Entropy Of Adsorption Research Articles

Effect of tabebuia heterophylla plant leaves extract on corrosion protection of low carbon steel in 1M HCl medium: Electrochemical, quantum chemical and surface characterization studies.

In the current study the chemical constituents of Tabebuia heterophylla plant leaves extract (THLE) evaluated as corrosion inhibitor for low carbon steel (LCS) in 1 M HCl. The major component present in plant extract was Hexadecanoic acid 2-hydroxy-1-(hydroxymethyl) ethyl ester confirmed by Gas Chromatography with Mass spectroscopic (GC-MS) analysis. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation (PDP) and weight loss measurements were used to evaluate the THLE ability to protect low-carbon steel surface against corrosion in 1M HCl medium. The maximum inhibition efficiency reported as 95.45%, 93.99% and 94.79% by weight loss measurements, EIS and PDP methods respectively. In the prolongation of the work, the entropy of adsorption (Δ Sa*), enthalpy of adsorption (Δ Ha*), Gibbs free energy of adsorption (Δ Ga*), and activation energy (Ea) of the reaction were calculated. In absence of inhibitor, the Ea value was found to be minimum 49.38 kJ/mol whereas for optimum concentration of THLE it was found to be 77.2 kJ/mol implies more energy is required to undergo corrosion. The surface morphological observation from Scanning Electron Microscope (SEM), Atomic Force Microscopic (AFM) and Contact angle explored the effective adsorption of THLE. AFM values revealed that average surface roughness (Ra) value of LCS is high (188.08), where as in the presence of THLE, Ra values significantly reduced to minimum value of 37.226. Further chemical interactions between THLE and the low-carbon steel surface as well as inhibitory mechanism were further elucidated by theoretical simulations such as Density Functional Theory (DFT) calculations and Molecular dynamics (MD) simulations.

Effects of maltodextrin on water adsorption and thermodynamic properties of Codonopsis Radix spray-dried powder

This study aims to reveal the effects of maltodextrin(MD) on the water adsorption and thermodynamic properties of Codonopsis Radix(DS) spray-dried powder by determining the moisture and energy changes of the powder in the process of moisture absorption. The static weighing method was used to obtain the isothermal water adsorption data of the spray-dried powder in 6 saturated salt solutions(KAc, MgCl_2·6H_2O, K_2CO_3, NaBr, NaCl, and KCl) at 3 temperatures(25, 35, and 45 ℃). Six models were used for fitting of the water adsorption process, and the most suitable model was selected based on the model performance. Furthermore, the corresponding net equivalent adsorption heat and differential entropy were calculated, and the adsorption entropy change was integrated. The linear relationship between net equivalent adsorption heat and differential entropy was drawn based on the entropy-enthalpy complementarity theory. The results showed that the water adsorption properties of DS and DS-MD spray-dried powder followed the type Ⅲ isotherm and was well fitted by the GAB model. The monolayer water content M_0 decreased with the increase in temperature. At the same temperature, the M_0 of DS spray-dried powder decreased after the addition of MD. The net equivalent adsorption heat and differential entropy of DS and DS-MD spray-dried powder decreased with the increase in water content, which presented a linear relationship. The addition of MD decreased the water activity corresponding to the lowest integral adsorption entropy of the powder, and the system became more stable. The results indicated that the spray-dried powder became more stable after the addition of MD.

New Progress on London Dispersive Energy, Polar Surface Interactions, and Lewis's Acid-Base Properties of Solid Surfaces.

The determination of the polar surface free energy, polar properties, and Lewis's acid base of solid materials is of capital importance in many industrial processes, such as adhesion, coatings, two-dimensional films, and adsorption phenomena. (1) Background: The physicochemical properties of many solid particles were characterized during the last forty years by using the retention time of injected well-known molecules into chromatographic columns containing the solid substrates to be characterized. The obtained net retention time of the solvents adsorbed on the solid, allowing the determination of the net retention volume directly correlated to the specific surface variables, dispersive, polar, and acid-base properties. (2) Methods: Many chromatographic methods were used to quantify the values of the different specific surface variables of the solids. However, one found a large deviation between the different results. In this paper, one proposed a new method based on the London dispersion equation that allowed the quantification of the polar free energy of adsorption, as well as the Lewis's acid-base constants of many solid surfaces. (3) Results: The newly applied method allowed us to obtain the polar enthalpy and entropy of adsorption of polar model organic molecules on several solid substrates, such as silica, alumina, MgO, ZnO, Zn, TiO2, and carbon fibers. (4) Conclusions: our new method based on the separation between the dispersive and polar free surface energy allowed us to better characterize the solid materials.

