Desorption Kinetics Research Articles

New insights on antimony removal and recovery from water and wastewater using iron-coated cork granulates: Desorption on batch and fixed-bed column systems

This work investigated Sb adsorption–desorption using iron-coated cork granulates (ICG) in both batch and continuous modes to evaluate the materiaĺs adsorption and regeneration performance, as well as the possibility of antimony recovery. A fixed-bed column filled with ICG, demonstrated maximum adsorption capacities of 13 ± 2 mg g−1 and 10 ± 1 mg g−1 for Sb(III) and Sb(V), respectively, at pH 3. ICG was able to remove Sb within the WHO guideline of 20 μg/L at pH 6. Among the different classes of eluents tested for Sb(V) desorption, the acids achieved the highest desorption rates − 81 ± 9 % and 66 ± 8 % for HCl 1 M and ascorbic acid 0.1 M, respectively. The desorption kinetics showed that HCl 1 M reached equilibrium in 4 h, but ascorbic acid 0.1 M took 16 h. This work presents an ecological emerging solution for antimony removal and recovery from water and wastewater.

Potassium adsorption capacity and desorption kinetics in soils of Qenberenaweti sub-watershed, central highlands of Ethiopia

Determining the supply and uptake of K nutrient and the dynamic equilibrium (adsorption-desorption) reactions among the K forms in the soils are not commonly addressed in the highlands of Ethiopia. A study was therefore initiated to determine the adsorption capacity of the exchangeable K and the release kinetics of the non-exchangeable K in the soils of the Qenberenaweti Sub-watershed. Twelve disturbed surface (0–20 cm) soil sub-samples were collected from every farmland which was representative of each pre-identified soil type (Vertic Cambisols, Pellic Vertisols, Pisoplinthic Luvisols, Relictistagnic Cambisols, Pisoplinthic Cambisols, and Plinthofractic Cambisols). A composite sample was made in duplicate for the determination of K adsorption capacity and desorption kinetics per soil type. The mean maximum (69.47 ± 4.31 %) and minimum (56.16 ± 6.04 %) K adsorption rates were obtained from the Plinthofractic Cambisols and Vertic Cambisols, respectively. Among the tested isotherm models, the goodness of the Freundlich was better fit the data of all experimental soils; hence, a modified equation of this model (qe = aCeb/a) could be used to describe the theoretical doses of K fertilizers required to develop K levels in soil solutions. The highest constant K releases from the Plinthofractic Cambisols (47 mg kg−1), Pisiopllintic Cambisols (46 mg kg−1), and Pisoplinthic Luvisols (44 mg kg−1) were attained at the 9th extraction. In comparison, it was noticed at the 7th and 11th extractions of the Relictistagnic Cambisols (45 mg kg−1) and both Pellic Vertisols (48 mg kg−1) and Vertic Cambisols (42 mg kg−1), respectively. The equation of power function was the best to successfully describe the released K+ from all the experimental soils. Eventually, determining the adsorption capacity and release kinetics of K at a site-specific level helps to know the relative potential of the soils to supply K and also plan for an effective K fertilization strategy.

Improved dehydrogenation performance of LiAlH4 doped with BaMnO3

Due to its high gravimetric capacity of hydrogen (10.5 wt%), LiAlH4 has been regarded as a promising material for solid-state hydrogen storage material for onboard usage. However, high decomposition temperature, poor kinetics and irreversibility retard its application. To counter this problem, various weight percentages of BaMnO3 are introduced into the LiAlH4 system as an additive in this work. As a result, the starting hydrogen release of LiAlH4 was reduced to 109−115 °C and the second desorption temperature occurred at around 134−158 °C, much lower than pure LiAlH4. The isothermal desorption kinetics also proved that faster desorption kinetics can be observed at 90 °C for 80 min. About 2.00−2.60 wt% of H2 could be desorbed by the composite, whereas only <1.00 wt% of H2 was desorbed by undoped LiAlH4. Additionally, adding BaMnO3 reduced the activation energies by 30 kJ/mol for the first stages and 34 kJ/mol for the second stages. Based on the X-ray diffraction result, the active species formed of MnO2 and Ba or Ba−containing materials are believed to be responsible for the noticeable enhancement in the desorption properties of LiAlH4.

