Thermodynamic Functions Of Adsorption Research Articles

NBis(2-hydroxyethyl) ammonium dodecanoate and its constituents as inhibitors for Al corrosion and H2 production in acid medium

2-(2-Hydroxyethylamino) ethanol (EA), dodecanoic acid (DA), and a freshly prepared ionic liquid named bis(2-hydroxyethyl) ammonium dodecanoate (ADD) were exercised as mitigators towards the corrosion of aluminum and the production of hydrogen in 2.0 M HCl. The study was performed by gravimetry, gasometry, potential-time measurements, and electrochemical methods. The examined concentration range of such inhibitors was varied between 5 × 10-6 M and 5 × 10-3 M. The amount of generated hydrogen is enhanced with temperature and lowered by increasing the concentration of the organic additive. Galvanostatic studies indicated that the utilized organic materials are effective inhibitors of a mixed type. The inhibition efficacy was found to increase with more additions of inhibitors and is lowered by temperature. ADD is the more effective inhibitor with a protective efficacy of 95.2% at 0.005 M and 298 K. The computed values of ΔGoads vary between – 35.48 and − 35.00 kJ/mol depending on the type of the organic compound and temperature that confirms the existence of a physical adsorption mechanism. The lowering in the Kads values with T confirms the escaping of several adsorbed organic particles from the contact metal interface. The thermodynamic adsorption functions, ΔG°ads, and Kads confirmed the spontaneous adsorption process, i.e., physical- and chemisorption mechanisms.

Studying the Thermodynamic Functions of adsorption of ion , Pb (II) on a new composite surface

A new type of compound was prepared in this study (AML). It was infrared spectroscopy. Use the composite to remove the Pb + 2 lead ion from its Aqueous solution by adsorption at certain conditions of the temperature and weight of theadsorbent material and the acidity and contact time. The composite was found to be effective in removing the lead ion at an acid function higher than 7 and at 25 ° C and contact time (90 min. The results showed that the adsorption on the surface was followed by Freundlich for adsorption. The thermodynamic functions (ΔS°,ΔH°,ΔG°) were calculated

The behavior of indium in dilute sodium tetraborate containing bromide ions in the presence of some ethoxylated surfactants

The potentiometric technique was used to study the oxide film repair and destruction on indium electrodes in 0.01 M Na2B4O7 containing various amounts of Br- ions. Higher amounts of Br- ions, ≥5 × 10−2 M, reduces the oxide film growth and initiate the destruction of oxide film by inducing pitting corrosion. The initiation of pitting corrosion is raised with the addition of more concentrations of Br- ions and raising the temperature. Some freshly prepared ethoxylated surfactant molecules, ETO I, ETO II, and ETO III were utilized as inhibitors to resist the oxide film destruction and sustain the oxide film repair with the formation of a layer of surfactant molecules. The protection efficacy of such molecules is found to rely on the concentration of the surfactant besides the number of ethylene oxide monomers per molecule. The inhibition efficacy reaches 87.8 %, 83.1 %, and 79.5 % with ETO III, ETO II, and ETO I, successively, at 0.01 M inhibitor concentration and 25 ºC. The inhibition mechanism relies on an adsorption process obeying Langmuir's model. The thermodynamic adsorption functions. Viz, Kads, and ∆G°ads are computed and explained. The inhibition efficacy of such compounds decreases in the order, ETO III> ETO II> ETO I.

Determination the Thermodynamic Functions of Adsorption of Some Food Coloring Dyes on the Surface of Leaves Grape Chemically Treated

Determination the Thermodynamic Functions of Adsorption of Some Food Coloring Dyes on the Surface of Leaves Grape Chemically Treated

Investigation of isotherms of differential heat-entropy adsorption of carbonyl sulfide in CaA zeolite during gas purification

The task of this research cycle was to measure adsorption isotherms (а) in the temperature range from 273 to 373 K, based on isotherms measured at different temperatures, to calculate isosteric heats (Qd) and entropies (∆Sd) of adsorption in order to select an effective adsorbent for purifying natural gas and oil products from sulfur-containing compounds. This article presents the results of studies of the isotherms of COS adsorption on CaA, carried out at four temperatures: 273, 298, 303, and 373 K, and the corresponding thermodynamic functions of adsorption in CaA zeolite.

