Temperature-dependent Sorption Research Articles

Predicting the solubility of gases, vapors, and supercritical fluids in amorphous polymers from electron density using convolutional neural networks

A twin convolutional neural network is proposed to predict the pressure and temperature-dependent sorption of gases, vapors, and supercritical fluids in amorphous polymers, using spatial electron density distribution.

Sorption study of long-lived 94Nb on laterite: Effects of physicochemical parameters on sorption

Zr–Nb alloy is used as the pressure tube in pressurized heavy water reactors (PHWR). Prolonged neutron irradiation of the pressure tubes leads to the formation of a long-lived radioisotope 94Nb. Thus, the discharged pressure tubes possess huge 94Nb activity which persists for a prolonged period.If these discharged pressure tubes come in contact with ground water, 94Nb isotope may leach and migrate and this can lead to a long-term radiological impact in the environment.In the present study, we have explored the capability of laterite as a filler material for the containment and retarding the migration of 94Nb. In this regard, detailed characterization of the laterite soil was carried out using energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), fourier transform infra-red spectrometry (FTIR), total cation exchange capacity determination, zeta potential measurement and thermogravimetric analysis (TGA). The sorption study of 94Nb on laterite was carried and the effects of different physico-chemical parameters like pH, ionic strength, temperature and equilibration time were evaluated. Ionic strength, temperature and time dependent sorption studies assist to explore the probable sorption mechanism of 94Nb on laterite, which helps in understanding the migration behaviour of 94Nb in natural aquatic environment. This study suggests that laterite is a promising material in containment of 94Nb isotope owing to its good cation exchange behaviour in the acidic medium and ability to form surface complex in the neutral medium.

Tetranuclear CuII Cluster as the Ten Node Building Unit for the Construction of a Metal-Organic Framework for Efficient C2 H2 /CO2 Separation.

Rational design of high nuclear copper cluster-based metal-organic frameworks has not been established yet. Herein, we report a novel MOF (FJU-112) with the ten-connected tetranuclear copper cluster [Cu4 (PO3 )2 (μ2 -H2 O)2 (CO2 )4 ] as the node which was capped by the deprotonated organic ligand of H4 L (3,5-Dicarboxyphenylphosphonic acid). With BPE (1,2-Bis(4-pyridyl)ethane) as the pore partitioner, the pore spaces in the structure of FJU-112 were divided into several smaller cages and smaller windows for efficient gas adsorption and separation. FJU-112 exhibits a high separation performance for the C2 H2 /CO2 separation, which were established by the temperature-dependent sorption isotherms and further confirmed by the lab-scale dynamic breakthrough experiments. The grand canonical Monte Carlo simulations (GCMC) studies show that its high C2 H2 /CO2 separation performance is contributed to the strong π-complexation interactions between the C2 H2 molecules and framework pore surfaces, leading to its more C2 H2 uptakes over CO2 molecules.

Quantification of Temperature-Dependent Sorption Isotherms in Shale Gas Reservoirs: Experiment and Theory

Summary A critical component of natural gas in organic-rich shales is adsorbed gas within organic matter. Quantification of adsorbed gas is essential for reliable estimates of gas-in-place in shale reservoirs. However, conventional high-pressure adsorption measurements for coal using the volumetric method are prone to error when applied to characterize sorption isotherm in shale gas systems due to limited adsorption capacity and finer pores of shale matrix. Innovative laboratory apparatus and measurement procedures have been developed to accurately determine the relatively small amount of adsorbed gas in a Marcellus shale sample. The custom-built volumetric apparatus is a differential unit composed of two identical single-sided units (one blank and one adsorption side) connected with a differential pressure transducer. The scale of the differential pressure transducer is ±50 psi, a hundred-fold smaller than the absolute pressure transducer measuring to 5,000 psi, leading to a significant increase in the accuracy of adsorption measurement. Methane adsorption isotherms on Marcellus shale are measured at 303, 313, 323, and 333 K with pressure up to 3,000 psi. In addition, a fugacity-based Dubinin-Astakhov (D-A) isotherm is implemented to correct for the nonideality and to predict the temperature dependence of supercritical gas sorption. The Marcellus shale studied generally displays linear correlations between adsorption capacity and pressure over the range of temperature and pressure investigated, indicating the presence of a solute gas component. It is noted that the condensed-phase gas storage exists as the adsorbed gas on the shale surface and dissolved gas in kerogen, where the solute gas amount is proportional to the partial pressure of that gas above the solution. One of the major findings of this work is the experimental observation of the contribution of dissolved gas to total gas storage. With adsorption potential being modeled by a temperature-dependence expression, the D-A isotherm can successfully describe supercritical gas sorption for shale at multiple temperatures. Adsorption capacity significantly decreases with temperature attributed to the isosteric heat of adsorption. Lastly, the broad applicability of the proposed fugacity-based D-A model is also tested for adsorption data provided in the literature for Woodford, Barnett, and Devonian shale. Overall, the fugacity-based D-A isotherm provides precise representations of the temperature-dependent gas adsorption on shales investigated in this work. The application of the proposed adsorption model allows predicting adsorption data at multiple temperatures based on the adsorption data collected at a single temperature. This study lays the foundation for an accurate evaluation of gas storage in shale.

