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• Sonication improves moisture removal from activated alumina compared to heating. • Replacing 20% of heat (25 W) with ultrasound results in 27% desorption energy saving. • Ultrasonic-induced alteration in surface energy is postulated as an enhancement mechanism. • Effect of ultrasonic radiation becomes more significant at lower frequencies. • Sonication reduces regeneration temperature without lowering desorption rate. Desorption processes are important part of all processes which involve utilization of solid adsorbents and are inherently energy-intensive. Here we investigate how those energy requirements can be reduced through the application of ultrasound for the activated alumina/water adsorption pair. To analyze the energy-saving characteristics of ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no ultrasound at the same total input power. Duplicate experiments were performed at three nominal frequencies of 28, 40 and 80 kHz to observe the influence of frequency on regeneration dynamics. Regarding moisture removal, the highest desorption was achieved at the lowest ultrasonic-to-total power ratio corresponding to about 27% reduction in energy consumption. A nonlinear inverse proportionality was observed between the effectiveness of ultrasound and the frequency at which it is applied. Regarding regeneration temperature, application of ultrasound at higher ultrasonic-to-total power ratios of 0.4 and 0.5 reduces the regeneration temperature without taking a toll on desorption. Based on the variation of desorption dynamics with ultrasonic power and frequency, a novel ultrasound-enhanced desorption mechanism involving adsorbate surface energy is proposed and a relationship between acoustically induced strain and adsorbate surface energy is introduced. An analytical model that describes the desorption process is developed based on the experimental data. From this a novel efficiency metric is proposed, which can be employed to justify incorporating ultrasound in regeneration and drying processes. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report a research of bulk pyrolysis of sucrose in the presence of activating agents. [•] Microporous carbons were formed by non-catalytic bulk carbonization of sucrose. [•] Carbons with increased V micro and V supermicro were obtained in the presence of H3PO4. [•] Mainly mesoporous carbons were formed in the presence of zinc chloride. [•] Thermal activation with steam results in the significant increase of H2 adsorption. [ABSTRACT FROM AUTHOR]

Recent theoretical and simulation studies (Lueking et al. Phys Rev B 75:195425, ; Kim et al. J Phys Chem 115:7249-7257, ) on the adsorption of Kr on suspended nanotubes yielded different commensurate phases at submonolayer coverage than those found in a pioneering experiment (Wang et al. Science 327:552-555, ). This controversy between calculations and experiments is yet to be resolved. One of the tentative explanations of the apparent discrepancy is the possibly different chirality as the chirality of the nanotubes used in the experiment is not known. To address the question on chirality, we calculated the adsorption potential of krypton atoms on two sets of single wall carbon nanotubes of same radii with distinct chiralities. We found novel symmetries of the adsorption sites on a nanotube, which systematically vary depending on its chirality with an unexpected, yet intuitive delicacy. The same approach is equally feasible for other gases (Ar, Xe, CH $$_{4}$$ , etc.). The results of classical grand canonical Monte Carlo simulations confirm the predicted behavior of adsorption phases. [ABSTRACT FROM AUTHOR]

The adsorption potential in the interior of an infinite nanopore along the z-axis, with varying radius R( z), is derived as a function of a deformation parameter. Detailed calculations for a carbon nanotube indicate that according to the magnitude of the deformation the potential landscape can be substantially modified, giving rise to regions of weakened confining strength, and even changing the nature of the minima. This modified field may induce thermodynamic instabilities in the adsorbed fluid. A similar situation takes place for other materials, such as alkaline pores with variable cross-section. A general argument can be provided that explains the origin of such instabilities. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a detailed experimental study combined with Monte Carlo (MC) simulations within the primitive model of the physical chemistry at the ettringite–water interface over a wide range of pH and bulk conditions for which ettringite exists thanks to its solubility in aqueous solutions. Ettringite, which is an important phase in hydrated cement-based systems, bears a permanent and positive structural charge. In contrast with previous studies, electrokinetic measurements together with the careful chemical analysis of the equilibrium solutions of the dispersions have brought strong support to designate sulfate as being the ion determining the potential. Simulations showed that electrostatics, through ion–ion correlations, are not strong enough to explain the charge reversal of ettringite immersed in sulfate salt solutions. However, an excellent agreement between simulated and experimental data was obtained including a short-range nonelectrostatic adsorption potential for the sulfate ion. This result strongly suggests the existence of a chemical specificity of sulfate ions for an ettringite surface. [ABSTRACT FROM AUTHOR]