Experimental and numerical study of temperature evolution and hydrogen desorption process on an amorphous alloy Mg50Ni50

In the present study, we explored the temperature evolution and hydrogen desorption properties of the Mg50Ni50 alloy through both numerical simulation and experimental analyses. Desorption kinetics characterization was carried out using the volumetric method, specifically employing a Sievert's-type apparatus to investigate solid-gas reactions. The experiments covered a temperature range from 313 K to 353 K, with an initial hydrogen pressure of 12 bar. Simultaneously, a mathematical approach was employed to numerically investigate the temperature evolution within the hydride bed. Using COMSOL Multiphysics as a simulator, a numerical simulation was conducted based on experimental data. The study examined the impact of cooling temperature on hydride temperature evolution. Results revealed that hydrogen desorption kinetics of the amorphous Mg50Ni50 alloy are more significant compared to those of Mg2Ni compounds. Moreover, the effect of the warming temperature on the equilibrium pressure can also be observed in the hydrogen desorption isotherm curves. The experimental study of the Mg50Ni50 alloy provided activation energy data, along with determination of hydride formation enthalpy and entropy. On the other hand, we showed that the hydride temperature is maximum at the hydride-hydrogen interface within the hydride center.

Effect of double substitution on hydrogen absorption-desorption properties of Ti2CrV alloy

Doubly substituted Ti2CrV alloy with composition Ti1.5Sc0.3CrVNi0.2 was prepared by arc melting method followed by annealing. The annealed alloy exists in body centred cubic (BCC) structure and shows fast kinetics for hydrogen absorption and desorption at room temperature. BCC phase of the alloy undergoes phase transformation to face centred cubic (FCC) hydride phase with H atoms occupying tetrahedral sites in the lattice, reaching an overall H/M ratio >2.2 (storage capacity ∼ 4 wt%). Storage capacity decreases by 40% in the 2nd cycle and then stabilizes at a value of ∼2.5 wt% for the subsequent 10 cycles. A drastic reduction in hydride desorption temperature upon double substitution (Sc and Ni substitution in Ti2CrV alloy) has been confirmed by DSC studies. Furthermore, the change in isotope effect in doubly substituted Ti2CrV alloy is discussed in light of thermal stabilities of the hydrides and deuterides.

Water adsorption on microporous chabazites as thermal energy storage materials

Thermochemical energy storage can reduce fossil fuel consumption, which is still dominant in heating of buildings. The efficiency of the sorption technology is determined by the performance of the adsorbent, which should have a high water adsorption capacity and, consequently, a high energy storage density, stability under humid conditions, and fast kinetics of adsorption and desorption. In this study we investigated the effect of different elemental compositions of the commercial and laboratory prepared microporous aluminophosphates, natural and synthetic zeolites with chabazite structure and their modifications in powder and granular form on water adsorption capacity. The highest water uptake among the aluminophosphates was found for APO-34-IL, which was prepared by green synthesis with the low cost ionic liquid, while the highest water uptake of all the samples analysed was found for the composites of the natural zeolite with CaCl2.

Phosphorus sorption–desorption changes phosphorus fraction dynamic in a desert revegetation chronosequence

