The impact of solvents on the efficiency of cationic dye adsorption from a solution onto protonated Faujasite-type zeolite (FAU-Y) was investigated in the prospect of supporting potential applications in wastewater treatment or in the preparation of building blocks for optical devices. The adsorption isotherms were experimentally determined for methylene blue (MB) and auramine O (AO) from single-component solutions in water and in ethanol. The limiting dye uptake (saturation capacity) was evaluated for each adsorption system, and it decreased in the order of MB-water > AO-water > AO-ethanol > MB-ethanol. The mutual distances and orientations of the adsorbed dye species, and their interactions with the oxygen sites of the FAU-Y framework, with the solvent molecules, and among themselves were inferred from Monte Carlo simulations and subsequently utilized to rationalize the observed differences in the saturation capacity. The dye-solvent competition and the propensity of the dyes to form compact pi-stacked dimers were shown to play an important role in establishing a non-uniform distribution of the adsorbed species throughout the porous space. The two effects appeared particularly strong in the case of the MB-water system. The necessity of including solvent effects in modeling studies is emphasized.

CH 3 -functionalised imogolite nanotubes form extended bundles and the accessibility of their porous structure may vary depending on the surrounding medium.

This chapter describes the use of isothermal titration calorimetry (ITC) to monitor the enthalpy changes accompanying the adsorption of ionic species from dilute aqueous solutions on charged solid surfaces. From the application point of view, it thus covers a broad range of interfacial phenomena of great interest in environmental remediation and catalysis but also in medicinal and pharmaceutical research. The incremental titration procedure is thoroughly detailed together with the subsequent data processing on the basis of appropriate thermodynamic analysis so as to evaluate the cumulative enthalpy of displacement and its changes along the adsorption isotherm in single-solute and two-solute systems. Some illustrative examples of data analysis and processing in selected adsorption systems are presented to highlight the main challenges in correlating the enthalpy balance recorded upon dilution and adsorption calorimetry runs with the measurements of individual adsorption isotherms. It is explained how to exploit the comparison between the measurements carried out in single-solute and two-solute systems in order to get insight into competitive or cooperative effects in ion adsorption at a charged solid-liquid interface. The most important parameters to be controlled or, at least, monitored carefully during the measurements are identified, and their impact on the adsorption mechanisms is discussed.

Water-soluble polymers are attractive materials for pollutants removal thanks to their ability to easily interact with soluble metal cations. In the present contribution, the chemical modification of biocompatible and non-toxic poly(vinyl alcohol) (PVA) was achieved with ethylene diamine tetraacetic acid (EDTA) groups, thus leading to new water-soluble polymers, named PVA(EDTA). Modification was carried out using Mitsunobu?s reaction as an original pathway to obtain statistical copolymers with different EDTA functionalization rates in the PVA chains. Preliminary study about the variation of EDTA rate and chain length permitted determining the optimal polymeric structures. Then, sorption properties of heavy metal (i.e. Co(II), Ni(II), Zn(II), Pb(II), Cd(II), Cu(II)) on structures containing 15% of chelating agent were determined by performing thorough adsorption isotherms or determining removal percentage, at a high or low concentration, respectively. Additionally, the performances of the polymers were tested in a more complex effluent constituted by previous pollutants in the presence of Ca(II) and Mn(II) cations. We demonstrated that water-soluble PVA(EDTA) led to a great improvement of sorption properties in comparison with PVA. Indeed, results obtained showed high sorption capacities for Pb(II), Ni(II), Zn (II), and good selectivity towards some cations, in consistency with EDTA-metal complex formation constants. Isotherm Titration Calorimetry measurements allowed evidencing the complexation stoichiometry, and determining the interaction constant and the enthalpy. This study highlighted the interest of modifying basic commercial polymers with chelating agents for further applications based on Polymer Enhanced Ultrafiltration (PEUF) process.

A computational approach is used on MOF materials to predict the structures showing the best performances for I2 adsorption as a function of the functionalization, the pore size, the presence of the compensating ions, and the flexibility on which to base future improvements in selected materials in view of their targeted application. Such an approach can be generalized for the adsorption of other gases or vapors. Following the results from the simulations, it was evidenced that the maximum capacity of I2 adsorption by MOF solids with longer organic moieties and larger pores could exceed that of previously tested materials. In particular, the best retention performance was evidenced for MIL-100-BTB. However, if the capacity to retain traces of gaseous I2 on the surface is considered, MIL-101-2CH3, MIL-101-2CF3, and UiO-66-2CH3 appear more promising. Furthermore, the impact of temperature is also investigated.

