On-surface synthesis of C–C covalent low-dimensional nanomaterials is a promising method of obtaining structures with tailored and novel physicochemical and electric properties. In this contribution, the Monte Carlo simulation approach was proposed to predict the topology of metal–organic (MO) intermediates formed in the Ullmann homocoupling of halogenated isomers of tetracene. The coarse-grained model of polyaromatic hydrocarbons (PAH) haloderivatives and divalent copper adatoms on a metallic crystal surface (111) was used, where locations of substituents in the molecules were encoded as active centres with directional C–Cu interactions. The computations were performed for various structural isomers of tetracene, from disubstituted to tetrasubstituted units. As a result, diverse superstructures were obtained, such as dimers, trimers, and other oligomers, chains and ladders, and metal–organic (MO) networks, both chiral and achiral. Additionally, for the prochiral linkers, simulations of the racemic mixtures were performed. Our study provided useful insight into the influence of substituents’ position and the carbon backbone’s size on the topology of the modelled precursor architectures.

In this study four kinds of biochars were prepared from the KOH modified biomass. As the carbon precursors there was used the sawdust from the following trees: oak, hornbeam, apple and cherry. The physicochemical properties of the materials were characterized by the N2 adsorption, scanning electron microscopy, thermal analysis (TG, DTG and DTA), infrared spectroscopy, and the Boehm’s titration method. Moreover, pHpzc (the point of zero charge) was determined. The adsorption capacity and the temperature-programmed desorption of ammonia were also studied. The obtained activated biochars were characterized by the large specific surface area (672 to 912 m2/g) and the total pore volume (0.30 to 0.4 cm3/g) as well as the well-developed microporous structure (85–97%). These observations were also confirmed by the SEM analysis. The maximum NH3 adsorption capacity of the activated biochar was determined to be 3.05 mmol/g. These results prove that the sawdust of various origins is appropriate to prepare a cost-effective, environmentally friendly biochar.

This paper is dedicated to the memory of Academician Mikhail Mikhailovich Dubinin (1901–1993), the eminent Russian scientist who made an outstanding contribution to adsorption science—one of the most important subdisciplines of physical chemistry. A brief account of his life, professional carrier, and scientific achievements is presented.

The effects of crosslinker and dye type on swelling and S-type adsorption properties of crosslinked polyhydroxamates (CHP) were investigated. CHPs containing N,Nʹ-methylenebisacrylamide (N), or ethylene glycol dimethacrylate (E) were used in the swelling, diffusion, and adsorption experiments in solutions of oxazine dyes such as Brilliant Cresyl Blue, Nile Blue, and Cresyl Violet. Swelling and diffusion parameters of CHPs in dye solutions (such as equilibrium swelling, half time of swelling, swelling value at half time, network parameter, diffusion exponent, and diffusion constant) were calculated. It is understood from the time of swelling to reach equilibrium that CHPs swell very fast. CHP-E in all dyes solutions swelled considerably more than CHP-N. Dye solution diffusion into CHPs was determined to be of non-Fickian character. It has been observed that the swelling properties of hydrogels are highly influenced by the crosslinker type. The adsorption of oxazine dyes onto CHPs is similar to the S-type adsorption in the Giles classification system. When it was seen that the experimental data fit the Sigmoidal 4 parameter equation with a high correlation (r2 > 0.995), the use of this equation determined the adsorption parameters such as the highest bonding rate or monolayer coverage, the transition point of the isotherm, the magnitude of the absorbent's absorbability and the slope parameter. Site-size, maximum fractional occupancy, the binding ratio at the transition point, binding constant, the initial binding constant, partition coefficient, and adsorption free energy values were also calculated by using the found adsorption values. Dye adsorption from all dyes solutions to CHP-E is considerably higher than CHP-N. An increasing linear relationship was found between swelling and adsorption. In conclusion, the sigmoidal equation approach can be a useful tool for chemists, chemical, agricultural and environmental engineers, polymer scientists to find the adsorption parameters of polymer adsorbents, and at the same time, it can be said that CHP can be used as a good sorbent in the removal of some chemical agents (such as dye molecules, organic molecules, biologically active molecules).