AbstractUnderstanding the characteristics of soil phosphorus (P) sorption and desorption is essential for comprehending P biogeochemical cycling and effectively managing ecosystems in a desert revegetation chronosequence. The present study utilized the Freundlich model and enzymatic activity to characterize the features of P sorption–desorption, and microbial activity, which aims to elucidate the effect of P kinetics and microbial activity on P fractions in the soils of a desert revegetation chronosequence, consisting of 11, 31, 40, 57, and 65 years old revegetated deserts. The findings revealed that the 31 years old soil showed the highest alkaline phosphomonoesterase and phosphodiesterase activities, and the 40 years old displayed the highest inorganic pyrophosphatase activity. In revegetated desert soils, microbial activity changed P sorption–desorption kinetics by decreased or increased the parameters including sorption/desorption energy site, P sorption/desorption ability, and the maximum buffering capacity of P sorption/desorption. And in microbial activity soils of 31–40 years old, P desorption significantly decreased T‐P and A‐P concentrations (p &lt; 0.05). P sorption process and enzyme activity explained 35.10% and 22.20% of P fraction variation, respectively; and P desorption process and enzyme activity explained 48.3% and 22.3% of P fraction variation, respectively. These findings provide valuable insights into the contribution of P kinetics coupled with microbial activity in desert ecosystems, aiding in the effective management of these fragile ecosystems.

Robust Chemiresistive Behavior in Conductive Polymer/MOF Composites.

Metal-organic frameworks (MOFs) are promising materials for gas sensing but are often limited to single-use detection. A hybridization strategy is demonstrated synergistically deploying conductive MOFs (cMOFs) and conductive polymers (cPs) as two complementary mixed ionic-electronic conductors in high-performing stand-alone chemiresistors. This work presents significant improvement in i) sensor recovery kinetics, ii) cycling stability, and iii) dynamic range at room temperature. The effect of hybridization across well-studied cMOFs is demonstrated based on 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 2,3,6,7,10,11-hexaiminotriphenylene (HITP) ligands with varied metal nodes (Co, Cu, Ni). A comprehensive mechanistic study is conducted to relate energy band alignments at the heterojunctions between the MOFs and the polymer with sensing thermodynamics and binding kinetics. The findings reveal that hole enrichment of the cMOF component upon hybridization leads to selective enhancement in desorption kinetics, enabling significantly improved sensor recovery at room temperature, and thus long-term response retention. This mechanism is further supported by density functional theory calculations on sorbate-analyte interactions. It is also found that alloying cPs and cMOFs enables facile thin film co-processing and device integration, potentially unlocking the use of these hybrid conductors in diverse electronic applications.

Amorphous mixed transition metal oxides: A novel catalyst for boosting dehydrogenation of MgH2

Magnesium hydride (MgH2) has been recognized as a promising hydrogen storage material. However, the sluggish hydrogen desorption kinetics is one of the main factors hindering its practical applications. To enhance the dehydrogenation kinetics of MgH2, an amorphous mixed TiO2-ZrO2-V2O5 catalyst is synthesized in this work. After adding the as-synthesized catalyst into MgH2 by ball milling, the dehydrogenation activation energy can be decreased to 65.7 kJ mol−1. Meanwhile, the catalyzed MgH2 shows excellent cycling stability after fifty hydrogen absorption-desorption cycles. The significant improvement of hydrogen desorption kinetics is attributed to the synergistic effect of abundant oxygen vacancies and in situ formed multivalent species in the catalyst. This highlights the importance of designing and synthesizing efficient catalysts for dehydrogenation of MgH2.

Effect of Reinforcement Ratio and Particle Size on the Physical and Mechanical Performance of Epoxy Matrix Panels and Waste Wood from Iroko Chlorophora excelsa from Cameroon

