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Journal ArticleDOI: 10.1016/J.CHEMOSPHERE.2021.130176

Statistical analysis of adsorption isotherm models and its appropriate selection

04 Mar 2021-Chemosphere (Pergamon)-Vol. 276, pp 130176-130176
Abstract: In adsorption research, there was a good amount of adsorption data on various absorbent-adsorbate systems and many isotherm models were studied but there was no study on applicability of models to a group of adsorbent-adsorbate systems. In order to establish this, adsorption data obtained from literature for activated carbon with different solutes/sorbate(s) were considered and modelled with various adsorption models. The molecular mass of the solutes varies from 78.118(Benzene) to 932(Direct blue 2B dye) g.mol−1 and adsorbent surface area varies from 516 to 1100 m2 g−1. In this work, twelve commonly known isotherms models were employed to correlate the adsorption data. For modelling polymath® software has been used. The input data for the polymath® software were amount of adsorbate per unit amount of adsorbent, qe vs. concentration, ce. Nonlinear optimization of isotherm data gives model parameters. The correlating ability of the various models was compared in terms of arithmetic average relative deviation (AARD) calculated based on qe. The lowest overall AARD% values were observed for Baudu Isotherm and Langmuir-Freundlich and the corresponding AARD% values were 2.6 and 2.8 respectively. The highest overall AARD% value was observed for Marczewski-jaroniec isotherm and the corresponding AARD% is 23.5. Corrected Akaike’s information criterion (AICcorrected) was employed to known the best model. We observed lowest AICcorrected(15.859) value for Langmuir-Freundlich isotherm and the highest AICcorrected(59.283) value for Marczewski-jaroniec isotherm. AICcorrected reveals that Langmuir-Freundlich isotherm was efficient in correlating the isotherm data. Further, Pair-t test was performed between Baudu isotherm and other model.

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Topics: Adsorption (51%)
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12 results found


Journal ArticleDOI: 10.1016/J.ENVRES.2021.111146
Abstract: In this study adsorption of Cd(II) ions using the pyrolysis assisted Palmyra palm male inflorescence (PAPMI) was systematically examined. A batch adsorption study was carried out to determine the type of interactions and removal efficiency which is based on the surface property of PAPMI. The diverse parameters which affect the adsorption performance of PAPMI for Cd(II) ion removal were optimized: biosorbent dose – 1.25 g/L, pH – 6.0, temperature – 303 K, initial cadmium ions concentration – 50 mg/L and contact time – 40 min. Pseudo-first order kinetics and Langmuir isotherm models were more suitable to describe the adsorption kinetics and isotherm, respectively. Therefore, modeling studies portrayed the present Cd(II) ions adsorption on PAPMI as monolayer adsorption occurs on the homogeneous surface and follows the physisorption mechanism. The maximum adsorption capacity of the synthesized PAPMI was examined as 233.2 mg/g from the equilibrium isotherm investigation. Based on the calculated thermodynamic parameters (ΔGo, ΔHo and ΔSo) values, the present Cd(II) ions adsorption on PAPMI was explicated as feasible, and exothermic. The outcome proposed that Palmyra palm male inflorescence can be a suitable adsorbent for expulsion of Cd(II) ions from aqueous environment. In the interim, the utilization of pyrolysis assisted is a viable and fast uptake innovation for the removal of heavy metals from water environment.

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Topics: Adsorption (61%), Langmuir adsorption model (56%), Water environment (54%) ... read more

6 Citations


Journal ArticleDOI: 10.1016/J.MOLLIQ.2021.116670
Abstract: The zeolitic imidazole framework-8 (ZIF-8) was prepared in this study, which is a form of metal organic framework (MOF). ZIF-8 was characterized using powder X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Brunauer-Emmett-Teller surface area (BET), scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX). The material was used to eliminate Remazol Black 5 (RB5) and Brilliant Green (BG) dyes from aqueous media via chemical adsorption process. Adsorption kinetics, isotherms, dosage effect, initial concentration effect and pH were all investigated. According to the findings of the previous studies, the pseudo-second-order kinetics model and the Langmuir isotherm match our experimental adsorption data. Thermodynamic adsorption characteristics such as enthalpy, entropy, and Gibb's free energy were calculated. The sorption process was taking place spontaneously and it was endothermic in nature with high disorder of solid–liquid interface. ZIF-8′s AC and DC properties were investigated, and it revealed typical semiconductor activity.