Pregled modela sorpcionih izotermi

Numerous mathematical models for approximation of sorption data of food and agriculture materials are available in the referent scientific and engineering literature. Depending on the number of parameters included in the model for approximation of moisture sorption data, the models may be one, two, three, four, five or more parametric. Also the sorption models may be included or not the temperature as a parameter into the equation. The objectives of the presented article was a review of one hundred seventy-two sorption no temperature dependent sorption isotherm models which used to for approximation equilibrium moisture data of food materials. For statistics evaluation of those models the equilibrium moisture data of quince were used. The value on coefficient of determination the root mean squared error, the mean relative deviation and graphical evaluation of the residual randomness were the main assessment criterions for statistical evaluation of the sorption isotherms model. Based on the performed statistical analysis it was concluded that the model of Popovski & Mitrevski i.e. M161 has the best statistical performances.

Applicability of ground source heat pumps as a bioremediation-enhancing technology for monoaromatic hydrocarbon contaminants

Geothermal or ground source heat pumps (GSHPs) are among the highest growing renewable energy technologies used for heating and cooling of buildings. However, despite being a well-established technology, their geo-environmental effects such as impact of the heat on the biosphere is still not thoroughly understood. This study uses FEFLOW software, to simulate heat and mass transport of a vertical closed-loop GSHP system. Transient flow and heat transport results for a multiple borehole system are presented which indicate long-term effects on subsurface temperature. Moreover, the impact of temperature change in a contaminated granular porous subsurface during remediation applications is examined. In particular, as subsurface temperatures are elevated due to geothermal heating, sorption will decrease and biodegradation rates will increase. These effects are examined in the context of contaminant transport, to evaluate the possibility of utilizing geothermal heating as a remediation strategy. The results revealed that temperature changes caused by GSHP operation can significantly enhance biodegradation of hydrocarbon contaminants. For instance, elevated subsurface temperature resulted in 97% reduction in benzene total mass, after one year of GSHP operation for a typical office building in Toronto.

Characterization of ZSM-5 monolith as solid sorbent for Ni2+ removal

Solid wastes exhibit excellent prospects in the removal of heavy metals from contaminated water. However, raw solid waste materials usually show mediocre uptake efficiency, it is imperative to functionalize or transform them into new solid waste-based materials. The present work provides a novel technique by utilization of silica fume waste for Ni2+ removal from wastewater. The sorbent was prepared by in-suit conversion of amorphous silica fume based geopolymer into monolithic ZSM-5 via polycondensation and seed-induced hydrothermal treatment process. The adsorption behavior of Ni2+ in aqueous solution onto the as-synthesized monolithic ZSM-5 was investigated. The adsorption experiment data fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic parameters including ΔH, ΔG and ΔS were calculated from the temperature-dependent sorption isotherms. All the results confirmed that the sorption of Ni2+ onto monolithic ZSM-5 was a spontaneously endothermic chemisorption process, demonstrating the removal of Ni2+ from wastewater using monolithic ZSM-5 was feasible. The adsorption capacity of Ni2+ onto monolithic ZSM-5 was 13.22 mg/g at 25 °C, which was a competitive result compared with similar adsorbents and commercial ZSM-5 powders.