Synthesis and characterization of the magnetic chitosan/zinc oxide nanocomposite: an efficient magnetic adsorbent for removal of harmful aromatic micropollutants from wastewater

In this work, a magnetic chitosan/zinc oxide nanocomposite (CS/ZnO-Fe3O4) was fabricated for efficient adsorptive removal of harmful aromatic micropollutants, including Cephalexin (CFX) antibiotic and Eosin B (EB) dye from wastewater samples. To maximize the adsorption efficiency of the CS/ZnO-Fe3O4, the adsorption process was first modeled and statistically optimized by using the response surface methodology based on central composite design (RSM-CCD). The results demonstrated that the maximum removal efficiency of the adsorbent for CFX and EB was 98.87% and 99.08%, respectively. Also, the adsorption isotherms, kinetics, and thermodynamics were also studied in detail under the optimum conditions. The results indicated that the adsorption equilibrium data was fit well with the Langmuir isotherm model, which indicated monolayer adsorption via chemisorption process. The Langmuir maximum adsorption capacity (Qmax) was 81.38 mg g−1 and 144.4 mg g−1 for CFX and EB, respectively. The adsorption kinetic was followed by the pseudo-second-order kinetic model, and the thermodynamic studies showed that the adsorption process was endothermic and spontaneous, as well as that adsorption entropy was also increased during the process. Also, the main adsorption mechanism was considered to be based on H-bonding, n-π, and electrostatic interactions. The regeneration experiments indicated that the spent adsorbent was easily regenerated by NaOH solution (0.1 mol L−1) and reused for subsequent cycles without a significant decrease in its performance, so that removal efficiency remained about 90% at the fourth cycle. Overall, the results indicated that CS/ZnO-Fe3O4 could be used as a promising adsorbent for the efficient removal of aromatic micropollutants from wastewater.

Entropy driven separation of xylene isomers on graphitic carbon adsorbents

Separation of xylene isomers remains one of the most important and challenging applications of adsorption-based separations in petrochemical industry. Despite the sustainable success of zeolite-based separations a search for efficient adsorbents selective for xylenes, especially para-xylene, is constantly ongoing. In this work, a potentially scalable chromatographic separation of all three xylenes was achieved on graphitic carbon sorbents, including a self-packed sorbent based on an oligo-graphene. A curious feature of this separation is stronger retention of para-xylene than meta- and, in some conditions, even than ortho-xylene. Noticeably, separation selectivity between para- and meta-isomers does not depend on temperature. Apparently, lower entropy of para-xylene in solution due to its higher molecular symmetry leads to a lesser adsorption entropy loss, which makes its adsorption statistically more likely. The concept of using carbon adsorbents for entropy driven chromatography separations may be useful for the isolation of xylenes from their mixture and, possibly, for other positional isomers separation.

Differential entropy and thermokinetics of ammonia molecule adsorption on CaA zeolite (M-22)

Differential entropy and thermokinetics of ammonia molecule adsorption on CaA zeolite (M-22)

Direct measurement of the hydrogen adsorption entropy on shape-controlled Pt nanoparticles using electrochemical microcalorimetry

We measured the entropy of hydrogen adsorbed on Pt NPs with 3 different shapes. The entropy depends on the local geometry of the particles and matches the entropy of hydrogen adsorbed on single crystals with the corresponding orientation.

Molecular Simulation of Thermodynamic Properties of CH4/CO2 Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions.