A demand-driven pressure swing adsorption biogas upgrading application is modelled using monolayer and multilayered (bilayer) beds, to gain insight on the impact of the adsorbent pellet size on the overall performance of such processes. Pellet radii in the range of 0.1–2.4 mm were studied, for fixed cycle settings and column dimensions. Varying the pellet size influences the sorption kinetics and flow resistance, resulting in the existence of an optimum pellet size for monolayered beds. For fixed cycle settings, small pellets may yield higher purities at low total productivities, yet show a more rapid decrease in product purity with increasing productivities due to the higher pressure drop. Furthermore, 18 configurations with beds containing a layer of larger pellets and a second layer of smaller pellets (bilayer) were investigated. Bilayered beds with 0.3 mm, 0.6 and 2.4 mm radius pellets were combined, with the first layer taking up 25, 50 or 75% of the bed. With respect to upward flow in the adsorption step, beds with the smallest pellet size in the top layer (LS beds) can offer higher product purity than beds with the smallest pellet in the bottom layer (SL beds).

A new non-experimental methodology based on a 3D Navier–Stokes (NS) computational fluid dynamics (CFD) model in lieu of experiments, is proposed for developing 1D axial pressure drop correlations for structured adsorbents with parallel channels. To demonstrate the methodology, a 1D correlation was developed by fitting and validating a Darcy–Weisbach (DW) type expression against the 3D-NS model. The methodology was further validated by contrasting the 1D-DW correlation against bench-scale experimental data obtained from a Catacel structured adsorbent with parallel triangular channels and against two 1D pressure drop correlations in the literature for parallel triangular channels. A wide range of velocities, pressures, channel dimensions and gas molecular weights were explored. To resolve the 1D-DW correlation, expressed in terms of a Darcy friction factor involving two fitting parameters f1 and f2, an analytic expression derived from the differential 1D-DW model was simultaneously regressed with all the results obtained from the 3D-NS model using air at 25 °C. Then predictions from the differential 1D-DW correlation, now solved numerically in COMSOL 5.2, were contrasted against those from the 3D-NS model for the same conditions using CO2 and He in addition to air at 25 °C. The 1D-DW correlation agreed well with the 3D-NS model, with the average and standard deviation of the average relative errors (AREs) being 1.79% \(\pm \) 1.89%. The 1D-DW correlation also showed good agreement with experiment for all outlet pressures and gases. The average and standard deviation of the AREs were 10.96% \(\pm \) 5.59%. Additionally, the 1D-DW correlation agreed well with the Boussinesq, and Shah and London correlations, with the average of the AREs relative to the 3D-NS model respectively being 2.00, 2.47 and 6.17%. These results validated the new non-experimental procedure for developing 1D axial pressure drop correlations from 3D CFD modeling in lieu of experiments. This new methodology is applicable to virtually any structured adsorbent shape with parallel channels and is especially advantageous where experiments might be problematic.

Nanoporous carbon sorbents modified with oligomers of lactic and glycolic acids were synthesized without the use of catalysts and organic solvents. Their synthesis includes impregnation of the sorbent with a 50% aqueous solution of hydroxy acid followed by multistep thermal treatment. Physicochemical properties of the modified carbon sorbents were studied using low-temperature nitrogen adsorption, scanning electron microscopy, elemental, thermal and spectrophotometric analyses, nuclear magnetic resonance spectroscopy and viscometry. Modification of the carbon sorbent with oligomers of hydroxy acids is accompanied by the appropriate deterioration of its textural characteristics and substantial increase in the oxygen content. The deposited oligomers of glycolic and lactic acids are distributed locally on the carbon surface. It was shown that the sorbent modified with glycolic acid oligomer was more hydrophilic. It exhibited a higher adsorption capacity with respect to gelatin as compared to the sorbent modified with lactic acid oligomer. Differences were found in the biological activity of modified samples toward pathogenic bacteria Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli, yeast-like fungi of the Candida genus, and bacterial-fungal Staphylococcus aureus + Candida albicans association. The higher biological activity of the modified carbon sorbents in comparison with the initial sample was attributed to the acid–base properties of deposited oligomers and their ability to biodegrade in an aqueous medium.Graphical abstract

Adsorbed natural gas (ANG) storage is a promising solution to the problem of uneven supply and consumption of natural gas. ANG storages are relatively simple, safe and do not require complex infrastructure. The paper investigates the properties of activated carbon of wood origin synthesized by the method of chemical activation, as well as the theoretical capacity and thermodynamic properties of ANG storage facilities equipped with this adsorbent. An original graphical method for calculating the parameters and processes of ANG storage facilities is presented using the example of synthesized active carbon. Various types of ANG storage charging are considered: adiabatic processes of charging with compressed and liquefied gas, isothermal and pseudo-isothermal processes. So adiabatic charging with liquefied gas allows reaching a storage capacity of 150 m3/m3 at a pressure of 3.5 MPa. A number of recommendations were made regarding the choice of the charging type from the standpoint of the ANG storage facility design.

