Adsorption of ibuprofen on organo-sepiolite and on zeolite/sepiolite heterostructure: Synthesis, characterization and statistical physics modeling

A synthesized zeolite/sepiolite nanoheterostructure (Zeo-Sep) and a modified organo-sepiolite (O-Sep) have been employed as clay-based adsorbents to study the adsorption mechanism of ibuprofen (IBP) from aqueous solution. New equilibrium data of IBP adsorption were determined at 20–60 °C, which were utilized to perform a theoretical analysis of the removal mechanism using statistical physics models. To interpret the IBP adsorption mechanism at molecular level, three advanced statistical physics models were employed. Modeling results indicated that IBP adsorption on Zeo-Sep and O-Sep was associated to the formation of two layers. It has been deduced that the IBP adsorption occurred by horizontal and non-horizontal orientations on both adsorbents depending on the temperature thus reflecting that the adsorption was a multi-docking and multi-molecular process, respectively. At high temperature (i.e., 60 °C), it was found that the number of captured IBP molecules is around two reflecting that the IBP was aggregated (i.e., formation of a dimer) in solution. IBP adsorption capacity at saturation was higher on O-Sep than that of Zeo-Sep at all tested temperatures indicating that the O-Sep adsorbent was more suitable for the removal of this pharmaceutical. The interactions between IBP and both adsorbents (IBP/O-Sep, and IBP/Zeo-Sep) and between IBP molecules (IBP- IBP) have been calculated to further characterize the adsorption mechanism, which was found to be a physisorption process. These new findings provided microscopic explanations regarding the IBP adsorption mechanism using clay-based adsorbent

Theoretical study and analysis of o-nitrophenol adsorption using layered double hydroxides containing ca-al, ni-al and zn-al

A theoretical assessment of the o-nitrophenol adsorption on layered double hydroxides containing different metallic species (Ca-Al, Ni-Al and Zn-Al) was performed. Experimental o-nitrophenol adsorption isotherms obtained at different adsorption temperatures with these layered double hydroxides were analyzed using a statistical physics monolayer model. Model calculations showed that the o-nitrophenol aggregation could occur with a high degree. It was estimated that the o-nitrophenol adsorption implied a non-flat orientation on all adsorbent surfaces and this process was multi-molecular. It was also demonstrated that there was no significant difference on the o-nitrophenol adsorption capacities of tested adsorbents, which varied from 77 to 135, 95 to 122 and 74 and 130 mg/g for Ca-Al, Ni-Al and Zn-Al layered double hydroxides, respectively. This finding suggested that the incorporation of Ca-Al, Ni-Al and Zn-Al in the layered double hydroxide structure played a similar role to adsorb o-nitrophenol molecules from aqueous solution. Calculated adsorption energies and thermodynamic functions confirmed an exothermic adsorption with the presence of physical-based interaction forces. This paper highlights the importance of reliable theoretical calculations based on statistical physics theory to contribute in the understanding of the adsorption mechanisms of a relevant water pollutant using layered double hydroxides as promising adsorbents for industrial applications

Trapping of Ag+, Cu2+, and Co2+ by faujasite zeolite Y: new interpretations of the adsorption mechanism via DFT and statistical modeling investigation

This work evaluated the potential of a synthesized faujasite-type zeolite Y as an adsorbent for the removal of relevant heavy metals such as silver (Ag+), copper (Cu2+), and cobalt (Co2+). The adsorption data of Ag+, Cu2+, and Co2+ ions were determined experimentally at pH 6 and temperatures of 298, 308, and 318 K. Two theoretical approaches have been applied based on statistical physics modeling and density functional theory (DFT) to understand and characterize the ion exchanges involved in the removal of all metals. Results showed that this zeolite was more efficient for the adsorption of Ag+ via cation-exchange. Based on the physical modelling, the removal of heavy metals on this zeolite was mono and multi-ionic (simple and multi-interactions), where the ions interacted via one and two adsorption sites. It was also noted that the temperature increment generated more available functional groups of the zeolite, facilitating the access to the smaller cavities and the interactions with the adsorbent. Adsorption energies for removing these metals with tested zeolite were slightly endothermic and were consistent with the typical values reported for ion exchange systems of heavy metals + zeolites. DFT results demonstrated that these cationic exchange energies depend on the nature of precursor salt, but with the same ranking. Both statistical and DFT approaches agreed that exchange Ag+ in zeolite Y was easier than Cu2+ and Co2+. Overall, the application of both theoretical approaches provided a reliable interpretation of the adsorption mechanism