The use of local materials developed from natural reinforcements remains a major challenge for many researchers in the development of the industry and the fight against pollution. The wood industry generates large quantities of environmental waste, including Iroko wood. To give Iroko a second life, this study uses Iroko sawdust waste to make an epoxy matrix composite material. The composite was produced using a cold pressing technique based on moving the top and bottom plates to a thickness of 10 mm. On this basis, three particle sizes [t &lt; 0.35[, [0.35–0.63[, and [0.63–1[ were used, as well as three reinforcement (R)/matrix (M) percentages of 50R/50M, 60R/40M, and 70R/30M, where R is the reinforcement percentage and M is the matrix percentage. The physical tests, apparent and real density, porosity, moisture content, water absorption rate, absorption and desorption kinetics, diffusion theory, and activation energy were determined by the gravimetric method. A three-point bending test was carried out in accordance with the ASTM D790 for mechanical tests. The results show that the addition of Iroko particles lightens the material by reducing its density. The hydrophilic nature of Iroko particles increases the absorption rate and porosity, with good diffusion capacity as the particle size and percentage increase. The material produced can be light and porous, with possible applications in thermal insulation. In terms of kinetics, Verma et al.’s model best correlates the experimental desorption points for the 3 isotherms, while Page’s model best correlates the water absorption points. The mechanical results show that Young’s modulus and stress at break decrease with an increase in the reinforcement percentage and particle size. The mechanical results can be used to define the material’s applications in construction and furniture. In accordance with the EN312 standard, the composites produced can be classified as type 2 lightweight materials, suitable for use in dry and damp areas.

Understanding platinum-based H2 adsorption/ desorption kinetics during catalytic hydrogenation or hydrogen storage-related reactions

Hydrogen is among the most promising energy carriers and plays an important role on the way to sustainable technologies. Platinum holds great promise for unlocking the potential of renewable hydrogen, as it is an essential component of proton exchange membrane technologies and in various hydrogenation reactions. For the variety of applications of energy harvesting, conversion, and storage, the optimization and reduction of Pt loading is crucial. In view of this, a platinum catalyst using a stable SiO2 support is synthesized to investigate the adsorption/desorption behavior of hydrogen on platinum nanoparticles of different sizes, obtained by treating the sample at different calcination temperatures. Pulsed chemisorption and subsequent temperature-programmed desorption are described mathematically to obtain kinetic parameters. It is shown that higher adsorption capacities could be obtained using smaller particles. However, for particles smaller than 2.4 nm, higher Pt2+ content decreases H2 adsorption. Adsorption inhibition due to the presence of monatomic Pt cannot be excluded. The size of the Pt nanoparticles does not significantly affect the desorption/adsorption energy, but there is evidence that the hydrogen adsorbed per Pt atom at the surface varies with size: about 1 for single crystal planes and 2 for nanoparticles <3 nm.

Comprehensive laboratory constraints on thermal desorption of interstellar ice analogues

Gas accretion and sublimation in various astrophysical conditions are crucial aspects of our understanding of the chemical evolution of the interstellar medium. To explain grain growth and destruction in warm media, ice mantle formation and sublimation in cold media, and gas line emission spectroscopy, astrochemical models must mimic the gas--solid abundance ratio. Ice-sublimation mechanisms determine the position of snow lines and the nature of gas emitted by and locked inside planetary bodies in star-forming regions. To interpret observations from the interplanetary and extragalactic interstellar mediums, gas phase abundances must be modelled correctly. We provide a collection of thermal desorption data for interstellar ice analogues, aiming to put constraints on the trapping efficiency of water ice, as well as data that can be used to evaluate astrochemical models. We conduct experiments on compact, amorphous H$_2$O films, involving pure ices as well as binary and ternary mixtures. By manipulating parameters in a controlled way, we generate a set of benchmarks to evaluate both the kinetics and thermodynamics in astrochemical models. We conducted temperature-programmed desorption experiments with increasing order of complexity of ice analogues of various chemical compositions and surface coverages using molecular beams in ultrahigh vacuum conditions (1 times 10$^ $ hPa) and low temperatures (10 K). We provide TPD curves of pure ices made of Ar, CO, CO$_2$, NH$_3$, CH$_3$OH, H$_2$O, and NH$_4^+$HCOO$^-$, their binary ice mixtures with compact amorphous H$_2$O, ternary mixtures of H$_2$O : CH$_3$OH : CO, and a water ice made in situ to investigate its trapping mechanisms. Each experiment includes the experimental parameters, ice desorption kinetics for pure species, and the desorption yield (gas--solid ratio) for ice mixtures. From the desorption yields, we find common trends in the trapping of molecules when their abundance is compared to water: compact amorphous water ices are capable of trapping up to 20&lt;!PCT!&gt; of volatiles (Ar, CO, and CO$_2$), sim 3&lt;!PCT!&gt; of CH$_3$OH, and sim 5&lt;!PCT!&gt; NH$_3$ in relation to the water content within the ice matrix; ammonium formate is not trapped in the water ice films, and compact amorphous water ice formed in situ has similar trapping capabilities to a compact amorphous water ice deposited using molecular beams. Deposited or formed in a very compact structure, amorphous water ice of less than 100 layers cannot trap a large fraction of other gases, including CO and CO$_2$. These desorption yields offer insights into the availability of species that can react and form interstellar complex organic molecules during the warm-up phase of ice mantles. Furthermore, in order to be reliable, gas-grain astrochemical models should be able to reproduce the desorption kinetics and desorption yield presented in our benchmark laboratory experiments.