In order to further elucidate the thermodynamic mechanism of CH4/CO2 adsorption by coal molecules, the adsorption behavior of a molecular model of coal (C206H128O36N2) at Wucaiwan, Zhundong was investigated by applying Materials Studio 2020 and Monte Carlo (GCMC) simulation methods, and the adsorption behavior of CH4 and CO2 was studied from the thermodynamic point of view under the conditions of different temperatures, pressures, and moisture contents. The results showed that at different temperatures or moisture contents, CH4 molecules had a low-density scattering distribution and CO2 molecules had a high-density polymerization distribution. Temperature and moisture content and adsorption constants a and b were negatively correlated. Under the same conditions, the relationship between single- and binary-component adsorption amounts was CO2 > CH4 and the relationship between heat of adsorption was CO2 > CH4. When adsorption potential energy or entropy of adsorption was the same, the adsorption capacity was CO2 > CH4. Temperatures and moisture contents were negatively correlated with the total adsorption capacity of CH4/CO2; pressure was positively correlated with the total adsorption capacity of CH4/CO2. The effect of temperature on the equivalent heat of adsorption was greater than that of pressure at different temperatures, and the entropy of adsorption was positively correlated between temperature and CH4/CO2, while the amount of adsorption was negatively correlated with the entropy of adsorption. The effect of moisture content on the equivalent heat of adsorption was greater than that of pressure at different moisture contents, and the entropy of adsorption was negatively correlated between moisture content and amount of adsorption. The adsorption entropy of CH4/CO2 was negatively correlated, and the adsorption amount was positively correlated to the adsorption entropy. At a temperature above 318 K or moisture content above 10%, the total CH4/CO2 adsorption decreased significantly and the CO2 adsorption decreased significantly. From a thermodynamic point of view, the presence of a large amount of H2O had a much greater effect on CO2 than on CH4, and an increase in temperature or moisture content was unfavorable for CO2 sequestration, CO2 stripping of CH4, and control of CH4 diffusion and desorption, whereas at low temperature, high pressure, and moisture content <1%, the effect of stripping, sequestration, and control was good.

Diclofenac sodium drug adsorption isotherm on carbon xerogels via an advanced two layers model with two energies

In this work, four carbon xerogels (XCs) adsorbents, which were prepared by the polymerization of formaldehyde (F) and resorcinol (R) using cesium carbonate (Cs) as catalyst at 4 M ratios R/Cs = XCs-100, XCs-500, XCs-1000 and XCs-2000, were utilized to interpret and understand the adsorption mechanism at a molecular level of non steroidal anti inflammatory drug (NSAID), namely diclofenac sodium (DCF). Hence, Four adsorption isotherms were utilized to present the evolution of the adsorbed quantity (Qa) as a function of drug concentration describing the DCF adsorption on the four carbons xerogels at T = 298 K and at pH = 7. In addition, two other adsorption systems, describing the adsorption of DCF on XCs-500, were plotted by varying two experimental conditions: temperature and solution pH. All these experimental data were adjusted and analyzed via the advanced two layers model with two adsorption energies (A2LM2E), which was chosen as the most adequate statistical physics model. Furthermore, stereographic and energetic parameters of A2LM2E namely: the number of DCF molecules per XCs sites (n), the adsorbed quantity at saturation (Qas) and the concentrations at half saturation (C1 and C2) were estimated by a multi-variable non-linear regression. The fitting results indicated that the DCF drug molecules were docked with mixed and non-parallel orientations on the different XCs adsorbents. The investigation of the adsorbed quantity at saturation indicated that Qas increased as follows: Qas (XCs-2000) < Qas (XCs-100) < Qas (XCs-1000) < Qas (XCs-500), showing that the XCs-500 was more efficient for the adsorption of DCF drug than the other adsorbents. The calculated molar adsorption energies ΔE1 and ΔE2 for the studied adsorption systems affirmed the exothermic and the physical characters of the adsorption mechanism since ΔE1 and ΔE2 values were positive and inferior to 40 kJ/mol. Lastly, the XCs-100, XCs-500, XCs-1000 and XCs-2000 adsorbents presented unimodal pore size distributions (PSDs) centered at a pore radius of 8.38 nm, 7.17 nm, 6.05 nm and 5 nm, respectively. Finally, the estimated thermodynamic parameters such as the adsorption entropy (Sa), the Gibbs free enthalpy (G) and the internal energy (Eint) indicated that DCF adsorption on XCs-500 was spontaneous and exothermic process.

