Sorption Isotherm Measurements Research Articles

Water-Enhanced Direct Air Capture of Carbon Dioxide in Metal-Organic Frameworks.

We have developed two series of amine-functionalized zirconium (Zr) metal-organic framework-808 (MOF-808), which were produced by postsynthetic modifications to have either amino acids coordinated to Zr ions (MOF-808-AAs) or polyamines covalently bound to the chloro-functionalized structure (MOF-808-PAs). These MOF variants were comprehensively characterized by liquid-state 1H nuclear magnetic resonance (NMR) measurements and potentiometric acid-base titration to determine the amounts of amines, energy-dispersive X-ray spectroscopy to assess the extent of covalent substitution by polyamines, powder X-ray diffraction analysis to verify the maintenance of the MOF crystallinity and structure after postsynthetic modifications, nitrogen sorption isotherm measurements to confirm retention of the porosity, and water sorption isotherm measurements to find the water uptake in the pores of each member of the series. Evaluation and testing of these compounds in direct air capture (DAC) of CO2 showed improved CO2 capture performance for the functionalized forms, especially under humid conditions: In dry conditions, the l-lysine- and tris(3-aminopropyl)amine-functionalized variants, termed as MOF-808-Lys and MOF-808-TAPA, exhibited the highest CO2 uptakes at 400 ppm, measuring 0.612 and 0.498 mmol g-1, and further capacity enhancement was achieved by introducing 50% relative humidity, resulting in remarkable uptakes of 1.205 and 0.872 mmol g-1 corresponding to 97 and 75% increase compared to the dry uptakes, respectively. The mechanism underlying the enhanced uptake efficiency was revealed by 13C solid-state NMR and temperature-programmed desorption measurements, indicating the formation of bicarbonate species, and therefore a stoichiometry of 1:1 CO2 to each amine site.

Multi-scale analysis of the effects of hysteresis on the hydrothermal behaviour of bio-based materials: Application to hemp concrete

Experimental measurements of sorption isotherms show a difference between the water contents in the adsorption phase and the desorption one. This is mainly due to the hysteresis phenomenon. Not considering this phenomenon in hygrothermal behaviour models impacts the reliability of the latter. In this paper, we have studied the effects of hysteresis on the hygrothermal behaviour at the building scale. For this purpose, a new implementation method of a hysteresis model was proposed and validated at the material and wall scales using a bi-climatic chamber which controlled the indoor and outdoor climate conditions. Then, the effect of the hysteresis phenomenon at the building scale was evaluated following a COMSOL/TRNSYS co-simulation approach to consider the gains and losses in the hydric fluxes going through walls. The results showed significant differences in terms of the relative humidity of the living environment. However, no difference was noticed in the temperature variations. On the other hand, the total heat fluxes were also affected by the hysteresis phenomenon due to latent heat parts, that were driven by variations in relative humidity. The maximum gain and loss discrepancies (with and without hysteresis) in total heat fluxes of 1121 kJ/h and 1086 kJ/h, respectively, were obtained during the first week of February (winter period). The results also revealed that these discrepancies are sensitive to the number of persons in the living environment.

Measured Sorption Isotherms for Bakken Petroleum System Shales Using Carbon Dioxide and Produced Gas Hydrocarbons at 110 °C and Pressures up to 34.5 MPa

Measured Sorption Isotherms for Bakken Petroleum System Shales Using Carbon Dioxide and Produced Gas Hydrocarbons at 110 °C and Pressures up to 34.5 MPa

Reference isotherms for water vapor sorption on nanoporous carbon: results of an interlaboratory study

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.