Direct visualization of pyrene diffusion in polyethylene and polyoxymethylene passive samplers

While passive sampling of ultra-low aqueous concentrations of hydrophobic organic compounds in environmental aqueous media has emerged as a promising analytical technique, there is a lack of good understanding of the fundamental diffusive processes. In this research, we used a fluorophore, pyrene, as a model compound to track diffusion in polymers through absorption and environmental media exchange processes. We directly tracked the penetration of pyrene into polyethylene (PE) and polyoxymethylene (POM) rods during absorption from water by sectioning the rod after different stages of absorption and observing the fluorescence signal through a microscope. Diffusion profiles of pyrene in polymers were simulated by numerical integration of Fickian diffusion. The results indicated that the uptake process in PE is governed by Fick's law and the absorption and desorption kinetics are similar in this polymer. However, the observed uptake profiles of pyrene in POM were non-Fickian and the release kinetics out of POM was slower compared to uptake into the polymer. We show that slower desorption from POM makes corrections for nonequilibrium using performance reference compounds (PRCs) problematic for deployments in water or sediment where there is significant advection. However, for static sediment deployments, the overall kinetics of exchange is controlled by slow transport through sediment and the hysteretic behavior of POM may not preclude the use of PRCs to interpret equilibrium status.

Synthesis of struvite-enriched slow-release fertilizer using magnesium-modified biochar: Desorption and leaching mechanisms

To improve the retention and slow-release abilities of nitrogen (N) and phosphorus (P), an 82 %-purity struvite fertilizer (MAP-BC) was synthesized using magnesium-modified biochar and a solution with a 2:1 concentration ratio of NH4+ to PO43− at a pH of 8. Batch microscopic characterizations and soil column leaching experiments were conducted to study the retention and slow-release mechanisms and desorption kinetics of MAP-BC. The slow-release mechanism revealed that the dissolution rate of high-purity struvite was the dominant factor of NP slow release. The re-adsorption of NH4+ and PO43− by biochar and unconsumed MgO prolonged slow release. Mg2+ ionized by MgO could react with PO43− released from struvite to form Mg3(PO4)2. The internal biochar exhibited electrostatic attraction and pore restriction towards NH4+, while magnesium modification and nutrient loading formed a physical antioxidant barrier that ensured long-term release. The water diffusion experiment showed a higher cumulative release rate for PO43− compared to NH4+, whereas in soil column leaching, the trend was reversed, suggesting that soil's competitive adsorption facilitated the desorption of NH4+ from MAP-BC. During soil leaching, cumulative release rates of NH4+ and PO43− from chemical fertilizers were 3.55–3.62 times faster than those from MAP-BC. The dynamic test data for NH4+ and PO43− in MAP-BC fitted the Ritger-Peppas model best, predicting release periods of 163 days and 166 days, respectively. The leaching performances showed that MAP-BC reduced leaching solution volume by 5.58 % and significantly increased soil large aggregates content larger than 0.25 mm by 24.25 %. The soil nutrients retention and pH regulation by MAP-BC reduced leaching concentrations of NP. Furthermore, MAP-BC significantly enhanced plant growth, and it is more suitable as a NP source for long-term crops. Therefore, MAP-BC is expected to function as a long-term and slow-release fertilizer with the potential to minimize NP nutrient loss and replace part of quick-acting fertilizer.