Effect of different physico-chemical factors on sorption of Pa(V) on iron oxides

The effects of different physico-chemical parameters on sorption of protactinium (Pa) on three different iron oxides (goethite, hematite and magnetite) were studied. The sorption of Pa(V) on all the three iron oxides was low at pH 1, increased to ~ 90% at neutral pH and then decreased slightly above pH 9. Presence of humic acid increases the sorption of Pa(V) on iron oxides in acidic medium whereas sorption is reduced in basic medium. The classical methods like ionic strength, time and temperature dependent sorption studies have been used for the elucidation of the sorption mechanism of Pa(V) on iron oxides. Physisorption in acidic pH and chemisorption in basic pH are the most probable mechanisms. The study demonstrates that classical method alone can be used for the sorption mechanism investigations in the circumstances where it is difficult to have spectroscopic evidences.

Temperature-dependent sorption models for mass transfer throughout bio-based building materials

Hemp and rape straw concretes are bio-based building materials with excellent hygrothermal behaviour and low environmental impact compared to conventional concretes. Their hygroscopic capacity can improve indoor comfort by regulating temperature and relative humidity levels. This buffering ability can be expressed by sorption curves which correlate moisture content at different relative humiditiy levels. However, sorption isotherms vary according to temperature revealing the importance of taking into account heat transfer in sorption phenomena. Therefore, aiming to accurately model sorption curves considering temperature and hysteresis influence, this study compares four different temperature-dependent models (Poyet, Milly, Staudt and modified GAB) to better describe the hygroscopic behaviour of bio-based materials. Results show that, when compared to experimental values, the modified GAB model exhibited the best statistical agreement. Poyet and Milly remained coherent with empirical results, nevertheless, Staudt’s approach is far from experimental data. The isosteric heat of sorption and the theory of compensation are used to shed a new light on results discrepancy. This work also points out that the robustness of analysis is highly related to the initial parameters of accuracy given by GAB fitting.

Temperature dependence of sorption isotherm of hygroscopic building materials. Part 1: Experimental evidence and modeling

The knowledge of sorption isotherm is of high importance when evaluating the performance and the durability of building envelope. Whereas the influence of hysteresis was often investigated, less attention has been paid to the influence of temperature. In the present paper, a specific experimental protocol is defined to investigate the influence of temperature on relative humidity variations within three building materials (Autoclaved Aerated Concrete, wood fiber insulation and hemp concrete). The measurements are analyzed in terms of a hygrometric coefficient κ [%r.h./°C], defined as the maximal relative humidity amplitude against the maximal temperature amplitude, and are compared to three modeling approaches: temperature dependent sorption model, Kelvin equation and Clausius-Clapeyron equation. Discussions show that the third approach is relevant and that it can be used to evaluate effortless the isosteric heat of sorption and the temperature dependence of the sorption isotherm.

Removal of thorium(IV) from aqueous solutions by natural sepiolite

Abstract Natural sepiolite has been tested as a potential sorbent for the removal of Th(IV) from aqueous solutions by batch technique. Effects of various parameters on the adsorption process have been investigated. Under optimum conditions, Th(IV) was adsorbed with high adsorption efficiency. The results indicated that sorption of Th(IV) on sepiolite was strongly affected by pH values and temperature. The adsorption patterns of thorium on the sepiolite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The thermodynamic data (ΔH°, ΔS°, ΔG°) are calculated from the temperature-dependent sorption isotherms. The results suggest that sorption process of Th(IV) on sepiolite is spontaneous and endothermic.

Kinetic investigations of the steam reforming of methanol over a Pt/In2O3/Al2O3 catalyst in microchannels

A kinetic study of methanol steam reforming over bimetallic Pt/In2O3/Al2O3 catalyst was carried out. The kinetic measurements were performed in a microstructured monolithic reactor with an external recycle free of temperature and concentration gradients. By the help of residence time distribution measurements it could be verified that the reactor showed the behaviour of an ideal continuous stirred tank reactor (CSTR). The absence of external and internal concentration gradients could be proven by corresponding experiments and theoretical diagnostic criteria.The kinetic measurements performed by variation of the reactant inlet partial pressures revealed that in the temperature range from 310°C to 355°C the molar rate of methanol consumption mainly depends on the methanol partial pressure, especially at higher temperatures, whereas there is only minor dependence on the water partial pressure. Carbon dioxide has no inhibiting effect, whereas hydrogen showed a weak inhibiting effect.Two power laws and three Langmuir-Hinshelwood rate equations were created for the modelling of the kinetic data. Power laws could not be fitted to the measured values. Therefore the uses of Langmuir-Hinshelwood rate laws with temperature dependent sorption constants are inevitable for the modelling. The model discrimination revealed that the rate law derived from a mechanism, which assumes the dehydrogenation of an adsorbed methoxy-species as rate determining step, described the measured kinetic data second best. Optimum agreement between observed and predicted molar rates of methanol consumption was obtained when applying a Langmuir-Hinshelwood rate law assuming dissociative methanol and molecular water adsorption on the catalyst surface. Dissociative adsorption of water and methanol at the same active site may be excluded. This leads to a better evaluation of the models that assume molecular water adsorption at the same site where methanol ties or the ones with no participation of water in the rate determining step (RDS) under discrimination.