Implementation of a multilayer statistical physics model to interpret the adsorption of food dyes on a chitosan film

This paper reports the application of an advanced multilayer model to study the adsorption of food dyes FD&C blue No. 2, acid red 18, FD&C red No. 2, and FD&C yellow 5 from aqueous solutions with a chitosan film. These dyes' adsorption mechanisms were discussed and analyzed at 298–328 K and pH 4–7 via statistical physics calculations. Physicochemical parameters were utilized to explain the dye adsorption at the molecular scale. Modeling results showed dye aggregation phenomena where each functional group of chitosan film adsorbed several dye molecules simultaneously at different tested temperatures. Aqueous solution temperature reduced the dye adsorption capacities, attributed to the exothermic nature of dye removal. The chitosan film was more effective for the adsorption of dye FD&C yellow 5. The estimated adsorption energies for dye-chitosan film and dye-dye interactions confirmed an exothermic physisorption associated with van der Waals forces and hydrogen bonding. This study's results contributed to expanding the knowledge on the adsorption mechanisms of dye molecules using biopolymers like chitosan

Adsorption of dyes brilliant blue, sunset yellow and tartrazine from aqueous solution on chitosan: Analytical interpretation via multilayer statistical physics model

This study reports the statistical physics modeling of the adsorption of three dyes brilliant blue (BB), sunset yellow (SY) and tartrazine (TT) on chitosan from aqueous solution. A multilayer statistical physics model was applied to understand the dye adsorption at different temperatures (i.e., 298–328 K) and pH 3. Modeling results showed that the adsorption was performed with a horizontal position of BB, SY, and TT molecules on the chitosan surface. Dye adsorption capacities ranged from 406.19 to 814.27 mg/g for BB, from 924.88 to 1432.98 mg/g for SY and from 611.27 to 1065.55 mg/g for TT, respectively. Overall, the chitosan showed the highest adsorption capacities for dye SY (Q0 (SY-chitosan) > Q0 (TT- chitosan) > Q0 (BB- chitosan)). The analysis of adsorption energies indicated that the removal of these dyes was an exothermic physisorption process, which could be governed by steric parameters according to the results obtained with the multilayer statistical physics model. This study contributes with new theoretical and experimental findings of the dye adsorption using natural polymers

New Interpretations of the Adsorption Process of Tetracycline on Biochar via Experimental and Theoretical Studies

A theoretical interpretation of the adsorption mechanism of tetracycline (TCCN) on biochar either in raw form (ADS1) or modified by chitosan-Fe/S (ADS2) is reported in the paper. An interpretative model is applied to the adsorption dataset, and considers that the adsorption of TCCN occurs with the formation of two layers on the investigated adsorbent. The theoretical model allows good data interpretation, confirming that TCCN adsorption capacity increases with temperature. The adsorption capacity at saturation (ACS) of TCCN on the ADS1 varied from 61.91 to 91.01 mg/g. while for ADS2 it varied from 135.76 to 202.50 mg/g. This difference is probably related to the difference in adsorbent properties and to the beneficial effect exerted by the adsorbent modification. Modeling results show also that TCCN is removed via a non-parallel orientation on both ADS1 and ADS2. For a thorough analysis of this mechanism, all adsorption energies (TCCN-ADS1, ADS2, and TCCN-TCCN) are determined at different temperatures

Synergistic Adsorption of Pb2+ and CrO42- on an Engineered Biochar Highlighted by Statistical Physical Modeling

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Understanding the Adsorption Mechanism of Ag+ and Hg2+ on Functionalized Layered Double Hydroxide via Statistical Physics Modeling

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