Research of fiberglass and basalt textile laminates on the kinetics of sorption and desorption of moisture after exposure to cold climate conditions

A two-stage kinetics of moisture sorption is obtained at a temperature of 23 °C and a humidity of 68 % in fiberglass laminates and basalt textile laminates exposed in a cold climate (Yakutsk) for 2 and 4 years. The adequacy of the relaxation model of anomalous moisture diffusion at the first stage of sorption is shown and an assessment of the increase in moisture content at the second stage is given. Keywords:textile laminate, moisture sorption kinetics, anomalous diffusion, approximation, structure and properties of the composite, climatic aging kychkinplasma@mail.ru

Modeling the dehydration kinetic of grape pomace

Three mathematical models have been used to predict the dehydration kinetics of grape pomace. To the aim, three different temperatures have been set to determine the different desorption kinetics. All the dehydration kinetic data have been fitted to verify the predictive ability of the proposed models. The fitting goodness were assessed by using four coefficients: E‾%, RMSE, χ2, and R2. Results show that all the proposed models can adequately fit the experimental data. In particular, the Dual-Stage Type B model is the best one, whereas the Fick model is the worst. The soundness of the mathematical approach adopted was tested by assessing the dependence of the model's parameters on the testing temperature: only some parameters followed the expected trend. The computational complexity referred to each model was considered evaluating the suitability of the proposed models to describe the desorption kinetics. To sum up, the Dual-Stage Type B model is the most complex, whereas the simplest one is the Dual-Stage Type A model. Considering both suitability and complexity, the Dual-Stage Type A is the best model to predict the dehydration kinetic of grape pomace.

Enhancing solar-driven atmospheric water harvesting by a bilayer macroporous hydrogel

The adsorption-based atmospheric water harvesting technique has shown great potential in providing clean water. An ideal device for atmospheric water harvesting should enable the massive and quick release of water after it is rapidly absorbed by the moisture adsorbent. At present, however, the moisture adsorbent still experiences issues such as a slow water absorption rate, hampered adsorption–desorption kinetics, and a low total water yield. In this paper, a bilayer moisture adsorbent (BMA), which glues a hydrophilic macroporous layer for rapid water adsorption and a carbonized sunlight-absorbing layer for both water harvesting and desorption acceleration, is introduced. Further evidence suggests that it is the stable, fluffy, and rough porous structure of the BMA that helps to harvest atmospheric water efficiently. The fully carbonized BMA exhibits a water absorption capacity of up to 396% at a relative humidity of 90%, which is 20% higher than a monolayer sample. More importantly, the desorption efficiency of the half-carbonized BMA reaches 98% under 1 sun illumination. These results jointly demonstrate that the BMA can play the dual role of absorbing moisture and light, allowing for rapid atmospheric water harvesting, massive water storage, and efficient desorption under the light.

Accurate prediction bioaccessibility of PAHs in soil-earthworm system by novel magnetic solid phase extraction technique

Conventional chemical extraction methods may lead to overestimate or underestimate bioaccessibility due to their inability to provide realistic kinetic information regarding PAHs in soils. In this study, we propose the use of magnetic solid phase extraction (MSPE) technique for assessing the bioaccessibility of PAHs in the soil-earthworm system. Firstly, a novel polydopamine-coated magnetic core-shell microspheres (Fe3O4–C16@PDA) was developed by a one-pot sol-gel and self-polymerization method. The PDA coatings not only enhance the hydrophilicity of material surfaces but also exhibit excellent biocompatibility. The maximum adsorption capacity of Fe3O4–C16@PDA for 16 PAHs was 52.72 mg g−1, indicating that the proposed material fulfills the assessment requirements for highly contaminated soil. To compare the measurement of PAHs and their uptake by earthworms (Eisenia fetida), experiments were conducted using four different soils with varying properties. The desorption kinetics data obtained from these experiments demonstrated that the capability of the MSPE in accurately predicting the bioavailable portions of PAHs. After a 28-day exposure, the best predictor of bioavailable PAHs in earthworms was MSPE method exhibited the highest correlation coefficient (R2 > 0.90), and its slopes in the four soils were 0.972, 0.961, 1.012, and 0.962, respectively, all close to 1. These results demonstrate that the MSPE method successfully mimics the conditions encountered in soil-earthworm systems and effectively assess bioaccessibility of PAHs in soils.