Combined effects of sorption hysteresis and its temperature dependency on wood materials and building enclosures-part II: Hygrothermal modeling

Hygroscopic materials such as wood and wood based materials have been widely used as insulation and surface moisture buffering materials due to their low thermal conductivity and high moisture capacity. And their hygrothermal performance is mainly dependent on the moisture properties, such as sorption isotherm and water vapor permeability etc. Instead of a univalued function of relative humidity, sorption isotherm of wood materials is not only affected by sorption history, but also temperature dependent. This work is devoted to a better understanding of the effects of temperature dependent sorption hysteresis on moisture transport in wood and wood based materials under ambient temperature and relative humidity variations through experimental investigations and numerical modeling. In part I, the formulated hygrothermal model based on local thermodynamic equilibrium assumption and Frandsen’s hysteresis model are experimentally validated. In this part, the effects of sorption hysteresis and its temperature dependency are investigated under several dynamic conditions through numerical modeling. Hysteresis should be taken into account in determining the moisture buffering capacity, and temperature dependency should be considered to investigate the RH variation in the material when it is subjected to drastic temperature fluctuation. Then heat and moisture transport through a roof assembly under natural climate conditions is further modelled to show the effects of temperature dependent sorption hysteresis in practical applications.

Study on sulfadimethoxine removal from aqueous solutions by hydrous ferric oxides.

Significant concerns have been raised over the presence of antibiotics including sulfadimethoxine (SDMO) in aquatic environments. This study investigated the removal capability and mechanism involved in the removal of SDMO by hydrous ferric oxides (HFO). Results showed that SDMO removal was highly pH and ionic strength dependent. The pseudo-first-order model fitted well the kinetic results, and the value of the calculated activation energy for SDMO adsorption onto HFO was 8.6 kJ mol(-1). Adsorption isotherms at varied temperatures were well described by the Langmuir model. Thermodynamic parameters (change in enthalpy > 0, change in entropy > 0, and change in Gibbs free energy < 0) calculated from the temperature-dependent sorption data revealed spontaneous and endothermic process. The exchange of the surface hydroxyl groups of HFO and the negative anions of SDMO(-) and the electrostatic interaction between the positively charged surface of HFO and the deprotonated imino (-N(-)-) accounted for the uptake of SDMO by HFO.

Effect of Temperature-Dependent Sorption Characteristics on the Hygrothermal Behavior of a Hemp Concrete Building Envelope Submitted to Real Outdoor Conditions

Effect of Temperature-Dependent Sorption Characteristics on the Hygrothermal Behavior of a Hemp Concrete Building Envelope Submitted to Real Outdoor Conditions

A Fickian model for temperature-dependent sorption hysteresis in hygrothermal modeling of wood materials

The sorption isotherm is one of the most important hygric properties for modeling moisture transport in hygroscopic materials. For wood and wood based materials, the equilibrium moisture content within hygroscopic range is a function of temperature and relative humidity as well as its sorption history. The constitutive equations of the existing models in literature, which attempted to take into account temperature dependent sorption hysteresis, are either incomplete or have too many model parameters needed to be experimentally determined. As a result they are not suitable for practical applications in building physics. Therefore, a coupled heat and moisture transport model is formulated based on the classical local thermodynamic equilibrium assumption. Frandsen’s hysteresis model is adopted and implemented in this Fickian model to determine the moisture capacity and thermal moisture capacity, since it avoids the needs to store the entire moisture history. The formulated hygrothermal model is numerically resolved in Modelica by virtue of a combination of storage model and flow model. For hygroscopic material with sorption hysteresis, its water vapor resistance factor has also been recalculated as a univalued function of moisture content instead of relative humidity. With different considerations for the moisture sorption isotherms, the new model provides the possibility of numerical study under different levels depending on the way to consider moisture sorption property. A simple example case is carried out to show the performance of the new model.