The present paper examines the impact that the nanotube morphology and organic or inorganic intercalated species may have on the cesium sorption by layered vanadium oxides prepared with the use of hexadecylamine as a structure-directing agent. The hybrid material represented by a chemical formula of (V2O5)(VO2)1.03(C16H36N)1.46(H2O)x was achieved through accelerated microwave-assisted synthesis carefully optimized to ensure the best compromise between the scroll-like morphology and the hydrophobic character. To enhance its dispersibility in water, this sample was subsequently modified by progressive replacement of the C16H36N+ units by NH4+ cations. The final materials represented a stacking of lamellar sheets with a worse scroll-like morphology. Both the optimization procedure and the template removal were monitored on the basis of scanning and transmission electronic microscopy, X-ray diffraction, infra-red spectroscopy, inductively coupled plasma-optical emission spectrometry, X-ray photoelectron spectroscopy, and elemental analysis, supplemented by adequate simulations methods providing the reference IR spectra and XRD patterns for comparison or the textural parameters of the samples. The comparison of the cesium sorption from either a 4:1 ethanol–water mixture or aqueous solutions pointed toward the solubility of intercalated cations in the bulk solution as the main factor limiting their displacement from the interlayer space by the oncoming cesium ones. The sample obtained after 70% exchange with NH4+ exhibited a maximum sorption capacity of 1.4 mmol g−1 from CsNO3 aqueous solutions and its retention efficiency remained significant from low-concentration Cs solutions in river or sea water.

In this paper, an extensive characterisation of a range of carbon blacks (CB) with similar surface area but different surface chemistry is carried out by flow calorimetry, Raman spectroscopy, dynamic water vapour sorption, instrumental gas analysis, nitrogen adsorption/desorption and high potential chronoamperometry. Using these carbon materials as supports, Pt/CB electrocatalysts are prepared by microwave-assisted polyol-mediated synthesis in gram scale. Structural, morphological and electrochemical properties of the prepared electrocatalysts are evaluated by X-ray diffraction, transmission electron microscopy, rotating disc electrode and in situ fuel cell characterisation of the corresponding membrane-electrode assemblies. The obtained results allow to establish a relationship between surface chemistry and electrochemical properties useful for the design of Pt/C catalyst layers with high performance and stability.

In view of potential uses in short-term thermochemical heat storage by sorption of water vapor, the capacity to release a sufficient heat amount at the appropriate rate of a Prussian blue analogue (PBA) containing hexacyanocobaltate vacancies has been compared with those of 13X type zeolites possessing Na+, Ce3+, Ce4+, or Tb3+ extra-framework compensating cations. The extended structural and surface characterization demonstrated good reproducibility of the preparation procedures performed on a 10-g scale. The adsorbents were tested under dynamic conditions of gas flow with the aid of either a gas flow calorimeter (120 mL h−1 helium flow) to measure the amount and rate of the integral heat release or a laboratory-scale test rig (15,000 to 22,800 mL h−1 nitrogen flow) to monitor the outlet temperature of nitrogen heated by adsorption. For a regeneration temperature of 353 K and a partial H2O pressure of 2.8 kPa in helium, the PBA sample yielded an integral heat ranging between 900 and 1020 kJ kg−1 with a very slow heat release lasting for even 12–14 h. The zeolite-based materials generated between 350 and 950 kJ kg−1 more rapidly (up to 6–7 h), depending on the nature and the content of compensating cations, as well as on the dehydration state achieved during regeneration. With the laboratory-scale test rig, the efficiency of heat extraction by convection was about 65% for Na-13X and only 38% for PBA, and it diminished with decreasing flow rate.