Abstract: Nitrobenzene at a relatively high concentration was reported to cause an environmental pollution event in Songhua River, China in 2005. The adsorption characteristics of nitrobenzene on the surficial sediments (natural surface coatings) were investigated via a selective extraction – adsorption – statistical analysis method. The experimental results show that the changes in the adsorption potential are not always consistent with the variation of particle structure, suggesting that the effect of removal of some components by extraction or separation procedures on the adsorption potential is much greater than that of variation of particle structure. An additional model analysis indicates that not only organic materials but also Fe oxides, Mn oxides and clay minerals contribute much to the adsorption of nitrobenzene. But the adsorption capacity of Mn oxides on a unit mass basis is the highest, and the lowest for clay minerals except for silicate minerals, implying that the role of organic materials and clay minerals in the solid particles contributed to binding of nitrobenzene is less than that of Fe and Mn oxides, especially the later. The new evidence for the higher adsorption potential of nitrobenzene on the surficial sediments (natural surface coatings) and the more importance of Mn oxides contributed to nitrobenzene adsorption is showed in the present study supposing that the adsorption capacity of solid particles can be divided into several fractions. [Copyright &y& Elsevier]

The method of adsorption porosimetry (AP) has been long known in physical chemistry of porous sorbents, but its practical application was limited to studies of massive samples of such materials as silica gels, zeolites, etc. We have developed a technique to study the porous structure of dielectric thin films ( d ∼ 100 nm). It is stated that it provides us with quite novel information which permits the prediction of properties of dielectric layers and makes it possible on this basis to solve optimization problems of technological processes. The use of ellipsometry has further extended the potential of this method, and currently it is a powerful nondestructive technique to measure porosity and the size distribution of pores in thin layers for the purposes of modern electronics. [ABSTRACT FROM AUTHOR]

• Polanyi adsorption potential theory is introduced to analyze methane adsorption. • The accuracy of different methods for excess adsorption correction is discussed. • Effect of adsorbed phase density on excess adsorption correction is investigated. • The adsorbed phase density may be in the vicinity of 0.30 g/cm3 to 0.40 g/cm3. In order to evaluate the accuracy of different methods for the methane excess adsorption correction, the Polanyi adsorption potential theory was introduced to analyze the absolute methane adsorption amount obtained by correction. One shale sample from the Lower Silurian Longmaxi Formation in the southern Sichuan Basin, China was selected to conduct high-pressure methane adsorption experiments at 40.6 °C, 60.6 °C, 75.6 °C, and 95.6 °C at pressures up to 52 MPa. Based on the experimental results at different temperatures, four densities (the liquid density of methane at boiling temperature and ambient pressure, the van der Waals density, the adsorbed phase density based on the falling segment fitting of excess adsorption isotherm, and the adsorbed phase density obtained by fitting excess adsorption isotherm using modified Langmuir equation) were used for the correction of excess adsorption to absolute adsorption. At the same time, in order to enhance the reliability and accuracy of the conclusions in this study, the results of methane adsorption experiments on shale in the reference were used for a comparative study to further support our conclusions. The results indicate that the greater the constant adsorbed phase density used for the excess adsorption correction, the lower the degree of overlap of the adsorption characteristic curves at different temperatures. The adsorbed phase density used for methane excess adsorption correction may be in the vicinity of 0.30 g/cm3 to 0.40 g/cm3. Particularly, it should not be greater than the liquid density of methane at boiling temperature and ambient pressure, which is 0.421 g/cm3. Although the adsorbed phase density differs across different temperatures and pressures, the current results show that 0.373 g/cm3 can be used as the adsorbed phase density for the excess adsorption correction, which may be a convenient method and can yield results close to the actual adsorption. [ABSTRACT FROM AUTHOR]

Simple isotherm models can fit microporous adsorption yet the molecular interactions underlying the successful fitting have often remained obscure. Here we demonstrate how semi-empirical isotherm model data can be mined to reveal the reality of adsorbate-adsorbate molecular interactions. This was made possible by the fluctuation adsorption theory, a rigorous theory based only on the principles of statistical thermodynamics. For microporous carbons, adsorbate-adsorbate interactions quantified from the Dubinin-Radishkevich (DR) and Dubinin-Astakhov (DA) models successfully capture the primary micropore filling mechanism and the subsequent layer adsorption, leading to a liquid-like behaviour of the adsorbates. The microscopic meanings of the DR and DA parameters and the adsorption potential have also been clarified via statistical thermodynamics. [Display omitted] • A novel statistical thermodynamic approach to adsorption has been developed. • Adsorbate-adsorbate interaction can be quantified from semi-empirical isotherm models. • Molecular basis of Dubinin-Radishkevich and Dubinin-Astakhov models clarified. • Adsorbate-adsorbate interactions support the proposed adsorption mechanisms. • Physical meaning of the "adsorption potential" was clarified. [ABSTRACT FROM AUTHOR]