Characterization of Fe(III)-saturated montmorillonite and evaluation its sorption behavior for U(VI)

Abstract Radioactive waste is usually sealed in steel canisters surrounded by a layer of compacted clay back-fill, and permanent buried in a deep geological repository. Unavoidably, the radionuclide contaminants can be released from repository and then sorbed onto the waste container corrosion products or the Fe-rich minerals. Herein, we characterized the Fe(III)-saturated montmorillonite (Fe(III)-MMT) by using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET), and found the changes of the surface incorporating Fe(III) and surface micropores. The sorption of U(VI) on Fe(III)-MMT and Na-montmorillonite (Na-MMT) was investigated by batch experiments. The larger surface area and cation exchange capacity, and the existence of Fe(III) (hydr)oxide phases in Fe(III)-MMT contributed greatly to its sorption capacity. In the whole pH range, the sorption of U(VI) on Fe(III)-MMT was higher than on Na-MMT, and the sorption was strongly depended on pH and ionic strength. The sorption isotherms were simulated well by the Langmuir and Freundlich models. The thermodynamic parameters (ΔH, ΔS and ΔG) calculated from the temperature dependent sorption isotherms indicated that the sorption of U(VI) on Fe(III)-MMT was an endothermic and spontaneous process. The observations suggest that the interactions between U(VI) and Fe(III)-MMT are important in controlling U(VI) retention. The phenomena need to be considered in risk assessment and reactive transport modeling.

Sepiolite functionalized with N-[3-(trimethoxysilyl)propyl]-ethylenediamine triacetic acid trisodium salt. Part II: Sorption of Ni2+ from aqueous solutions

sorption of Ni2+ on the sepiolite functionalized by covalent grafting of N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, MSEAS, was studied in batch experiments as a function of the initial metal concentration, the equilibration time, pH value, and temperature. The modification of sepiolite resulted in an enhanced Ni2+ retention with a capacity of 0.261 mmol/g at 298 K. The retention of Ni2+ ions occurred dominantly by specific sorption and exchange of Mg2+ ions from the sepiolite structure. The sorption process followed pseudo-second-order kinetics. The sorption equilibrium results were best described by the non-linear form of the Langmuir Sorption Equation. The values of the thermodynamic parameters (enthalpy, free energy and entropy) were calculated from temperature dependent sorption isotherms and these values showed that the sorption of Ni2+ onto modified sepiolite was endothermic.

Synthesis of magnetic polyaniline/graphene oxide composites and their application in the efficient removal of Cu(II) from aqueous solutions

The magnetic polyaniline/graphene oxide (MPANI/GO) composites were synthesized by using aniline in the presence of GO. The sorption of Cu(II) on the MPANI/GO composites were studied as a function of pH, contact time, ionic strength, foreign cation and anion ions, and the results showed that Cu(II) sorption was strongly dependent on pH, and independent of ionic strength. The sorption of Cu(II) was mainly domonated by outer-sphere surface complexation at low pH, and by inner-sphere surface complexation at high pH. The thermodynamic parameters calculated from temperature-dependent sorption isotherms indicated that the sorption process was endothermic and spontaneous. The MPANI/GO composites were effective materials for the removal of Cu(II) from large volumes of aqueous solutions and could be separated by using magnetic separation method in the practical applications.

Effect of Temperature-dependent Sorption Characteristics on The Hygrothermal Behavior of Hemp Concrete

Hemp concrete has been used more and more in building construction because hemp is a renewable plant, recyclable and does not degrade within time. Up to now, many simulation tools use the sorption isotherms that describe the relationship between relative humidity of air and the moisture content to predict the humidity in porous materials. However, the sorption capacity of material depends on temperature. The objective of this paper is to study the impact of the temperature dependency of the sorption curves on the hygrothermal behavior of a hemp concrete building envelope. Mathematical models to describe the coupled heat and mass transfer in porous materials are presented and validated against experimental data at the wall scale. The results show that taking the influence of temperature on the sorption characteristics into account is necessary for better prediction of the hygrothermal behavior of a hemp concrete wall.