Single-walled carbon nanotube (SWCNT) based materials are considered as one of the most promising adsorbents for adsorption-based technology for methane storage. Molecular dynamic simulations are employed to investigate the assembling of single-walled carbon nanotubes into an array via toluene coordinator-molecules. The smallest number of toluene molecules sufficient to maintain the ASWCNT + nC7H8 supramolecular structure is defined. The potential, kinetic and total energies of the simulated system plotted as a function of toluene molecules are used to evaluate the stability condition for the supramolecular structure. Methane adsorption onto the model ASWCNT + nC7H8 adsorbent is simulated to assess the contributions of toluene molecules to its adsorption capacity. The radial and angular probability density distributions of methane molecules in the ASWCNT + nC7H8 adsorbent reveal the most probable location of adsorbed methane near the SWCNT walls and toluene molecules as centers of adsorption. A SWCNT-based adsorbent is prepared by the saturation with toluene and subsequent two-step regeneration with a slow-rate increase in temperature. The content of toluene of 5wt.% in the adsorbent thus obtained is evaluated from a gain in weight observed at 338 K. Methane adsorption on the initial SWCNT and SWCNT + 5%C7H8 adsorbents is measured at 178 and 273 K up to 101 kPa. A comparison of the initial and differential molar heats of methane adsorption on the initial SWCNT and ASWCNT + nC7H8 adsorbents points to the role of toluene molecules as additional centers of adsorption. We estimate the contribution of toluene molecules to the porosity of the ASWCNT + nC7H8 adsorbent from the methane adsorption data.

Adsorption of methane on three Sichuan Basin shales at 318 K, 338 K, and 358 K has been investigated experimentally. The adsorption equilibrium isotherm data were fitted with Langmuir, DR and DA model. A thermodynamic model on heat of adsorption (Qst), considering the non-ideality of gas and the adsorbed phase specific volume, was developed for adsorption fields of methane and shales. The other thermodynamic properties, included specific heat capacity of adsorbed phase (cp,a), entropy (sa) and enthalpy (ha) of adsorbed phase, were also evaluated on basis of the developed heat of adsorption model. The calculated isosteric heat of adsorption shows a temperature independent feature at lower surface loading while a negative temperature dependence at higher surface loading. Specific heat capacity of adsorbed phase (cpa) values increases with temperature, pressure and adsorption amount. The change of cpa value with temperature are higher at lower pressure and adsorption amount. The entropy and enthalpy of adsorbed phase decreases with the increase of methane adsorption, and the entropy change is larger at lower temperature suggesting lower temperature is conducive to formed ordered arrangement of CH4 molecules.

Alumina catalysts are frequently used in refineries for the hydrotreatment of heavy petroleum fraction that are enriched in asphaltenes. The transport of real and model asphaltenes molecules through powder and alumina’s extrudates treated or not at 150 °C to remove or not surface-adsorbed water was studied. The kinetics and isotherms of adsorption at 298 K were obtained by the solution depletion method. Calorimetric experiments were also investigated. The kinetic is faster on the powder than on the alumina extrudates where the equilibrium is reached after 24 h (against 1 h for the powder) due to mass transfer limitation. The capacity of adsorption of model asphaltenes on untreated powder and extrudates is comparable around 1.1 and 1.2 mg.m− 2 and increases with the heat treatment due to water removal. Both adsorption strength and capacity of real asphaltenes on alumina is lower compared to the model asphaltene molecule which could be explained by the strong interaction between the acidic function of the model molecule and the alumina surface. The calorimetric study in absence of alumina shows the dimerization of model asphaltene molecules. In presence of alumina, the enthalpy of adsorption of model and real asphaltenes on alumina is determined. The enthalpy of adsorption of model asphaltenes on treated powder is higher than on untreated powder meaning that more energetic sites are available (probably due to the release of water-occupied sites) and the curve obtained for treated powder suggests different adsorption sites. The enthalpy of adsorption of model asphaltene is higher for the treated extrudates but these results must be taken carefully because the kinetic of adsorption is very slow (24 h) for extrudates. The effect of flow rate was studied by saturating an extrudate column with model asphaltene molecules. The adsorption increases as the flow rate decreases which could be explained by higher friction in the macropores leading to the release of weakly retained asphaltenes as the flow rate increases or by less intermediate pore blocking by asphaltenes as the flow rate and thus the pressure increases. This study shows that the transport of asphaltenes through porous alumina supports is a complex process depending on many parameters.