Isotherms of differential heat and entropy adsorption of carbonyl sulfide in zeolite NaX when cleaning gases

The task of this research cycle was to measure adsorption isotherms (а) in the temperature range from 273 to 373 K, based on isotherms measured at different temperatures, to calculate isosteric heats (Qd) and entropies (∆Sd) of adsorption in order to select an effective adsorbent for purifying natural gas and oil products from sulfur-containing compounds. This article presents the results of studies of the isotherms of COS adsorption on NaX, carried out at four temperatures: 273, 298, 303, and 373 K, and the corresponding thermodynamic functions of adsorption in NaX zeolite.

Study of the thermodynamic functions of adsorption of hexachromic ion on a new superimposed surface

في هذه الدراسة تم تحضيرنوع جديد من المتراكبات ( الاتبلكات- ميلامين- يوريا ) AMU)) . تم تشخيص هذا المتراكب بواسطة مطيافية الاشعة تحت الحمراء . تم استخدام هذا المتراكب لازالة ايون الكروم السداسي Cr+6 من محلوله المائي باستخدام عملية الامتزاز تحت ظروف معينة من دالة حامضية ودرجة حرارة ووزن المادة المازة (المتراكب) وزمن تماس . وقد وجد ان المتراكب كان فعالاً في ازالة ايون الكروم عند دالة حامضية pH=2 وزمن تماس(90min) ودرجة حرارة (25 C°) وزن مادة مازة (2gm) . عين ايزوثيرم امتزاز ايون الكروم على السطح الماز باستخدام مطيافية الاشعة المرئية-فوق البنفسجية , واوضحت النتائج المستحصلة ان الامتزاز على السطح الماز يتبع معادلة فريندلش(Freundlich) للامتزاز . كما تم حساب الدوال الثرموديناميكية (∆Go ∆Ho , °( ∆S .

Adsorption Properties and Composition of Binary Kolliphor Mixtures at the Water-Air Interface at Different Temperatures.

The studies on the adsorption properties and composition of the adsorbed monolayer at the water–air interface of the binary Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) mixtures based on the measurements of the surface tension (γLV) of their aqueous solution in the temperature range from 293 to 318 K were carried out. The γLV isotherms were described by the exponential function of the second order and the Szyszkowski equation as well as predicted by Fainerman and Miller equation. The obtained γLV isotherms were analyzed using the exponential function of the second order, the Szyszkowski, Fainerman and Miller as well as independent adsorption equations. The γLV isotherms were also used for determination of the Gibbs surface excess concentration of RH40, ELP and their mixture (Γ) at the water–air interface as well as the mixed monolayer composition. Based on Γ and the constant a in the Szyszkowski equation, the standard thermodynamic functions of adsorption were considered. From the consideration dealing with the γLV isotherms obtained by us, it results, among others, that these isotherms for the non-ideal solution of macromolecular surfactants mixture can be predicted using the Fainerman and Miller equation. From this consideration, it also results that a simple method proposed by us, based on the isotherms of RH40 and ELP, allows us to predict the composition of their mixed monolayer in the whole concentration range of RH40 and ELP in the bulk phase.

Mimusops Elengi Leaves as Bioadsorbent for Removal of Uranyl Ion from Aqueous Solution

The removal of U(VI) ions from aqueous solutions with Bakul leaves was studied using a batch adsorption technique. The adsorption equilibrium, thermodynamics, and kinetic models were analyzed. The influence of pH, initial uranium concentration, contact time, temperature, and adsorbent dose on the uranium adsorption was estimated. The maximal uranium uptake was 86.4%. The U(VI) adsorption is well fitted using the Langmuir model and the pseudo-second-order model. Analysis of the thermodynamic functions of adsorption (ΔG°, ΔH°, ΔS°) at 303, 313 and 323 K shows that the adsorption on the surface of Bakul leaves is spontaneous and endothermic. Thus, Bakul leaves can be utilized as an economical, active, and eco-friendly adsorbent for uranium removal.