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Topics: Adsorption (61%), Zeolitic imidazolate framework (58%), Langmuir adsorption model (55%) ... read more

4 Citations


Journal ArticleDOI: 10.1016/J.JENVMAN.2021.113052
Abstract: Acid mine drainage (AMD) with toxic arsenic (As) is commonly generated from the tailings storage facilities (TSFs) of sulfide mines due to the presence of As-bearing sulfide minerals (e.g., arsenopyrite, realgar, orpiment, etc.). To suppress As contamination to the nearby environments, As immobilization by Ca–Fe–AsO4 compounds is considered one of the most promising techniques; however, this technique is only applicable when As concentration is high enough (>1 g/L). To immobilize As from wastewater with low As concentration (~10 mg/L), this study investigated a two-step process consisting of concentration of dilute As solution by sorption/desorption using schwertmannite (Fe8O8(OH)8–2x(SO4)x; where (1 ≤ x ≤ 1.75)) and formation of Ca–Fe–AsO4 compounds. Arsenic sorption tests indicated that As(V) was well adsorbed onto schwertmannite at pH 3 (Qmax = 116.3 mg/g), but its sorption was limited at pH 13 (Qmax = 16.1 mg/g). A dilute As solution (~11.2 mg/L As) could be concentrated by sorption with large volume of dilute As solution at pH 3 followed by desorption with small volume of eluent of which pH was 13. The formation of Ca–Fe–AsO4 compounds from As concentrate solution (2 g/L As(V)) was strongly affected by temperature and pH. At low temperature (25–50 °C), amorphous ferric arsenate was formed, while at high temperature (95 °C), yukonite (Ca2Fe3–5(AsO4)3(OH)4–10·xH2O; where x = 2–11) and johnbaumite (Ca5(AsO4)3OH) were formed at pH 8 and 12, respectively. Among the synthesized products, johnbaumite showed strongest As retention ability even under acidic (pH 9) conditions.

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Topics: Schwertmannite (58%), Sorption (57%), Arsenic (56%) ... read more

2 Citations


Open accessJournal ArticleDOI: 10.3390/SEPARATIONS8080107
24 Jul 2021-Separations
Abstract: Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties is of great significance. In this study, various methods including flotation tests, contact angle measurements, batch adsorption tests and Density Functional Theory (DFT) simulations were carried out to understand the adsorption characteristics and mechanism. Results of the contact angle measurements showed that the inhibition effects of calcium ions on molybdenite flotation kinetics were mostly attributed to the decrease of the edge surface hydrophobicity, as the contact angle of the edge surface decreased more than the face surface after treatment with calcium ions. While fitting the results of batch adsorption tests with adsorption kinetics and isotherm models, it was found that the Lagergen pseudo-first-order equation and the Freundlich isotherm model nicely follow the experimental trend. Moreover, DFT calculation results indicated that both Ca2+ and CaOH+ preferentially adsorb on the molybdenite (100) surface, particularly the edge surface, which was consistent with the contact angle results. Ca2+ adsorbed on the Mo-top site on the S-(100) surface by forming Ca-S bonds, transferring electrons from Ca 3d orbitals to S 3p orbitals. CaOH+ adsorbed on the S-top site of Mo-(100) surface by forming a strong covalent Mo-O bond and S-Ca bond. The results provide a basis for understanding and improving the separation effect of molybdenite from other minerals in the presence of calcium ions.