This comment seeks to establish a relation between two definitions of the pore volume of a microporous crystalline material. According to the first definition based on the Gurvich rule, the volume of the pores can be estimated from the saturated amount of vapour adsorbed, using the bulk liquid density of adsorbate as the conversion factor. The second definition is based on a purely geometric consideration of the porous space. With argon as the adsorbate and all-silica zeolite structures from the International Zeolite Association (IZA) database as the model adsorbents, we generate adsorption data using Grand Canonical Monte Carlo simulations and structural characteristics of the materials from the Poreblazer PB4.0 software. Under confinement in zeolitic pores, adsorbed argon forms structures very different from the liquid-like configurations. However, the pore volumes of these materials obtained from the Gurvich may deviate positively or negatively from the reference geometric value. Considering simply the geometric features of the materials, such as the pore volume itself or the pore size distribution, it proved to be difficult to anticipate how the volume from the Gurvich rule would deviate from the geometric volume for a particular structure. Overall, volume from the Gurvich rule agrees with the geometric volume within 25% error for 82% of the structures from the IZA database. As an additional outcome of this study, we provide a comprehensive database of textural characteristics and simulated argon adsorption data for all-silica zeolites, which can be used as reference values for the assessment of the quality of the microporous samples of all-silica zeolites in future experimental studies.

The adsorption of chloroxylenol and chlorophene on halloysite-carbon composites was investigated in batch and flow systems. The synthesis of halloysite-carbon composites through two different methods was performed with microcrystalline cellulose as carbon precursor. The obtained halloysite-carbon composites were characterized by SEM/EDS analysis, the low-temperature nitrogen adsorption/desorption methods, and infrared spectrometry (FT-IR). The SEM/EDS analysis and FT-IR spectra confirmed the presence of carbon on the surface of the halloysite. On the basis of the measurement results in the batch system, the two composites with the best adsorption properties for both adsorbates were chosen for measuring the flow system (using the inverse liquid chromatography). Removal efficiency was equal to 92.26 and 81.36%. It was obtained for chloroxylenol on HNT-m 800 and HNT-Zn 500, respectively. For chlorophene, the removal efficiency had the value of 78.79 and 77.87% on HNT-m 800 and HNT-Zn 800, respectively. Adsorption parameters of chloroxylenol and chlorophene were determined with inverse liquid chromatography methods: the adsorption equilibrium constants were determined with the peak division method and the adsorption capacity of the adsorbents was determined with the breakthrough curve method. Maximum adsorption capacity for the adsorption of chloroxylenol on HNT-m 800 was 5.48 mg·g−1 and on HNT-Zn 500 its value was 2.77 mg·g−1. For the adsorption of chlorophene on HNT-m 800 the value was 4.44 mg·g−1 and on HNT-Zn 800–2.5 mg·g−1. Halloysite-carbon composites can be successfully used as effective adsorbents for removing chloroxylenol and chlorophene from solutions in the flow system.

This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of water vapor sorption isotherms at 25 °C on a pelletized nanoporous carbon (BAM-P109, a certified reference material). Thirteen laboratories participated in the study and contributed nine pure water vapor isotherms and four relative humidity isotherms, using nitrogen as the carrier gas. From these data, reference isotherms, along with the 95% uncertainty interval (Uk=2), were determined and are reported in a tabular format.