Physicochemical interpretation of the adsorption of 4-Bromophenol and 4-Chloroaniline on an activated carbon

Statistical physics theory was used to interpret the adsorption mechanism of 4-Chloroaniline and 4-Bromophenol on an activated carbon which was prepared from cashew nut shell. The adsorption of these organic molecules fits with a single-layer model assuming a single adsorption energy among five mechanisms explored. Experimental data were successfully analyzed via theoretical steric and energetic parameters that were associated to the adsorption mechanisms of tested pollutants. It was concluded that parallel, non-parallel and mixed orientations could be involved for the adsorption of these adsorbates on activated carbon. Calculated adsorption energies ranged from -16.3 to -14.3 kJ/mol for these two molecules, where a physisorption process occurred. Thermodynamic adsorption functions were also studied and discussed for the removal of these organic molecules with activated carbon. Overall, this paper attributed new insights about the adsorption mechanism of the tested adsorbates on activated carbon.

Methane Adsorption on Fе–BDC Metal–Organic Porous Structures at High Pressures

The isotherms of absolute methane adsorption in an Fe–BDC metal–organic porous structure after long-term storage were measured at a pressure as high as 40 MPa and the temperatures of 303, 313, 323, and 333 K. The dependences of differential molar isosteric heats of adsorption and entropies of adsorption on methane uptake were calculated. It was shown that taking into account the nonideality of a gaseous phase and steepness of the isotherm of adsorption leads to a temperature dependence of thermodynamic functions of adsorption. Both a sharp drop in the heat of adsorption and a local maximum of the entropy at the maximum values of methane uptake are indicative of rearranging the adsorbate structure and the probable formation of molecular methane associates in micropores.

Adsorption of New Azo Dyes Derived From 4-Aminoantipyrine from Aqueous solution by A New Type of Activated Carbon: Equilibrium and Kinetic Studies

This study is aimed to the synthesis of new azo dyes starting with 4-Aminoantipyrine. The thermodynamic behavior of the dyes adsorption on a new kind of activated carbon prepared from (Asphalt : Polymer) mixtures are studied. The research involved the selection of the optimum conditions for the adsorption process by studying the factors affecting it such as the effect of adsorbent dose, contact time, initial concentration and temperature, the work also included the fitting of two models of isotherm equations (Freundlich, Langmuir isotherms) on experimental data of adsorption models under consideration. This study was carried at different temperature and at range of concentrations. The constants of these isotherms were used to describe the nature of the studied systems and the type of interaction between dye and carbon surface. Depending on the results obtained from adsorption study at different temperature, the values of thermodynamic functions of adsorption were calculated at different concentration, using the equilibrium constant which obtained from the ratio between the concentration of the adsorbed and the free dye in solution. The above results showed that, the adsorption of these dyes are of physical nature and the experiential data were better obeyed Langmuir isotherm. The study also involved employing four kinetic models on the experimental data; pseudo first order, pseudo second order, Elovich and intraparticle diffusion equations. The results of this study showed that, the adsorption system under investigation obeyed the Pseudo second order model and the intraparticle diffusion is not the only mechanism controlling the adsorption systems under study.

Gas-chromatographic separation of enantiomers of 2-chlorobutane and 2-bromobutane on a cyanuric acid-modified Carboblack C adsorbent

The enantiomers of 2-chlorobutane and 2-bromobutane were separated by gas chromatography on a Carboblack C adsorbent modified by 10% cyanuric acid. Upon thorough mechanical stirring of a solution, cyanuric acid was shown to form chiral supramolecular structures on the surface of adsorbent particles analogously to the Kondepudi formation of chiral crystals of achiral molecules. The enantiomers of 2-bromobutane and 2-chlorobutane were found to undergo, respectively, complete and partial separation on the cyanuric acid-modified Carboblack C adsorbent. The separation of enantiomers is due to a high enantioselectivity of the modified adsorbent. The analysis of thermodynamic functions of adsorption showed that the differences in specific retention volumes of enantiomers are caused by the fact that one of enantiomers is adsorbed predominantly within the cavity of the supramolecular structure of cyanuric acid and another one is adsorbed on its surface. Separation on the proposed chiral stationary phase is characterized by the relative standard deviation of retention volumes no more than 7%.