Investigation of methane mass transfer and sorption in Marcellus shale under variable net-stress

Natural gas in shale exists as free and adsorbed gas, subject to prevailing pore pressures and stress conditions. Accordingly, to accurately estimate/predict the shale gas recovery potential, a central requirement is to represent gas transport and sorption behavior under varying stress conditions. The objective of this work is to facilitate the interpretation of laboratory-scale experiments, at relevant conditions, in an attempt to bridge the gap in scales between laboratory- and field-scale observations.We have conducted a series of high-pressure experiments on a full-diameter core sample from the Marcellus shale. These include gas loading (pressure-decay) and depletion (production) experiments with pure methane (CH4) at variable stress conditions to characterize transport and sorption behavior under reservoir-relevant conditions. We have formulated and applied a novel integral model for mass transfer and storage in multi-porosity shale systems that allows us to effectively investigate transport and sorption phenomena: We delineate gas transport by interpreting helium (He) pressure-decay experiments and demonstrate how to use the information gained to calculate the relevant transport coefficients of CH4 and other gases. A separate measurement of the CH4 sorption isotherm on a smaller sample (a shale cube) was interpreted and combined with the transport description to predict the production behavior of CH4 from the experiments with the full-diameter core.Our experiments demonstrate that the representation of sorption hysteresis is crucial for predicting and guiding shale gas production: At the end of both gas production experiments, approximately 20% of the initial gas in place remained in the core. Without accounting for sorption hysteresis, our modeling demonstrates that the CH4 production could be overestimated by 10%. We demonstrate that our integral, triple-porosity model provides an effective approach for the interpretation and prediction of gas transport and sorption behavior during loading and production experiments on shale cores under variable net-stress conditions.In summary, our work combines measurements and modeling of mass transfer and sorption in shales at different scales to validate a characterization approach that facilitates an improved understanding of shale gas production. Furthermore, the triple-porosity model utilized in our work defines a potential pathway for the translation of laboratory-scale experimentation to larger-scale applications.

Sorption isotherm measurements for porous materials: A new hygroscopic method

The water sorption of materials can significantly affect their durability. While a wide range of techniques has been already introduced and implemented to measure the sorption behavior of materials, obtaining high-resolution data to describe the water sorption isotherm is still a challenging task. This is especially the case for materials with a complex sorption behavior such as concrete for which the pore structure is very complicated. The level of complexity increases when chloride is present in such structures. In this study, a hygroscopic technique is introduced to measure the sorption behavior of porous materials. By this technique, the sorption isotherm can be obtained by injecting water with a high level of control into a controlled environment where a sample is positioned. The amount of water can be added in steps resulting in high-resolution data for the sorption properties of the sample. The technique is evaluated for two porous materials: Portland cement mortar and sand-lime brick. The results are extensively compared with similar measured data available in the literature. In addition, the performance of the technique is evaluated for porous materials with initial chloride content. The results show that the present technique allows for obtaining high-resolution data in desirable ranges that is essential for materials with complicated pore structures.

Understanding surface complexation of antimony on Mg(OH)2: Insights from first-principles molecular dynamics

Sorption processes at the mineral–water interface are of great importance in dominating the fate and availability of metalloid contaminants in natural environment. Aiming at a thorough understanding of the complexation of antimony (Sb) on metal hydroxide, we conducted first-principles molecular dynamic (FPMD) simulations and batch adsorption experiments to elucidate the quantitative mechanism of Sb complexation on Mg(OH)2. Batch experiments showed the sorption of Sb(III) is nearly pH-independent, while increasing pH markedly weakened Sb(V) sorption; the measured sorption isotherm curves were well fitted by Langmuir model. Subsequently, molecular-level mechanism of Sb(V)/Sb(III) on brucite basal and edge surfaces were revealed by FPMD, including microscopic surface reactive sites, local complexing structures and coordination geometries, and complexing free energies. Results showed that Sb(III)/Sb(V) can form outer-sphere complexation on basal surface by hydrogen bonding. On edge surface, Sb(III)/Sb(V) formed stable inner-sphere mononuclear monodentate and binuclear bidentate complexes. The calculated free energies indicated that the binuclear bidentate complexing was more favorable than monodentate structure, and the complexation of Sb(III) was more stable than Sb(V). Accordingly, reaction pathway of the ligand exchange and thermodynamic stability of the different inner-sphere complexes were clarified. This study provides theoretical basis for evaluating the environmental risk of Sb and improving the engineering efficiency of Sb-contaminated water management.