Mathematical modeling approach for the green synthesis of high-performance nanoporous zeolites Na-X optimized for water vapor sorption

A mathematical approach and green synthesis were employed to develop high-performance nanoporous zeolites with a high water vapor sorption capacity and to optimize the synthesis parameters using natural raw kaolin as the starting alumina-silicate material. The Box-Behnken design model with four factors was employed to elucidate the experimental matrix. The physicochemical and structural properties of the synthesized zeolite were characterized using XRD, FTIR, TG/DSC, 27Al and 29Si solid-state MSA NMR spectroscopy, Raman spectroscopy, FE-SEM, and N2 sorption isotherms. The obtained zeolite sample exhibited a BET surface area of 772.19 m2/g and a microspore volume of 0.16 cm3/g. The maximum water vapor uptake capacity at 25 °C and the highest relative pressure was determined to be 12.1137 mmol/g. The isosteric heat of adsorption and average entropy change were calculated to be − 41.340 KJ·K−1 and 115.308 J·mol−1·K−1, respectively. The resulting zeolite demonstrated excellent stability after five consecutive cycles of water vapor adsorption. The experimental data were fitted using five different isotherm and three kinetic models, and the accuracy of each model was assessed using error functions. GAB model and pseudo-first-order kinetic model exhibited the highest correlation coefficient. The nanoporous zeolite sample obtained through the surface response methodology is well-suited for industrial applications.

Investigation of the adsorption mechanism of two nitro musk odorants on OR1A1: Advanced modeling and thermodynamic study

The experimental dose-olfactory response curves of the two nitro musk odorants, such as musk tibetene and musk ambrette, on the broadly human olfactory receptor OR1A1 have been analyzed using four statistical physics models by means of the grand canonical formalism. For such a purpose, the monolayer model with one energy level and the monolayer model with two energy levels were selected to describe the adsorption mechanism of musk tibetene and musk ambrette, respectively. Indeed, three main physicochemical parameters introduced in the selected models affecting the putative adsorption phenomenon involved in the sense of smell, namely, the olfactory response at saturation, the number of nitro musk odorants per OR1A1 binding site, and the half saturation concentration related to the molar adsorption energy. Actually, the investigation of the number of nitro musk fragrances per binding site showed that musk tibetene and musk ambrette odorants were docked on OR1A1 binding sites by a non-parallel orientation and a multi-docking mechanism since the values of this stereographic parameter were higher than unity. Moreover, the selected adsorption models were used to estimate the broadly tuned human olfactory receptor site size distributions relative to musk tibetene and musk ambrette, which were spread out from 1 to 30 nm with a maximum at 4.10 nm for musk tibetene and at 3.55 nm for musk ambrette. Energetically speaking, the magnitudes of the molar adsorption energies, which were inferior to 5 kJ/mol, indicated that the two nitro musk fragrances were physisorbed on OR1A1 binding sites. Furthermore, the adsorption energy distributions, relative to the two olfactory systems, may be estimated to deeply comprehend human olfactory perception, at a molecular level, via the determination of two approximate olfactory bands through the estimation of two adsorption energy distribution bands, which were spread out from 0 to 8.50 kJ/mol for musk tibetene and from 0 to 8 kJ/mol for musk ambrette. Lastly, macroscopically speaking, three thermodynamic potentials governing the adsorption mechanism were studied. Hence, the disorder during the putative adsorption mechanism was followed via the study of the adsorption entropy. Lastly, the adsorption process introduced in the two olfactory systems was spontaneous and exothermic as it was suggested by the Gibbs free energy and the internal energy.