Three ionosilica materials have been tested for low-temperature thermochemical storage of energy under mild conditions of adsorbent regeneration and saturation. The previous synthesis procedures were adapted to prepare materials possessing an organosilica framework with silylated cationic blocs and Cl-, HSO4-, SO42- anions in various proportions as extra-framework compensating counter-ions. Transmission and Scanning Electron Microscopy, Wavelength Dispersive X-Ray Fluorescence, Energy Dispersive X-ray Spectroscopy, Thermogravimetric analysis, adsorption of gaseous nitrogen at 77 K, Si-29 Solid-State Nuclear Magnetic Resonance spectroscopy were employed to establish the key characteristics of the three ionosilica samples in terms of elemental composition, particle morphology and textural properties, thermal stability and regenerability, or variability of surface activity during repeated hydration-dehydration cycles. Their capacity to adsorb water vapor at cool and moderate ambient temperatures after incomplete surface drying was demonstrated by means of the scanning microscopy operating in low-vacuum mode at 275 K, or more precisely by measuring the water adsorption isotherms at 313 K and the related differential heats under static conditions. Finally, flow calorimetry operating in the moist-gas flow mode was used to measure the integral heat accompanying the adsorption of water vapor at its partial pressure of 2.8 kPa and 296 K as well as the kinetics of heat release in three drying-saturation cycles. After a drying procedure carried out under helium flow at 353 K, the thermal performance of two ionosilica samples containing both HSO4- and SO(4)(2-)counter-ions was sufficient enough to consider them as potential adsorbents for auxiliary space heating in homes, small businesses, or public buildings.

The understanding of the mechanism of co-operative adsorption of Co(II) cations and acetate or citrate anions onto gamma-Al2O3 from aqueous solutions has been refined on the basis of comparison between the enthalpies of displacement measured in single-solute and bi-solute systems by means of isothermal titration calorimetry. The data processing procedures were adapted to take into account the occurrence of a cobalt-ligand complex in the bulk solution. Considering the bridging role of the adsorbed cobalt cations as a starting point to reproduce the enthalpy of displacement in the cobalt-acetate system, each ligand unit was suggested to bind preferentially to more than one adsorbed metal species and to interact additionally with some electrically neutral binding sites on the oxide surface. In the case of cobalt-citrate couple, the formation of a 1:1 stoichiometry solid-ligand-metal complex and simultaneous adsorption of cobalt cations as bidentate inner-sphere complexes reproduced best the experimental data.

The potential use of commercially available 13X zeolite, modified by ion-exchange with cerium compensating cations possessing high charges and high hydration energies, has been tested in view of low-temperature storage of solar energy performed under mild operating conditions of low regeneration temperatures and low pressures of water vapour during the adsorption step. Structural and textural properties, sorption behaviour towards water vapour of three selected samples containing various proportions of Ce3+ and Ce4+ compensating cations and the pristine Na+-13X zeolite were studied by a variety of experimental techniques including Wavelength Dispersive X-Ray Fluorescence, Energy Dispersive X-ray Spectroscopy, X-ray diffraction, Thermogravimetric analysis, as well as measurements of the adsorption of gaseous nitrogen at 77 K and water vapour at 313 K. Based on the structure refinement procedure applied to the experimental XRD patterns, it was demonstrated that extra-framework cerium cations were preferentially located on sites I' and II in dry and hydrated zeolites, showing relatively little dependence on the hydration level. Monte Carlo simulations were used to determine the limit values of the amount adsorbed and differential heat of adsorption, which could be obtained experimentally if the zeolite samples were completely dried. The potential of Ce-containing zeolites as adsorbents for the thermochemical energy storage was finally determined under flow conditions by firstly dehydrating samples at 353 K or 423 K and then saturating them at 296 K with water vapour at a mole fraction of 0.03. The choice of the operating conditions was decided so as to maintain the stability of the zeolite structure while taking the risk of reduced thermal performance of zeolite adsorbents undergoing incomplete regeneration-dehydration. Under such mild conditions, the modified 13X zeolites exhibited enhanced thermal performance in comparison with that of the pristine 13X, by releasing between 700 and 1100 kJ per kg of the adsorbent during a period of 6-8 h. Through a complementary study based on calorimetry measurements and molecular simulations, the understanding of the hydration-dehydration steps in Ce-exchanged zeolites and cation displacement upon hydration has allowed to establish the best compromise for the conditions of zeolite regeneration and saturation in the case of heat long-term storage applications.

The present report deals with low-temperature thermochemical storage for space heating, which is based on the principles of vapour adsorption onto solid adsorbents. With the aim of obtaining comprehensive information on the rationalized selection of adsorbents for heat storage in open sorption systems operating in the moist-air flow mode, various materials reported up to now in the literature are reviewed by referring strictly to the possible mechanisms of water vapour adsorption, as well as practical aspects of their preparation or their application under particular operating conditions. It seems reasonable to suggest that, on the basis of the current state-of-the-art, the adsorption phenomenon may be rather exploited in the auxiliary heating systems, which provide additional heat during winter’s coldest days.