Thermodynamics of krypton adsorption on microporous carbon adsorbent at high pressures

The behavior of the thermodynamic functions for the adsorption system krypton—microporous carbon sorbent ACC is described. The dependences of the differential molar isosteric heat of adsorption, entropy, enthalpy, heat capacity, and differential molar energy of the adsorption system on the adsorption equilibrium parameters were studied over the temperature range from 178 to 393 K and at pressures ranging from 1 to 6•106 Pa. Consideration of the non-ideality of gas phase and non-inertness of the adsorbent leads to a temperature dependence of the thermodynamic functions of the studied adsorption system, especially in the range of high pressures of the adsorptive. The non-ideality of the gas phase and the energetics of the adsorbent—adsorbate system exert the most significant effect on the thermodynamic functions. The non-inertness of the adsorbent in the investigated range of parameters of the adsorption system has a weak effect on the thermodynamic functions of adsorption. In the region of high filling of ACC micropores, the entropy increases, indicating the existence of processes, which change the structure of the adsorbate in the micropores, in particular, to form associates.

Porous polymer adsorbents modified with uracil

The possibility of using supramolecular uracil structures as surface modifiers of porous polymer adsorbents is studied. The properties of adsorbent samples obtained are found to depend on the amount of modifier applied and the specific surface of the original polymer. The formation of a net uracil structure, which affects thermodynamic adsorption functions of organic molecules, requires a higher surface concentration of the modifier than in the case of other supramolecular structures.

Inhibitive effects of 2-mercaptobenzimidazole (MBI) and 2-thiobenzylbenzimidazole (TBBI) on copper corrosion in 1 M nitric acid solution

The inhibitive actions of 2-mercaptobenzimidazole (MBI) and 2-thiobenzylbenzimidazole (TBBI) on copper corrosion in 1M HNO 3 medium were studied, using weight loss method, at 25 to 65°C and concentrations of 5.10 -5 M to 10 -3 M. The results showed that the two compounds had fairly good inhibiting properties for copper corrosion in the medium, with efficiencies of 90.0% for TBBI and 87.7% for MBI at 25°C and concentration of 10 -3 M. Modified Langmuir isotherm was found to provide an accurate description of the behavior of the two compounds. The thermodynamic functions of adsorption (ΔG° ads ,Q ads ) and the activation energy (E a ) were calculated. Negative values of changes in free energies were obtained, indicating the spontaneity of the adsorption process. From thermodynamic adsorption and dissolution functions, both physisorption and chemisorption were proposed. Quantum chemical parameters such as highest occupied molecular orbital energy (E HOMO ), lowest unoccupied molecular orbital energy (E LUMO ), energy gap (ΔE) and dipole moment (μ) were calculated for these compounds, using DFT/B3LYP/6-31G (d,p) method in order to discuss the correlation between theoretical data and experimental results. It was found that theoretical data support the experimental results. Key words: Corrosion Inhibitor, inhibition efficiency, adsorption isotherm, free adsorption energy, adsorption heat, theoretical calculation, dipole moment.

Inhibition of mild steel corrosion in hydrochloric acid solution by triazole derivatives: Part II: Time and temperature effects and thermodynamic treatments