Sorption and Gas Transport Characteristics of Polyimides Based on a Mixture of Diethyl Toluene Diamine Isomers

The transport of oxygen, nitrogen, and hydrocarbons C1–C4 in polyimides based on 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and biphenyl-3,3',4,4'-tetracarboxylic acid dianhydride (BPDA) and diethyl toluene diamine (DETDA) has been studied. The dependences of the diffusion coefficient on the diffusant effective diameter and the solubility coefficients on the Lennard–Jones potential of pair interaction have been considered. It is shown that the diffusion coefficients of butane are out of the linear dependence of the logarithm of the diffusion coefficient on the square of the effective diameter of the diffusant, which may indicate the plasticization of polymers with butane at a pressure of 1 atm. The permeability of mixtures of gases O2–N2 (29 : 71 v/v) and CO2–CH4 (62 : 38 v/v) has been studied. There are no significant differences in the gas separation parameters in comparison with the experiment for individual gases; however, for a mixture of CO2–CH4, a slight increase in the separation factor has been found as compared to the ideal selectivity. The data on the measurement of sorption isotherms and solubility coefficients O2, N2, and CH4 are also presented in the article. Gas solubility coefficients have been found to be close to the values obtained indirectly as P/D.

Comprehensive Multi-compartment Sampling for Quantification of Long-Term Accumulation of PAHs in Soils.

Long-term accumulation in the soils of ubiquitous organic pollutants such as many polycyclic aromatic hydrocarbons (PAHs) depends on deposition from the atmosphere, revolatilization, leaching, and degradation processes such as photolysis and biodegradation. Quantifying the phase distribution and fluxes of these compounds across environmental compartments is thus crucial to understand the long-term contaminant fate. The gas-phase exchange between soil and atmosphere follows chemical fugacity gradients that can be approximated by gas-phase concentrations, yet which are difficult to measure directly. Thus, passive sampling, measured sorption isotherms, or empirical relationships to estimate sorption distribution have been combined in this study to determine aqueous (or gas) phase concentrations from measured bulk concentrations in soil solids. All these methods have their strengths and weaknesses but agree within 1 order of magnitude except for ex situ passive samplers employed in soil slurries, which estimated much lower concentrations in soil water and gas likely due to experimental artifacts. In field measurements, PAH concentrations determined in the atmosphere show a pronounced seasonality with some revolatilization during summer and gaseous deposition during winter, but overall dry deposition dominates annual mean fluxes. The characteristic patterns of PAHs in the different phases (gas phase, atmospheric passive samplers, bulk deposition, and soil solids) confirm the expected compound-specific distribution pattern and behavior. Since revolatilization fluxes in summer are only minor and wet and dry deposition is ongoing, our results clearly show that the PAH loads in topsoils will continue to increase.

Detailed investigation of capillary active insulation materials by 1H nuclear magnetic resonance (NMR) and thermogravimetric drying

Capillary active interior insulation materials are an important and innovative approach to minimize energy losses of historical buildings. In an experimental setup, we investigate the development of moisture profiles under realistic boundary conditions to determine the liquid moisture conductivity for two different interior insulation materials. The moisture profiles were determined by destructive sample cutting with subsequent thermogravimetric drying as well as directly measured by the non-destructive method NMR, which has a higher spatial resolution and even enables repetitive measurements during the course of the experiments. We observed that the moisture profiles obtained from both methods showed good agreement, when compared at the low spatial resolution of sample cutting. This raises confidence in the method of simple mechanical sample cutting. In the next step, the liquid moisture conductivity was calculated using an inverse modelling approach based on both measured moisture profiles separately. Then, we compared the pore-size distributions of the investigated samples based on NMR T2-relaxation-time distributions, mercury intrusion porosimetry and indirect determination from pressure plate and sorption isotherm measurements. Moreover, the measured T2-relaxation-time distributions across the sample depth may give further insight into the saturation degree of the different pore sizes.