First‐Principles Active‐Site Model Design for High‐Entropy‐Alloy Catalyst Screening: The Impact of Host Element Selection on Catalytic Properties

AbstractActive‐site models comprise miniature active sites on the host element, providing one of effective descriptors for screening high‐entropy‐alloy (HEA) catalysts using machine learning. This study investigates the impact of host elements on the electronic properties of active sites via density functional theory (DFT), where the active‐site model is used in the HEA electrocatalysts. Also, the appropriate host element selection significantly affects the system's surface structures, electronic, and catalytic properties that adsorbate adsorption energy, d‐band center, Bader charge, Zero‐point energy, and entropy are used as accuracy verification parameters compared to the original surface. Ultimately, the novel guideline for active‐site model construction is proposed using the simple example of PtPdFeCoNi high‐entropy alloys. This investigation demonstrates that the host element selection is a crucial parameter to the active‐site models, influencing the electronic structure and electrocatalytic properties.

Tensor renormalization group study of orientational ordering in simple models of adsorption monolayers.

A simple lattice model of the orientational ordering in organic adsorption layers that considers the directionality of intermolecular interactions is proposed. The symmetry and the number of rotational states of the adsorbed molecule are the main parameters of the model. The model takes into account both the isotropic and directional contributions to the molecule-molecule interaction potential. Using several special cases of this model, we have shown that the tensor renormalization group (TRG) approach can be successfully used for the analysis of orientational ordering in organic adsorption layers with directed intermolecular interactions. Adsorption isotherms, potential energy, and entropy have been calculated for the model adsorption layers differing in the molecule symmetry and the number of rotational states. The calculated thermodynamic characteristics show that entropy effects play a significant role in the self-assembly of dense phases of the molecular layers. All the results obtained with the TRG have been verified by the standard Monte Carlo method. The proposed model reproduces the main features of the phase behavior of the real adsorption layers of benzoic, terephthalic, and trimesic acids on a homogeneous surface of metal single crystals and graphite.

Derivation of an Adsorption Isotherm, Chemical Potential, and Entropy for 2D Gas Adsorbates with Packing Exclusions and Attractive Interactions

Derivation of an Adsorption Isotherm, Chemical Potential, and Entropy for 2D Gas Adsorbates with Packing Exclusions and Attractive Interactions

Nigella sativa-Manganese Ferrite-Reduced Graphene Oxide-Based Nanomaterial: A Novel Adsorbent for Water Treatment.

In this study, a novel nanohybrid composite was fabricated via the incorporation of manganese ferrite (MnFe2O4) nanoparticles into the integrated surface of reduced graphene oxide (rGO) and black cumin seeds (BC). The nanohybrid composite was prepared by a simple co-precipitation method and characterized by several spectroscopic and microscopic techniques. The characterization analysis revealed that the rGO-BC surface was decorated with the MnFe2O4. The strong chemical interaction (via electrostatic and H-bonding) between the integrated surface of rGO-BC and MnFe2O4 nanoparticles has been reported. The prepared composite was highly porous with a heterogeneous surface. The average size of the prepared composite was reported in the ranges of 2.6-7.0 nm. The specific surface area of the prepared composite was calculated to be 50.3 m2/g with a pore volume of 0.061 cc/g and a half pore width of 8.4 Å. As well, many functional sites on the nanohybrid composite surface were also found. This results in the excellent adsorption properties of nanohybrid composite and the effectual elimination of methylene blue dye from water. The nanohybrid was tested for various linear isotherms, such as Langmuir and Freundlich, for the adsorption of methylene blue dye. The Freundlich isotherm was the well-fitted model, proving the adsorption is multilayer. The maximum Langmuir adsorption capacity of nanohybrid composite for methylene blue was reported to be 74.627 mg/g at 27 °C. The adsorption kinetics followed the pseudo-second-order recommended surface interaction between the dye and nanohybrid composite. The interaction between methylene blue and the nanohybrid composite was also confirmed from the FTIR spectrum of the methylene blue-loaded adsorbent. The rate-determining step for the present study was intraparticle diffusion. Temperature-dependent studies of methylene blue adsorption were also carried out to estimate adsorption's free energy, enthalpy, and entropy. The methylene blue adsorption was feasible, spontaneous, and endothermic. A comparison study revealed that the present materials could be successfully prepared and used for wastewater treatment.