The corrosion behaviour of mild steel in 0.1 M HCl solution without and with 5-amino-1,2,4-triazole (5-ATA), 5-amino-3-mercapto-1,2,4-triazole (5-AMT), 5-amino-3-methylthio-1,2,4-triazole (5-AMeTT) or 1-amino-3-methylthio-1,2,4-triazole (1-AMeTT) was studied as a function of the immersion time and the solution temperature. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used in this study. Results obtained showed that the inhibition efficiency (IE%) increases with increasing the immersion time reaching its maximum value after 1 h, IE% slightly decreased and subsisted at reasonable values at least during the studied 20 h. The adsorptive behaviour of the investigated inhibitors on the steel surface followed Langmiur-type isotherm. Increasing temperature was found to greatly enhance IE% till arriving plateau at about 80% for 5-ATA and more than 90% for the other compounds between 323 and 348 °K. The polarization and impedance measurements were in good agreement. These results indicate the suitability of the use of the investigated inhibitors in the cooling systems. The plots of ln K versus 1/ T for the four studied inhibitors showed non-linear behaviour. The standard enthalpy, Δ H ads o , entropy, Δ S ads o and free energy changes of adsorption Δ G ads o were evaluated using a proposed quadratic equation based on an inverse square dependence of the heat capacity on temperature. The calculated values of Δ G ads o were negative while those for Δ H ads o and Δ S ads o were positive. The values of the three thermodynamic functions of adsorption for the four investigated inhibitors were decreased with increasing the solution temperature. All the above results are suggestive of chemisorption of inhibitor molecules on the steel surface.

An inverse gas chromatographic study of the adsorption of alkanes on hydroxyapatite

Saturated alkanes adsorption on synthetic well-crystallized hydroxyapatite was studied by the inverse gas chromatography method, at zero coverage. Hydroxyapatite was prepared from Ca(OH)2 and H3PO4 aqueous solutions by a slow titration technique. The powder was characterized by XR diffraction, surface area measurement, and chemical analysis. Adsorption of saturated alkanes was investigated in the temperature range 338–353 K, using a flame ionization detector, and nitrogen as a carrier gas. The gas/solid partition coefficients were calculated from the retention data as well as the standard thermodynamic functions of adsorption, ΔH0d, ΔS0a and ΔG0a. Linear relationships between lnK and 1/T and between ΔG0a and the number of carbon atoms in saturated alkanes were observed. The dispersive component of the surface free energy was calculated for the investigated temperature region. A possible analytical application of hydroxyapatite to n-alkanes separation is given.

Multisolute adsorption equilibria in a reversed-phase liquid chromatography system

Multisolute adsorption equilibrium data are reported for benzyl alcohol, 2-phenylethanol and 2-methyl benzyl alcohol in a reversed-phase system. The adsorption data acquired exhibit very good thermodynamic consistency. The thermodynamic functions of adsorption were derived from the single-solute adsorption data measured at different temperatures. The values of the isosteric heats of adsorption suggest a nearly homogeneous surface for the adsorbent (octadecyl bonded silica) under consideration. A nonideal adsorbed solution theory model is applied to the experimental data. The model provides an excellent prediction of the multisolute adsorption equilibria based on the parameters derived from the single-solute adsorption data. Liquid–liquid equilibrium models were also used to describe the experimental data. In this case, the best representation of the experimental data is obtained when using 1-decanol to represent the stationary phase. Although the partition model provides a satisfactory representation of the experimental data at low concentrations, it fails to represent the curvature of the equilibrium data at higher concentrations of the solutes. The latter model is also unable to describe the temperature dependence exhibited by the single-solute adsorption data.

Structure Effect on Nonideal Mixing of Alkyl Methyl Sulfoxide and Alkyldimethylphosphine Oxide in Adsorbed Film and Micelle

The surface tension of aqueous solutions of the octylmethylsulfoxide (OMS)–decyldimethylphosphine oxide (DePO) and decylmethylsulfoxide (DeMS)–octyldimethylphosphine oxide (OPO) mixtures was measured as a function of the total molality of the surfactants and the composition in the surfactants. Compositions in the adsorbed film and micelle were thermodynamically evaluated from the total molality vs composition and the critical micelle concentration (CMC) vs compositon curves, respectively. The phase diagrams of adsorption and micelle formation were drawn and compared with those of the DeMS–DePO mixture previously studied. A large gap in composition was observed between the adsorbed film and the micelle coexisting at the CMC and ascribed to the differences in geometric structure between them and the constituent molecules. Negative deviation from ideal mixings in adsorbed film and micelle was observed for the OMS–DePO mixture, whereas a positive one was observed for the DeMS–OPO. The structure effect on the nonideal mixings was clarified by using the excess thermodynamic functions of adsorption and micelle formation calculated from the activity coefficients in the adsorbed film and micelle.