The molecular mechanism of Methyl Orange (MO) dye adsorption on the external surface of Mg2Al–CO3 layered double hydroxide (LDH) was investigated by combining adsorption isotherms, X-ray diffraction, and infrared (IR) and Raman spectroscopies coupled to DFT calculations. The vibrational dynamic behavior upon adsorption and the molecular surface organization were correlated with the adsorption isotherm revealing a four-domain uptake mechanism. The peculiar high adsorption capacity of LDH toward MO was explained by the surface-promoted dye aggregation over the external surface of particles.

The present contribution aims at reporting the synthesis and the preliminary evaluation of hybrid materials combining polyvinyl alcohol (PVA) functionalized with ethylenediaminetetraacetic acid (EDTA) as complexing groups, and alumina that, together, were able to efficiently complex and remove metallic cations from aqueous effluents. For such purpose, well-defined PVA homopolymers bearing an azide (PVA-N3) or an alkyne function (PVA-alkyne) were functionalized via chemical modification by either phosphoric acid (PPVA-N3), to promote adhesion to alumina, or ethylenediaminetetraacetic acid (PVA(EDTA)-alkyne), able to efficiently complex metallic cations. Modified PVA chains were coupled by Huisgen reaction using copper catalysis (CuAAC) leading to the formation of bifunctional diblock copolymers. Then, hybrid materials were produced via the grafting of PVA-based copolymers onto alumina particles. Finally, the sorption capacity of these materials towards Co(II), Ni(II) and Sr(II) was determined to evaluate their removal efficiency. Such hybrid materials could be efficiently used in the context of nuclear effluents treatment.

An alternative microwave-assisted hydrothermal route for the preparation of manganate nanoflowers under basic conditions has been proposed in view of potential uses in selective retention of strontium from multicomponent aqueous streams. Based on the combination of such characterization techniques as Scanning and Transmission Electronic Microscopy, X-ray photoelectron spectroscopy, and X-ray Diffraction, as well as taking advantage of the computer-aided structure simulation, homogeneous nanoflower morphology possessing a layered structure and K+ compensating cations was evidenced as corresponding to the KMn4O8 chemical formula. The nanoflower sample was subsequently tested for the selective adsorption of strontium and cesium by measuring the individual adsorption isotherms from single-solute and multicomponent aqueous solutions. The material appeared selective towards strontium against cesium even in multicomponent solutions provided that the concentration of calcium remained low. This difference in the retention selectivity was rationalized based on the Density Functional Theory (DFT) calculations of the energy of adsorption and direct calorimetry measurements of the enthalpy of displacement for the individual cations.

This study analyzes the effect of the addition of acetate, citrate, and nitrilotriacetate anions on the retention of Co(II) cations by the γ-alumina surface in view of the preparation of alumina supported cobalt catalysts. The emphasis was placed on the way the Co(II) species attach to the solid surface when adsorbed from aqueous solutions under the unadjusted pH condition. The individual adsorption isotherms onto γ-Al2O3 support for cobalt and a given ligand were determined by following the solution depletion method in single-solute and bi-solute systems. These adsorption data were supplemented by the results of potentiometric titrations. In the case of bi-solute systems, the adsorption procedures allowed either co-impregnation of γ-alumina with equimolar solutions of cobalt and ligand salts or pre-impregnation of γ-alumina with the ligand anions and the subsequent adsorption of cobalt. Changes in the pH of the equilibrium solid-liquid suspension were also monitored along the adsorption isotherms. The adsorption of Co(II) onto γ-Al2O3 in the presence of acetate and nitrilotriacetate led to the formation of the type A (i.e., solid-metal-ligand) ternary complexes. The use of citrate anions together with Co(II) cations was shown to improve the impregnation process through the formation of ternary complexes of type B (i.e., solid-ligand-metal). The comparison with a system containing tricarballylate anions allowed concluding that the presence of the hydroxyl group in the citrate anion enhanced its affinity for the alumina surface by contributing to the inner-sphere character of its surface-bound complexes.