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Topics: Molybdenite (57%), Adsorption (56%), Freundlich equation (55%) ... read more

1 Citations


Open accessJournal ArticleDOI: 10.3390/IJERPH18094489
Abstract: In this paper, we describe the removal of cephalosporin C (CPC) from aqueous solutions by adsorption onto activated olive stones (AOS) in a stirred tank. For comparative purposes, several experiments of adsorption onto commercial granular activated carbon were carried out. A quantum study of the different species of cephalosporin C that, depending on the pH, exist in aqueous solution pointed to a favorable mass transfer process during adsorption. Activated olive stones were characterized by SEM, EDX and IR techniques and their pHzc was determined. A 10-3 M HCl cephalosporin C solution has been selected for the adsorption experiments because at the pH of that solution both electrostatic and hydrogen bond interactions are expected to be established between the adsorbate and the adsorbent. The adsorption process is best described by the Freundlich isotherm model and the pseudo-second-order kinetic model, while the adsorption mechanism is mainly controlled by film diffusion. Under the conditions studied, the adsorption process is of a physical nature, endothermic and spontaneous. Comparison of the adsorption results obtained in this paper with those of other authors shows that the efficiency of AOS is 20% of that of activated carbon but 65% higher than that of the XAD-2 adsorbent. Considering its low price, abundance, easy accessibility and eco-compatibility, the use of activated olive stones as adsorbents for the removal of emerging pollutants from aqueous solutions represents an interesting possibility from both the economic and the environmental points of view.

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Topics: Freundlich equation (63%), Adsorption (62%), Activated carbon (58%) ... read more

1 Citations


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43 results found



Open accessJournal ArticleDOI: 10.1021/JA02242A004
Abstract: solutions investigated, the absorption index diminishing approximately 1% for a rise in temperature of one degree. 6. In liquid ammonia rough measurements of concentration showed the absorption index to be proportional to the total concentration of metal. 7. In methylamine the absorption index, at the wave length of the band maximum is also proportional to the total concentration of metal. At shorter wave lengths, however, deviations were observed, the absorption increasing more rapidly with concentration than Beers’ law would demand. The ratio of the absorption index a t 650pp to that a t 53opp increases not only with increasing concentration of the metal but also with increasing concentration of the reaction product of the metal with methylamine, and probably also with increasing temperature. 8. These observations can be accounted for by the following hypotheses: The color in all cases is due to electrons combined with the solvent. In ammonia the dissociation of the metal into electrons is nearly complete, and the concentration of electrons uncombine4 with solvent is negligible compared with that of the solvated electrons. In other words, the solvation of the electrons is nearly complete. In methylamine, on the other hand, the concentration of un-ionized metal is no longer negligible and is responsible for the increased absorption a t the shorter wave lengths. The solvation of the electrons in methylamine is incomplete and diminishes as the temperature is increased.

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Topics: Platinum (54%), Mica (53%), Plane (geometry) (50%) ... read more

16,125 Citations


Book ChapterDOI: 10.1007/978-1-4612-1694-0_15
01 Jan 1973-
Abstract: In this paper it is shown that the classical maximum likelihood principle can be considered to be a method of asymptotic realization of an optimum estimate with respect to a very general information theoretic criterion. This observation shows an extension of the principle to provide answers to many practical problems of statistical model fitting.

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Topics: Likelihood principle (64%), Likelihood function (59%), Bayesian information criterion (58%) ... read more

15,032 Citations


Open accessBook
01 Jan 1960-
Abstract: Capillarity. The Nature and Thermodynamics of Liquid Interfaces. Surface Films on Liquid Substrates. Electrical Aspects of Surface Chemistry. Long--Range Forces. Surfaces of Solids. Surfaces of Solids: Microscopy and Spectroscopy. The Formation of a New Phase--Nucleation and Crystal Growth. The Solid--Liquid Interface--Contact Angle. The Solid--Liquid Interface--Adsorption from Solution. Frication, Lubrication, and Adhesion. Wetting, Flotation, and Detergency. Emulsions, Foams, and Aerosols. Macromolecular Surface Films, Charged Films, and Langmuir--Blodgett Layers. The Solid--Gas Interface--General Considerations. Adsorption of Gases and Vapors on Solids. Chemisorption and Catalysis. Index.

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Topics: Wetting (57%), Adsorption (54%), Chemisorption (52%)

10,786 Citations


Journal ArticleDOI: 10.1177/0049124104268644
Abstract: The model selection literature has been generally poor at reflecting the deep foundations of the Akaike information criterion (AIC) and at making appropriate comparisons to the Bayesian information...

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7,541 Citations