Sorption mechanism of Fe(II) on illite: Sorption and modelling

Different countries consider clay formations as potential host rocks for a deep geological disposal of radioactive waste. Minor amounts of Fe(II), which is an important reducing agent in geochemical processes, are typically present in illite, which is a one of the major clay minerals present in different argillaceous rocks. On other hand, the corrosion of nuclear waste casks may act as sources of Fe(II) over time. The presence of Fe(II) in clay minerals may control the behavior of redox sensitive radionuclides such as 99Tc, 75Se and U, whose sorption, solubility and migration are largely affected by their redox state, which is affected by the redox potential in the environment. Thus, a quantitative description of Fe(II) sorption on clay minerals such as illite, is important to understand subsequent reactions with redox sensitive radionuclides. In this study, the sorption of Fe(II) on illite was investigated in batch experiments, including sorption edge and sorption isotherms measurements under anoxic condition. A 2 SPNE SC/CE (2 sites protolysis non-electrostatic surface complex/cation exchange) sorption model extended to account for the surface oxidation of sorbed Fe(II) was used to model the sorption data with geochemical modelling code PHREEQC. Three models (A, B, C) with increasing level of complexity were tested. The model A, in which only Fe(II) interact with illite, fit the experimental data not satisfactorily. This model was modified to include oxidation of surface complexes (Model B) and precipitation of iron bearing phases (Model C). The modified models showed that most of the sorbed Fe(II) was oxidized at pH below 6.5. At pH above 6.5, the oxidized surface complexes either react with water forming surface iron hydroxides or precipitate as hematite, although presence of these could not be confirmed by X-ray diffraction measurements. These sorption processes could be used to couple with redox sensitive radionuclides in future reactive transport research.

Hygric deformation of hardened cement paste with limestone-rich cements under cyclic ad- and desorption

Substitution of Portland cement clinker by limestone powder can significantly reduce the environmental impact of cement and concrete. At the same time, shrinkage will decrease. Within this study, the shrinkage behavior was analyzed on cement pastes made with limestone-rich cements during cyclic ad- and desorption. With an increasing limestone volume, a higher ratio of irreversible shrinkage was observed. A high influence of the clay content of the limestone on the ad- and desorption behavior of limestone-rich cements was revealed, notwithstanding of the minor influence on the pore structure. Water vapor sorption isotherm measurements showed, that the pores coarsened by first drying and cannot be refilled totally later at 95 %RH. Mercury intrusion porosimetry and helium pycnometry indicated a higher proportion of meso- and macropores by increasing limestone volume at constant w/c-ratio. Finally, an analytical prediction model is presented to predict the reversible shrinkage strain of cement pastes made with limestone-rich cements.

Bio-templated synthesis of porous silica nano adsorbents to wastewater treatment inspired by a circular economy

Water is an indispensable substance in human life activities. However, due to industrial discharge problems, water resources are polluted, so there is an urgent need for material and technology for wastewater treatment. This paper presents an innovative synthesis of porous silica microspheres (PSM) from a biomass template material (fish skin collagen) to treat protein from wastewater. The collagen from the biomass template was rich in amino, carboxyl, and hydroxyl groups that effectively controlled the hydrolysis rate of tetraethyl orthosilicate (TEOS) and promoted the synthesis of structured PSM. X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), nitrogen sorption isotherms measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the chemical composition, crystalline structure, and pore architecture of the synthesized PSM. The characterization results confirmed that the PSM were spherical with the microporous and mesoporous structure in shape and approximately 400 nm in size. Moreover, the pore size could be tuned by addition of mesitylene (TMB). The large number of silicon hydroxyl groups on the PSM surface effectively bound proteins in wastewater and greatly improved the overall absorption rate. The PSM adsorption capacity for lysozyme (LZ) was 49.5 mg/g, and the adsorption behavior was well described by a pseudo-second-order kinetic model and the Langmuir model. Most importantly, the PSM effectively removed protein from actual industrial wastewater, thereby realizing a high value-added utilization of wastewater pollutants.