To study vicinal water structure around polystyrene latex particles differential thermal analysis (DTA) has been utilized. Measurements of programmable water thermodesorption from polystyrene surfaces under dynamic and quasiisothermal conditions were made. Therefore, the adsorption potential distribution function was calculated and the hydrophobicity of polystyrene surfaces determined. DTA is presented as a useful method to study the interfacial properties of polymer colloids. [ABSTRACT FROM AUTHOR]

• Nuclear magnetic resonance features of methane in tectonically deformed coal. • Influence of pore structure on the occurrence of adsorbed and free methane. • Impact of adsorption potential on the occurrence of adsorbed and free methane. Differences in pore and surface free energy affect the occurrence of adsorbed and free methane in tectonically deformed coal (TDC), which influences coalbed methane extraction and coal mine safety. Therefore, eight middle-rank TDC samples from the Yueliangtian coal mine (Guizhou Province, Southwest China) were screened. Pore volume and specific surface area were explored via mercury intrusion, nitrogen adsorption/desorption, and carbon dioxide adsorption approaches. Based on the low-field nuclear magnetic resonance analysis for powdered TDC, the relaxation time (T 2) amplitudes and the contents of adsorbed and free methane, the surface free energy reduction (SFER), and adsorption potential were measured. 1) The pore specific surface area, pore volume, T 2 amplitudes and contents of adsorbed and free methane, SFER, and adsorption potential of the strongly deformed coal are obviously larger than those of the weakly deformed coal. Adsorbed methane content is dominantly affected by micropore specific surface area, and free methane content is primarily influenced by macropore volume. 2) The methane T 2 spectra of the TDC contain three distinctive peaks; the first, P 1 (T 2 < 2 ms), represents adsorbed methane, and the second, P 2 (2–40 ms), corresponds to free methane. As the pressure increases, both the T 2 amplitude rate and content rate of adsorbed methane decrease, while those of free methane rise. 3) With the enhancement of tectonic deformation, the specific surface area and volume of pores increase (especially those of micropores and macropores), more adsorption positions and storage space for adsorbed and free methane become available, and the SFER and adsorption potential of the TDC are enhanced, leading to increases in the T 2 amplitudes and contents of adsorbed and free methane. The present research will help improve the accuracy of coalbed methane evaluation and the prevention of coal and gas outbursts. [ABSTRACT FROM AUTHOR]

Recently, owing to the discovery of graphene, porous carbons experienced a revitalization in their explorations. However, nowadays, the focus is more on search for suitable energy advancing catalysts sensing, energy storage or thermal/light absorbing features than on separations. In many of these processes, adsorption, although not emphasized sufficiently, can be a significant step. It can just provide a surface accumulation of molecules used in other application-driving chemical or physical phenomena or can be even an additional mechanism adding to the efficiency of the overall performance. However, that aspect of confined molecules in pores and their involvement in the overall performance is often underrated. In many applications, nanopores might silently advance the target processes or might very directly affect or change the outcomes. Therefore, the objective of this communication is to bring awareness to the role of nanopores in carbon materials, and also in other solids, to scientists working on cutting-edge application of nonporous carbons, not necessary involving the adsorption process directly. It is not our intention to provide a clear explanation of the small pore effects, but we rather tend to indicate that such effects exist and that their full explanation is complex, as complex is the surface of nanoporous carbons. [ABSTRACT FROM AUTHOR]

Water content, metamorphism (coal rank) particle size, and especially pore structure, strongly influence the adsorption capacity of coal to methane. To understand the mechanism of methane adsorption in different rank coals, and its controlling factors, isothermal adsorption experiments with different coal ranks, moisture contents and particle sizes at the temperature of 303.15 K were conducted. In addition, the pore structures of coals were investigated through N2 adsorption/desorption experiments at the low-temperature of 77 K for selected coals from the Junggar Basin of NW China, Qinshui Basin and Ordos Basin of north China. Moreover, the adsorption potential of methane on the surface of the coal matrix was calculated, the controlling factors of which were discussed. The obtained methane isothermal adsorption result shows that the Langmuir volume (VL) of coal is independent of the particle size, and decreases with the increase of moisture content, which decreases first and then increases when the coal rank increases. Combined with the pore structure by the N2 adsorption at 77 K, VL increases with the increase of pore surface area and pore volume of coal pores. Besides, the adsorption potential of all selected coals decreased with the increase of the methane adsorption volume, showing a negative relationship. The interesting phenomena was found that the surface adsorption potential of the coal matrix decreases with the increase of moisture content, and increases with the decrease of particle size at the same pressure. With the same adsorption amount, the adsorption potential on the surface of coal matrix decreases first, and then increases with the increase of coal rank, reaching a minimum at Ro,m of 1.38%, and enlarging with the increase of pore surface area and the pore volume of coal pores. These findings may have significant implications for discovering CBM accumulation areas and enhancing CBM recovery. [ABSTRACT FROM AUTHOR]