mild steel in 1.0M Hydrochloric acid were evaluated using gravimetric method. Corrosion inhibition efficiency of 83.78 and 90.40 % was obtained respectively after seven days. However, phenylalanine showed weak accumulative higher corrosion inhibition efficiency. The presence of both molecules in the corrosive environment reduced the corrosion rate constant and increased the material half-life. Thermodynamic data calculated suggests a spontaneous adsorption of the molecules on the mild steel’s surface.

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

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