Implication of cation-bridging interaction contribution to sorption of perfluoroalkyl carboxylic acids by soils

Sorption of four perfluoroalkyl carboxylic acids (PFCAs) including perfluoropentanoic acid, perfluoroheptanoic acid, perfluorodecanoic acid, and perfluorododecanoic acid by three soils with cation exchange sites occupied by K+, Ca2+, or Fe3+ was measured using the batch equilibration method. We hypothesize that partitioning in soil organic matters (SOM) is the primarily operative mechanism for PFCA sorption by K+-soils, and sorption by Ca2+- or Fe3+-soils could be enhanced via cation-bridging interaction. The measured sorption isotherms for all four PFCAs by soils were linear within the aqueous concentration between 0 and 60 μg/L, and the distribution coefficients ranged between 14.8 and 173 L/kg. Long-chain PFCAs manifested greater sorption by the soils with higher SOM content. Compared to sorption by K+-soils, sorption of PFCAs by Ca2+- and Fe3+-soils increased by 19.9–90.2% and 38.5–219%, respectively. The relative contributions of cation-bridging interaction to the overall PFCA sorption were estimated to be 16.6–48.7% for Ca2+-soils and 27.8–67.7% for Fe3+-soils. These results demonstrate that multivalent exchangeable cations could play an important role, yet previously ignored, in controlling sorption and transport of PFCAs in soils.

Evaporation Process in Porous Silicon: Cavitation vs Pore Blocking.

We measured sorption isotherms for helium and nitrogen in wide temperature ranges and for a series of porous silicon samples, both native samples and samples with reduced pore mouth, so that the pores have an ink-bottle shape. Combining volumetric measurements and sensitive optical techniques, we show that, at a high temperature, homogeneous cavitation is the relevant evaporation mechanism for all samples. At a low temperature, the evaporation is controlled by meniscus recession, the detailed mechanism being dependent on the pore length and mouth reduction. Native samples and samples with ink-bottle pores shorter than 1 μm behave as an array of independent pores. In contrast, samples with long ink-bottle pores exhibit long-range correlations between pores. In this latter case, evaporation takes place by a collective percolation process and not by heterogeneous cavitation as previously proposed. The variety of evaporation mechanisms points to porous silicon being an anisotropic three-dimensional pore network rather than an array of straight independent pores.

Effect of hemp content and clay stabilization on hygric and thermal properties of hemp-clay composites

The objective of this paper is to investigate the effect of clay stabilization and hemp content on hygric and thermal performances. This experimental study is based on the measurement of sorption isotherm, moisture buffer value and thermal properties. The effect of water content on thermal conductivity is also investigated. The results show that Hemp Clay Composites (HCC) and Hemp Stabilized Clay Composites (HSCC) are hygroscopic and moisture buffering materials. The correlations between hemp content and water content are identified for sorption curves. An innovative analysis of the contribution of hemp and binder to water sorption is performed. The moisture buffer values classify the designed composites as excellent hygric regulators according to the Nordtest classification. The thermal conductivity ranges from 0.089 to 0.120 W/(m.K) at dry state, making them suitable for distributed insulation. The thermal conductivity increases linearly with density, for the two binders investigated in this study. Besides, the thermal conductivity increases linearly with water content too. Finally, this study underlines that the designed composites show high hygrothermal qualities.

Effects of Surface Oxygen-Containing Groups of the Flowerlike Carbon Nanosheets on Palladium Dispersion, Catalytic Activity and Stability in Hydrogenolytic Debenzylation of Tetraacetyldibenzylhexaazaisowurtzitane

The influence of the surface chemical properties of the carbon support on the Pd dispersion, activity and stability of Pd(OH)2/C catalyst for the hydrogenolytic debenzylation of tetraacetyldibenzylhexaazaisowurtzitane (TADB) was studied in detail. The flowerlike nanosheet carbon material (NSC) was chosen as the pristine support, meanwhile chemical oxidation with nitric acid and physical calcination at 600 °C treatments were used to modify its surface properties, which were denoted as NSCox-2 (treated with 20 wt% HNO3) and NSC-600, respectively. The three carbon supports and the corresponding catalysts of Pd/NSC, Pd/NSC-600, and Pd/NSCox-2 were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen sorption isotherm measurement (BET), powder X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectra (XPS), temperature-programmed desorption (TPD), temperature-programmed reduction (H2-TPR), thermogravimetric analysis (TG), and element analysis. The debenzylation activities of Pd/NSC, Pd/NSC-600, and Pd/NSCox-2, as well as the three catalysts after pre-reduction treatment were also evaluated. It was found that the activity and stability of the Pd(OH)2/C catalysts in the debenzylation reaction highly depended on the content of surface oxygen-containing groups of the carbon support.