We have carried out the traditional analysis of a set of dynamic breakthrough experiments on the \(\hbox {CO}_2\)/He system adsorbing onto activated carbon by fitting a 1D dynamic column breakthrough model to the transient experimental profiles. We have quantified the uncertainties in the fitted model parameters using the techniques of Bayesian inference, and have propagated these parametric uncertainties through the dynamic model to assess the robustness of the modelling. We have found significant uncertainties in the outlet mole fraction profile, internal temperature profile and internal adsorption profiles of approximately \(\pm 15\%\). To assess routes to reduce these uncertainties we have applied a global variance-based sensitivity analysis to the dynamic model using the Sobol method. We have found that approximately \(70\%\) of the observed variability in the modelling outputs can be attributed to uncertainties in the adsorption isotherm parameters that describe its temperature dependence. We also make various recommendations for practitioners, using the developed Bayesian statistical tools, regarding the choice of the isotherm model, the choice of the fitting data for the extraction of system specific parameters and the simplification of the wall energy balance.

The cap-removal conditions of chemical vapor deposition-prepared single wall carbon nanotube (SWCNT) bundles were optimized via air oxidation at different temperatures.We determined specific surface areas (SSAs) of the SWCNT oxidized at different temperatures from N2 adsorption isotherms with the aid of the subtracting pore effect (SPE) method enabling evaluation of the SSA of microporous carbons without overestimation. The oxidation of SWCNT at 773 K gave the maximum SSA of 1840 m2 g−1. We chose the oxidation temperature of 773 K for the optimum oxidation for the cap-removal without serious crystallinity damages. The SSAs from the SPE method of the SWCNT bundles before and after oxidation at 773 K almost coincided with the geometrically evaluated SSAs of SWCNT with and without caps, confirming the selective removal of caps from SWCNT through the oxidation at 773 K. TEM and Raman spectroscopic examination guaranteed the well-crystalline state of the SWCNT bundles oxidized at 773 K, as suggested from N2 adsorption measurements.

Natural aggregates from sedimentary rock, like limestone and dolomite, are of a great use in various practical applications. To evaluate their quality, among others, the test of methylene blue adsorption (MB value) using a filter paper is recommended. However, one can consider it as a rough test. In this paper we wished to evaluate its quality by comparison with a more precise spectrophotometric method, i.e., to perform adsorption isotherms of methylene blue from aqueous solutions, as well as determine other parameters characterizing the aggregates. For this purpose, methylene blue adsorption on samples of limestone and dolomite natural aggregates having various grain sizes were studied to assess quality (fine particles content) of the manufactured aggregates. To determine the amount of adsorbed dye two methods were used: the methylene blue stain test and the dye adsorption from its solutions at various concentrations under static conditions. From the linear form of Langmuir adsorption isotherms of methylene blue, the monolayer capacity was determined, and then the specific surface areas of all fractions of aggregates. The structural (N2 adsorption/desorption), textural (SEM/EDS) and crystallographic structure of the aggregates were studied. It was determined that the MB values for 0–2 and MBF for 0–0.125 mm aggregates fractions fulfill the criteria set out in the specifications required for pavement construction. A very good repeatability of the adsorbed amount of methylene blue on the dolomite and limestone aggregates were obtained by these two different methods. These results confirm the reliability of the method blue test used typically in industrial conditions. The measured specific surface areas of limestone and dolomite using N2 adsorption (SBET) are smaller than SMB determined by methylene blue adsorption from aqueous solutions. This is because in aggregates, apart from calcite and dolomite, there is a small admixture of quartz and clay minerals. During N2 adsorption in dry condition, the external surface of the grains is determined, while in the aqueous solution of methylene blue, both the external and inner surfaces of clay minerals are determined.

Two types of modified nanocrystalline cellulose (NCC) were tested for low-concentration SO2 adsorption performance investigation. In this study, NCC was chemically modified with citric acid (CA) and ethylenediamine (EDA) to enhance its potential for SO2 capture. The study reports the successful incorporation of carboxylic acid and amine groups on the surface of cellulose, as shown by XRD, FTIR, TGA, SEM, and EDS analysis. Acid-based titration revealed that 83% of hydroxyl groups of NCC were carboxylate and 92% of supplied carboxyl groups reacted with EDA. The SO2 capture results indicated that EDA-CA-functionalized NCC showed a higher sorption capacity of 1.05 mg-SO2/gsorben at room temperature, atmospheric pressure, and a 20 mL/min flow rate compared to NCC and CA modified cellulose. This suggests that the amine groups in EDA-CA-NCC play a crucial role in adsorbing SO2, while the carboxylic groups in CA-NCC yielded a lower adsorption capacity.