Proposing a new empirical adsorption isotherm known as Adejo-Ekwenchi isotherm
TL;DR: Adejo-Ekwenchi isotherm as mentioned in this paper is derived from the data obtained from our corrosion inhibition of mild steel in 2 M H2SO4 using three plant extracts using weight loss method studied at the temperature between 303 and 315 K.
Abstract: The derivation of an adsorption isotherm is, largely, by empirical deductions on which basis isotherms like the Langmuir, Freundlich, Temkin, Frumkin, Flory-Huggins, El-Awady, Dubinin-Radushkevich, etc. were developed. We hereby propose yet another two-parameter empirical adsorption isotherm known as Adejo-Ekwenchi isotherm, derived from the data obtained from our corrosion inhibition of mild steel in 2 M H2SO4 using three plant extracts using weight loss method studied at the temperature between 303 and 315 K. The isotherm is centred on the fact that, for any adsorption process, the amount of adsorbate uptake from bulk concentration is, always, inversely proportional to the difference between the total available surface on the adsorbent and the fraction that is covered by the adsorbate at a given temperature, prior to the attainment of maximum value of surface coverage. Therefore, at any time during the adsorption process, (1 - θ) is the available surface and this decreases with increase in concentration, and thus;
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21 Apr 2017
TL;DR: Extract of Corchorus olitorius stems (ECS) was used as a green inhibitor for the inhibition of mild steel corrosion in 0.5 M H2SO4 solution.
Abstract: Extract of Corchorus olitorius stems (ECS) was used as a green inhibitor for the inhibition of mild steel corrosion in 0.5 M H2SO4 solution. GC/MS was used for both qualitative and quantitative analysis of the extract. The corrosion performance of the extract was evaluated using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss. The results showed that ECS is a mixed-type inhibitor which reduces both anodic and cathodic reactions and the inhibition efficiency was reached up to 93%. Adsorption isotherm data was recorded at different temperatures and analyzed by selected adsorption isotherm models to reveal characteristics of inhibition. Thermodynamic calculations showed that the inhibition efficiency increases with increasing inhibitor concentration, and decreases with increasing temperature. Adsorption of ECS on the mild steel surface was found to be spontaneous and exothermic. Adsorption is suggested to be physisorption according to El-Awady isotherm model. Also, the scanning electron microscopy (SEM) was used to investigate the surface morphology to confirm the corrosion results.
29 citations
TL;DR: In this article, a cellulose nanocrystalline (CNC) was used for water purification from toxic pesticides such as difenoconazole, and two cellulose-based heterocycles were prepared by crosslinking with 2,6-pyridine dicarbonyl dichloride (Cell-X), and derivatizing with 2-furan carbonyl chloride (cell-D).
Abstract: The goal of this work was to develop polymer-based heterocycle for water purification from toxic pesticides such as difenoconazole. The polymer chosen for this purpose was cellulose nanocrystalline (CNC); two cellulose based heterocycles were prepared by crosslinking with 2,6-pyridine dicarbonyl dichloride (Cell-X), and derivatizing with 2-furan carbonyl chloride (Cell-D). The synthesized cellulose-based heterocycles were characterized by SEM, proton NMR, TGA and FT-IR spectroscopy. To optimize adsorption conditions, the effect of various variable such as time, adsorbent dose, pH, temperature, and difenoconazole initial concentration were evaluated. Results showed that, the maximum difenoconazole removal percentage was about 94.7%, and 96.6% for Cell-X and Cell-D, respectively. Kinetic and thermodynamic studies on the adsorption process showed that the adsorption of difenoconazole by the two polymers is a pseudo-second order and follows the Langmuir isotherm model. The obtained values of ∆G ° and ∆H suggest that the adsorption process is spontaneous at room temperature. The results showed that Cell-X could be a promising adsorbent on a commercial scale for difenoconazole. The several adsorption sites present in Cell-X in addition to the semi crown ether structure explains the high efficiency it has for difenoconazole, and could be used for other toxic pesticides. Monte Carlo (MC) and Molecular Dynamic (MD) simulation were performed on a model of Cell-X and difenoconazole, and the results showed strong interaction.
18 citations
TL;DR: The FTIR results confirmed that the dimethylpyrazole units have been immobilized onto the surface of the modified silica gel and the adsorption experiments were conducted for a wide range of solution pH, adsorbent dosage, temperature, initial concentration and contact time.
Abstract: Different pollutants from industries leach every day to soil and ground waters without treatment. The product N,N-bis (3,5-Dimethylpyrazol-1-yl methyl)-3-aminopropyl Polysiloxane (Si-C 3 H 6 NPz 2 ) was successfully prepared. The FTIR results confirmed that the dimethylpyrazole units have been immobilized onto the surface of the modified silica gel. The adsorption experiments were conducted for a wide range of solution pH, adsorbent dosage, temperature, initial concentration and contact time. It was observed that the percentage removal of methylene blue dye decreased with an increase initial concentration and temperature while it increased with increase in solution pH, contact time and adsorbent dose. Over 82% removal efficiency of methylene blue dye was achieved after 180 min at solution pH around 10, 20°C temperature, 0.25 g weight of dose and initial concentration of 15 mg/L of 50mL MB dye solution. Negative ∆G° values (-17.17 to -17.25 KJ/mol) indicate that the adsorption is favorable and spontaneous at these temperatures. The negative value of ∆H° (-16.66 KJ/mol) reflects an exothermic adsorption and indicates that the adsorption is favored at low temperature. The value of ∆H° was higher than those corresponding to physical adsorption. This would suggest that the adsorption process is chemical in nature. The small positive value of ∆S° (+1.78 J/mol.K) suggests that some structural changes occur on the adsorbent and the randomness at the solid/liquid interface in the adsorption system increases during the adsorption process. The results of the present study show that the prepared compound has a negative biological activity against Pseudomonas aeruginosa, Staphylococcus aurous, and Escherichia coli.