Green synthesis for novel sorbent of sand coated with (Ca/Al)-layered double hydroxide for the removal of toxic dye from aqueous environment

The novel point of this study is utilization of alum as a cheap compound and cement kiln dust by-product waste resulted from cement industry in the production of layered double hydroxide (LDH) of calcium and aluminum. The gel-solution of this compound was identified by X-ray diffraction (XRD) analysis and immobilized on the sand surfaces to create new sorbent named “sand coated with (Ca/Al)-LDH”. To obtain the highest adsorption capacity for prepared sorbent-Congo red dye interaction, the synthesis parameters were: pH 8, (Ca/Al) molar ratio 2 and dosage of sand 1 g/100 mL. Batch and continuous studies demonstrated that the prepared material was an effective and efficient sorbent for the removal of Congo red dye from simulated wastewater. For initial dye concentration of 50 mg/L, more than 90% of this dye was removed in the batch tests under initial pH-7, time-60 min, sorbent dosage-0.2 g/50 mL and speed-200 rpm with maximum adsorption capacity of 60.64 mg/g. Sorption isotherm and kinetic measurements have formulated in precision manner by Langmuir and pseudo second-order models, respectively and this means that the dye removed by chemisorption. Also, characterization analyses signified that the new nanoparticles precipitated on the sand have significant participation in the supporting of dye sorption. Finally, the longevity of prepared sorbent in packed column increased dramatically with decreasing of flow rate and inlet concentration of contaminant as well as increasing of sorbent mass. Measured breakthrough curves were well simulated by numerical modeling for solute transport equation solved by COMSOL package.

Polymorphism of 2D Imine Covalent Organic Frameworks

AbstractWe designed and synthesized A2B2 type tetraphenyl benzene monomers (p‐, m‐, and o‐TetPB) which have the para‐, meta, and ortho‐substituted isomeric structures, for the direct construction of isomeric frameworks. Interestingly, both kagome (kgm) and monoclinic square (sql) framework isomers are produced from either p‐TetPB (C2h symmetry) or m‐TetPB (C2v symmetry) by changing reaction solvents, while their isomeric structures are characterized by X‐ray diffraction, computational simulation, microscopy, and sorption isotherm measurements. Only sql frameworks was formed for o‐TetPB (C2v symmetry), irrespective of reaction solvents. These results disclose a unique feature in the framework structural formation, that is, the geometry of monomers directs and dominates the lattice growth process while the solvent plays a role in the perturbation of chain growth pattern. The isomeric frameworks exhibit highly selective adsorption of vitamin B12 owing to pore shape and size differences.

Polymorphism of 2D Imine Covalent Organic Frameworks.

We designed and synthesized A2 B2 type tetraphenyl benzene monomers (p-, m-, and o-TetPB) which have the para-, meta, and ortho-substituted isomeric structures, for the direct construction of isomeric frameworks. Interestingly, both kagome (kgm) and monoclinic square (sql) framework isomers are produced from either p-TetPB (C2h symmetry) or m-TetPB (C2v symmetry) by changing reaction solvents, while their isomeric structures are characterized by X-ray diffraction, computational simulation, microscopy, and sorption isotherm measurements. Only sql frameworks was formed for o-TetPB (C2v symmetry), irrespective of reaction solvents. These results disclose a unique feature in the framework structural formation, that is, the geometry of monomers directs and dominates the lattice growth process while the solvent plays a role in the perturbation of chain growth pattern. The isomeric frameworks exhibit highly selective adsorption of vitamin B12 owing to pore shape and size differences.