Moisture sorption isotherms of reduced‐sugar confectionery coatings elaborated with stevia: Mathematical modeling and thermodynamic analysis

AbstractThis work was focused on the study of the adsorption phenomena in reduced‐sugar confectionery coatings elaborated with a high‐intensity sweetener (stevia) as a sucrose substitute. Formulations with different sucrose/stevia contents were elaborated and dried by casting method (60°C for 24 h). Films with dispersed/continuous phase ratios () ranging from 5 (60% sugar) to 2 (0% sugar) were obtained and stored at different temperatures () (5, 25, and 40°C) and water activities (0.206–0.963). Equilibrium moisture contents () were determined by a gravimetric method (drying at 70°C for 6 h and 0.01 atm). The experimental data and phenomena (net isosteric heat and entropy of adsorption) were successfully described through the theoretically‐based generalized D'Arcy and Watt model. An antithetical temperature effect on was observed between 25 and 40°C. Two crossover points were found and affected by and . Novel and industrially‐useful information on reduced‐sugar confectionery coatings was obtained.Practical ApplicationThe sorption of water vapor by foods has received much attention because it is important for evaluating quality changes during storage and for modeling industrial processes. The development of new reduced‐sugar and free‐sugar products is increasing, due to consumers awareness of their well‐being and health. This work presents original research on the mathematical description of the sorption process of reduced‐sugar confectionery coatings elaborated with stevia (a high‐intensity natural sweetener). Four levels of sucrose replacement by stevia and a wide range of storage temperatures (5–40°C) and water activities (0.206–0.963) were analyzed. The information obtained in this work could be useful for researchers and technicians to estimate and control the moisture adsorption performance of sweetened coatings elaborated with traditional (sucrose) and alternative (natural sweeteners) ingredients in practical situations, such as storage and processing.

N-Acetyl cysteine and d-penicillamine as green corrosion inhibitors for copper in 3% NaCl

The corrosion inhibition performance of two amino acid derivatives, N-Acetyl cysteine and D-penicillamine as green corrosion inhibitors of copper in 3% NaCl, in the temperature range of 15–35 °C, was studied by potentiodynamic polarization and impedance measurements. Electrochemical investigations showed the inhibition behaviour of N-Acetyl cysteine and D-penicillamine for copper corrosion with a protection efficiency of ∼ 70%. The adsorption of inhibitors on the copper surface obeys the Langmuir adsorption isotherm and El-Awady kinetic–thermodynamic model. According to the calculated values of Gibbs energy of adsorption (∼−32 kJ mol–1), enthalpy of adsorption (∼−21 kJ mol–1) and entropy of adsorption (42.3 and 34.1 J K–1 mol–1) the adsorption process is exothermic spontaneous chemisorption and physisorption accompanied by an increase in entropy. According to the calculated kinetic activation parameters, the presence of N-Acetyl cysteine and D-penicillamine increases activation energy compared to blank Cu electrode (from 42.3 kJ mol–1 to 56.3 and 56.9 kJ mol–1) indicating strong adsorption of the inhibitor molecules on a copper surface.

Modeling by statistical physics and interpretation of the olfactory process of the two enantiomers 3-mercapto-2-methylbutan-1-ol and 3-mercapto-2-methylpentan-1-ol on the OR2M3 human olfactory receptor