7 citations
TL;DR: In this paper, the effects of temperature, pH, contact time and adsorbent dosage on adsorption process of Cu(II), Zn (II), Mn(II) and Pb (II) ions were studied using standard solutions of their salts.
Abstract: This study was carried out to evaluate the efficiency of metal ions removal from aqueous solution using silica adsorbent. Silica was extracted from rice husk using sol-gel method. The silica was modified with 1.0 M of nitric acid. Using batch adsorption technique, the effects of temperature, pH, contact time and adsorbent dosage on adsorption process of Cu (II), Zn (II), Mn (II) and Pb (II) ions were studied using standard solutions of their salts. Percentage removal of the metals ions studied decreased as the temperature was varied between 28°C and 43°C. Percentage removal of metal ions studied showed an increase at different pH varying from 4 to 8 and decreased after the pH 8. The variation of contact time between 2 and 8 hours showed a sharp increase in metals removal from 2 to 6 hours but a slow increase after 6 hours. The percentage removal of metal ions increase as the adsorbent dosage increased between 0.5 g and 2.0 g. The maximum percentage removal of metal ions was found to be 99.48%. The general observed trend of efficiency being Cu>Pb>Zn>Mn. The experimental data was also tested using adsorption isotherm models of Langmuir and Freundlich and Langmuir model was found to be the best fit for the data.
7 citations
Cites background from "Proposing a new empirical adsorptio..."
...According to the Encyclopaedia Britannica (2013), adsorption is a capability of all solid substances to attract to their surfaces molecules of gaseous or solutions with which they are in contact [10]....
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01 Jan 2015
TL;DR: In this paper, the corrosion inhibition efficiency of a Cochlospermum tinctorium (CTE) on mild steel in 0.5M H2SO4 solution has been investigated using weight loss measurements, thermometric measurement and scanning electron microscopy studies.
Abstract: The corrosion inhibition efficiency of a Cochlospermum tinctorium (CTE) on mild steel in 0.5M H2SO4 solution has been investigated using weight loss measurements, thermometric measurement and scanning electron microscopy studies. The weight loss measurement indicates increase corrosion inhibition efficiencies that reach 97%. The weight loss and thermometric data established that the inhibition efficiency on mild steel increases with increase in the concentration of
7 citations
References
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TL;DR: In this article, the Sips equation was used to determine the best fit isotherm for each system, and six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error, and sum of absolute errors.
Abstract: The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three sets of experimental data overall.
1,187 citations
602 citations
TL;DR: In this paper, the inhibition of corrosion of aluminum in hydrochloric acid solutions by the ethanolic extract of the leaves of Ananas sativum was studied using weight loss and hydrogen evolution methods.
Abstract: The inhibition of corrosion of aluminum in hydrochloric acid solutions by the ethanolic extract of the leaves of Ananas sativum was studied using weight loss and hydrogen evolution methods. It was found that the plant extract retarded the acid induced corrosion of aluminum. Inhibition efficiency increased with increasing concentration of the extract and temperature. Adsorption studies revealed that Langmuir adsorption isotherm is the best adsorption model applicable to the adsorption of A. sativum on aluminum surface. Activation parameters such as activation energies (E a), activation enthalpy (ΔH o), and activation entropy (ΔS o) were evaluated from the effect of temperature on the corrosion and inhibition processes.
116 citations
"Proposing a new empirical adsorptio..." refers background in this paper
...Even many Authors observed that many adsorption processes which show clear chemical adsorption mechanism have their ΔGads values below -20 kJ/mol [13]....
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...Generally, it has been suggested that decrease in IE% (or surface coverage) with rise in temperature is indicative of physical adsorption mechanism, while increase in its value with rise in temperature signifies chemical adsorption mechanism [12, 13]....
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TL;DR: In this paper, the results indicate that all the extracts inhibited the corrosion process in the medium by virtue of adsorption and inhibition efficiency improved with the increase in concentration of concentration.
Abstract: Corrosion inhibition of aluminium alloy (AA3003) in 0.5 M HCl by extracts of selected plants was
investigated using gravimetric technique at 30 and 60°C. The studied plant materials include extracts
of Euphorbia hirta and Dialum guineense. The results indicate that all the extracts inhibited the
corrosion process in the medium by virtue of adsorption and inhibition efficiency improved with
concentration. Inhibition mechanisms were deduced from the temperature dependence of the
inhibition efficiency as well as from activation parameters that govern the process. Adsorption of both
plant extracts on the aluminium alloy was found to obey the Langmuir adsorption isotherm. The
phenomenon of physical adsorption is proposed from the obtained thermodynamic parameters.
Key words: Corrosion inhibition, aluminium alloy, acid solution, adsorption
55 citations
"Proposing a new empirical adsorptio..." refers result in this paper
...As can be seen from the Table the new isotherm gives values which correlate very well with those obtained through the conventional method and other well-known adsorption isotherms [16, 17], giving credence to the formulation of yet another two-parameter adsorption isotherm....
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TL;DR: In this paper, seven quaternary ammonium bromides of different heterocyclic compounds were investigated as corrosion inhibitors of mild steel in 1M HCl using gravimetric and polarisation techniques.
42 citations