Desorption lifetimes and activation energies influencing gas–surface interactions and multiphase chemical kinetics

Abstract. Adsorption and desorption of gases on liquid or solid substrates are involved in multiphase processes and heterogeneous chemical reactions. The desorption energy (Edes0), which depends on the intermolecular forces between adsorbate and substrate, determines the residence time of chemical species at interfaces. We show how Edes0 and temperature influence the net uptake or release of gas species, the rates of surface–bulk exchange and surface or bulk reactions, and the equilibration timescales of gas–particle partitioning. Using literature data, we derive a parameterization to estimate Edes0 for a wide range of chemical species based on the molecular mass, polarizability, and oxygen-to-carbon ratio of the desorbing species independent of substrate-specific properties, which is possible because of the dominant role of the desorbing species' properties. Correlations between Edes0 and the enthalpies of vaporization and solvation are rooted in molecular interactions. The relation between Edes0 and desorption kinetics reflects the key role of interfacial exchange in multiphase processes. For small molecules and semi-volatile organics (VOC, IVOC, SVOC), Edes0 values around 10–100 kJ mol−1 correspond to desorption lifetimes around nanoseconds to days at room temperature. Even higher values up to years are obtained at low temperatures and for low volatile organic compounds (LVOC, ELVOC/ULVOC) relevant for secondary organic aerosols (SOA). Implications are discussed for SOA formation, gas–particle partitioning, organic phase changes, and indoor surface chemistry. We expect these insights to advance the mechanistic and kinetic understanding of multiphase processes in atmospheric and environmental physical chemistry, aerosol science, materials science, and chemical engineering.

Probing the differences in CO2 adsorption/desorption behaviors of solid amine sorbents in fixed and fluidized beds

Circulating fluidized bed temperature swing adsorption (CFB-TSA) CO2 capture process using solid amine sorbents has become a widely recognized solution to reduce stationary sources CO2 emissions. The successful design and operation of the adsorber and desorber requires much information on the CO2 adsorption and desorption behaviors of the sorbents in fluidized bed reactors. However, among the existing studies, little attention has been paid to desorption performance, which is equally important as adsorption performance. And almost all of them were conducted in TGAs or fixed beds, the lack of research in fluidized beds making it difficult to guide the design of industrial fluidized bed reactors. In addition, the systematic comparison of the above-mentioned adsorption/desorption behaviors and bed hydrodynamics (e.g. pressure drops) in fixed and fluidized beds can help provide theoretical support for the optimization of adsorbers, desorbers and coolers, which has not been reported yet. Therefore, we for the first time investigated the CO2 adsorption/desorption behaviors as well as hydrodynamics in both fluidized and fixed beds using a solid amine sorbent in a temperature swing adsorption (TSA) experimental rig. The results show that the sorbent exhibits faster adsorption and desorption kinetics in fluidized beds than those in fixed beds, as reflected by the fitted parameters of the Avrami kinetic model and the change of bed temperature during adsorption and desorption tests. And the bed pressure drops in fluidized beds are also much lower than that in fixed beds, especially at high superficial gas velocities and high sorbent loadings. By further discussion, a fluidized bed can also achieve lower equipment investment and less sorbent loading compared to multiple fixed beds in parallel. This study demonstrates the advantages of fluidized beds over fixed beds in large-scale TSA units in view of higher reactor efficiency, lower energy consumption and equipment investment.