In the present paper, a putative adsorption process of two odorants thiols (3-mercapto-2-methylbutan-1-ol and 3-mercapto-2-methylpentan-1-ol) on the human olfactory receptor OR2M3 has been investigated via advanced models developed by a grand canonical formalism of statistical physics. For the two olfactory systems, a monolayer model with two types of energy (ML2E) has been selected to correlate with the experimental data. The physicochemical analysis of the statistical physics modeling results showed that the adsorption system of the two odorants was multimolecular. Furthermore, the molar adsorption energies were inferior to 22.7 kJ/mol, which confirmed the physisorption process of the adsorption of the two odorant thiols on OR2M3. In addition, quantitative characterizations of both odorants were determined via the olfactory receptor pore size distribution (RPSD) and the adsorption energy distribution (AED), which were spread out from 0.25 to 1.25 nm and from 5 to 35 kJ/mol, respectively. For thermodynamic characterization of the olfactory process, the adsorption entropy indicated the disorder of the adsorption systems of 3-mercapto-2-methylbutan-1-ol and 3-mercapto-2-methylpentan-1-ol on the human olfactory receptor OR2M3. Besides, the used model showed that the presence of copper ions increases the efficacy (olfactory response at saturation) of 3-mercapt-2-methylpentan-1-ol odorant activating OR2M3. The docking molecular simulation indicated that the 3-mercapto-2-methylpentan-1-ol molecule presented more binding affinities (17.15 kJ/mol) with olfactory receptor OR2M3 than 3-mercapto-2-methylbutan-1-ol (14.64 kJ/mol). On the other hand, the two estimated binding affinities of the two odorants belonged to the adsorption energies spectrum (AED) to confirm the physisorption nature of the olfactory adsorption process.

MODELING OF THE WATER ADSORPTION ISOTHERM OF MANGO SLICES (MANGIFERA INDICA L.) DRIED UNDER HOT AIR

The general objective of this work is to contribute to the reduction of post-harvest losses of mangoes by the transformation into stable dried products.This research aims to determine the best storage conditions for dried mangoes.Thus, the water adsorption isotherms of mango slices dried under hot air were experimentally determined by the static thermogravimetric method at 25°C.Eight mathematical models from the literature were used (GAB, BET, Hasley, Henderson, Harking and Dura, Oswin, Chung and Pfost, Smith) to describe the hygroscopic behavior of dried mango slices.Regression analysis was performed using MatLab R2016a software to determine the coefficients, model parameters and statistical parameters of the smoothing.The results revealed that the equilibrium is obtained from 35 days for the two samples and the adsorption isotherms determined are of type II characterized by a sigmoidal shape.In addition, the three-parameter (GAB) model showed good agreement with the experimental data (r= 0.999 and 0.997 respectively for slices with thicknesses of 1cm and 1.5cm) at 25°C.The water content of the mono-molecular layer is 2.295% at 25°C for the 1cm slices and 2.289% at 25°C for the 1.5cm slices.The net isosteric heat of adsorption tends towards zero for high water contents (0.052KJ/mol at 44.472% water).The linearity between enthalpy (net isosteric heat) and differential entropy of adsorption shows their compensation.

Biosynthesis of aluminium oxide nanobiocomposite and its application for the removal of toxic metals from drinking water

This work aimed to synthesize the aluminium oxide nanoparticles using Ixoro coccinea leaf extract. Furthermore, the synthesized Ixoro coccinea aluminium oxide nanoparticles (I–Al2O3-NPs) and nanocomposites (I–Al2O3-NC), including them as the fillers in a chitosan matrix were characterized, and I–Al2O3-NC was applied to remove the toxic metals (TMs) including Cd, Ni, and Pb from water. Optimization of different batch experimental adsorption parameters (pH, concentration of TMs, dose of I–Al2O3-NC, temperature, and time of contact) was done to check the feasibility of I–Al2O3-NC for maximum removal of TMs from water. The extreme adsorption capacities using nanocomposites for Cd, Ni, and Pb were 66.0, 60.0, and 66.4 mg g−1, respectively. The I–Al2O3-NC followed the Freundlich isotherm model for removing Cd and Ni while showing the monolayer surface coverage for the removal of Pb. For this process, the best-fitted kinetic model was the pseudo-second-order equation. The enthalpy, entropy, and free energy of metal ion adsorption, among other parameters of thermodynamics, were estimated. The process was found to be exothermic, advantageous, and spontaneous. Kinetic studies show that intra-particle diffusion is essential for eliminating TMs. In addition, I–Al2O3-NC was applied for the adsorption of TMs from surface water and determined to be effective in removing these contaminants up to an acceptable drinking water standard. Regeneration of adsorbent suggested that green synthesized I–Al2O3-NC may be an active tool for removing Cd, Ni, and Pb ions from contaminated water.