Theoretical and experimental characterization methods have been combined to shed more light on the potential impact of the various templating amines that they may have on the formation of layered vanadates with a scroll morphology and their cation-exchange capacity. Eight branched- and straight-chain alkylamines were used as the structure-directing agents to make the V2O5 sheets roll up into a scroll structure during microwave-assisted hydrothermal synthesis. The as-synthesized materials were characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), and elemental analysis in order to obtain the necessary information on their nanostructure and morphology as a function of the template. On the basis of these experimental results, the density functional theory (DFT) calculations completed with Monte Carlo simulation methods were applied to model the template conformation and the way it had been intercalated into the vanadate layers. It was then postulated that similar structuring mechanisms had been involved in the formation of different hybrid nanotubes with amine molecules forming tilted bilayers of overlapping hydrocarbon tails. In line with what one would expect from the hypothesis that the driving force of vanadate scrolling is due to a partial reduction of V(V) to V(IV) induced by interactions of amine template with the 2D V2O5 layers, the variations in the surface charge density were monitored by studying the cation-exchange capacity of the samples prepared previously by exchanging the amine units for ammonium cations. Then the isotherms for ion exchange of cesium onto such samples from aqueous solutions were measured by the solution depletion method. The use of cesium to probe the surface density of negative charge can also be regarded as viable in view of potential application of vanadate nanotubes in radioactive wastewater treatment.

The contribution of isothermal titration calorimetry is discussed to elucidate the mechanism of competitive adsorption of free Ca2+, Sr2+, Ba2+, and Cd2+ cations onto 4A-type zeolite from aqueous solutions at 298 K. The individual adsorption isotherms for these cations and the related enthalpy of displacement curves were compared between single-metal and two-metal systems. Separate dilution runs carried out under the same experimental conditions provided evidence that the dilution phenomenon made no significant contribution to the total cumulative enthalpy effect. In the light of the observations made in the present study, it is postulated that divalent cations exchanged with extra-framework sodium in different crystallographic locations within the zeolite structure. The binding affinity of individual cations for the zeolite surface was established to decrease in the following order: Sr approximate to Ba > Cd > Ca, in line with the increasing endothermic character of the displacement process. The experimental Delta H-dpl(cum) values in two-metal systems were also compared with the theoretical ones obtained by summing up the individual metal contributions as measured in appropriate single-metal systems. In the case of the Sr(II) + Cd(II) system, the competition became noticeable above a total amount adsorbed of 1 mmol g(-1), as indicated by great differences between the experimental and theoretical enthalpy values. For the Sr(II) + Ba(II) and Sr(II) + Ca(II) systems, the sequence of site occupation was found to be modified as a result of competition. The effect was particularly pronounced for strontium which gave more exothermic contribution to the total enthalpy of displacement.

We report ionosilicas with different chemistries, textures, and morphologies and their use as adsorbents for chromium(VI). All studied materials are highly efficient anion exchange materials with adsorption capacities between 1.6 and 2.6 mmol/g. The ion exchange capacity of the materials reaches up to 91% of the theoretical value, that is, the molar amount of ionic groups immobilized within the material, indicating a very high accessibility of the organo-ionic groups. Noticeable differences were found regarding the ion exchange properties in terms of capacity and kinetics according to the used material, in particular, its porosity. High specific surface areas favor the adsorption process and result in high adsorption capacity. However, even a nonporous material displays high adsorption capacity of 1.7 mmol/g. This result can be attributed to the high hydrophilicity of ionosilicas that favors diffusion and mass transfer throughout the material. The adsorption kinetics are fast, as 80-90% of the adsorption capacity is reached after similar to 10 min. Finally, isotherm titration calorimetry evidences the influence of the constitution of the cationic group the displacement enthalpy, in relationship with the steric hindrance of the alkyl groups that surround the cationic center.

Rod-shaped mesoporous silica nanoparticles (RMSN) with built-in gold nanoparticles or thin gold nanowires in the pore channels were in situ synthesized via a one-step procedure. The insertion of a hydrophobic gold precursor into the mesopores of RMSN was reached through a micellar solubilization mechanism and gold nanoparticles were achieved through a thermal reduction. The resulting RMSN and Au-RMSN samples were characterized by using X-ray diffraction, transmission and scanning microscopies (TEM and SEM), X-ray photoelectron spectroscopy (XPS), nitrogen physisorption and solid-state Nuclear Magnetic Resonance (NMR). The interaction of Au precursor (a carbene complex) with the thiol group at the silica surface was identified and found to play a crucial role in the dispersion of the uniform metal nanoparticles at the internal surface of RMSN. Moreover, TEM micrographs revealed the absence of large gold particles outside the mesopore network. The shape of Au nanoparticles and their loading amount in the mesoporous silica could be easily tuned by altering the concentration of gold precursor.