Sorption Rate Research Articles

Toxic dye removal by thermally modified lignocellulosic waste in a threephase air-lift reactor: Kinetic insights

This paper investigates the influence of the air flow rate in a three-phase air-lift reactor on the sorption of toxic dye, Brilliant green, onto a promising and efficient sorbent, sour cherry stone biochar. In order to gain a comprehensive insight into the sorbent/sorption behaviour, sour cherry stone biochar was characterized by Fourier transform infrared spectroscopy with attenuated total reflection, pH of the suspension, point of zero charge, scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction. The experiments were performed in an air-lift reactor using airflows of 2.50 and 5.55 dm3 h-1. The experimental data of sorption kinetics experiments were fitted by non-linear form of pseudo-first and, pseudo-second models as well as the Weber-Morris model based on intraparticle diffusion. The overall sorption rate was found to be limited by the Brilliant Green mass transport rate to the sorbent at a lower airflow and thus mixing intensity, while it was kinetically controlled at a higher rate following the pseudo-second order kinetic model. Furthermore, sorption at lower air flow was delayed by mass transfer resistance through the liquid boundary layer surrounding sorbent particles. Presented results clearly indicate that airflow intensity plays a significant role in the overall sorption kinetics and support possible application of the applied biochar for efficient Brilliant Green sorption.

Physicochemical properties of flowable composites using isobornyl methacrylate as diluent monomer.

this study sought to evaluate the effect of isobornyl methacrylate (IBOMA) as a diluent monomer on the physicochemical properties of experimental flowable resin composites. the organic resin matrix of a modal flowable resin composite was formulated with 50 wt.% of bisphenol-A-glycidyl methacrylate (Bis-GMA) and 50 wt.% of a diluent monomer, in which IBOMA was used as a combining or substituent diluent monomer to triethylene glycol dimethacrylate (TEGDMA). The resin matrices were filled with 55 wt.% particles, of which 10 wt.% was 0.05-μm fumed silica, and 45 wt.% was 0.7-μm BaBSiO2 glass. Polymerization shrinkage stress (PSS; n=10), degree of conversion (DC; n=3), maximum rate of polymerization (Rpmax; n=3), film thickness (FT; n=10), sorption (Wsp; n=10), solubility (Wsl; n=10), flexural strength (FS; n=10), flexural modulus (FM; n=10), Knoop microhardness (KH; n=10), and microhardness reduction after chemical softening (HR; n=10) were evaluated. Data were analyzed using one-way ANOVA, followed by Tukey's test (α=0.05; β=0.2). the results showed that the substitution or addition of IBOMA reduced FT (p=0.001), PSS (p=0.013), Rpmax (p=0.001), DC (p=0.001), FM (p=0.006) Wsp (p=0.032), and Wsl (p=0.021). However, when used as a complete substituent, IBOMA demonstrated significantly lower FS (p=0.017) and KH (p=0.008), while TEGDMA demonstrated significantly lower HR (p=0.022). the flowable composite containing IBOMA combined with TEGDMA showed no effect in KH and FS and effectively reduced the PSS, RP, FT, Wsp, and Wsl. However, it showed a reduction in DC, FS, and an increase in HR.

Structural and sorption characteristics of an aerogel composite material loaded with flufenamic acid: insights from MAS NMR and high-pressure NOESY studies.

The structural and sorption characteristics of a composite material consisting of a silica aerogel loaded with flufenamic acid were investigated using a variety of nuclear magnetic resonance techniques. The composite structure was analyzed using magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, which revealed significant interactions between the aerogel matrix and the FFA molecules. Solid-state 29Si NMR provided insights into the aerogel's stability, while 1H and 13C NMR confirmed the presence of FFA in the matrix, with signals from FFA molecules observed alongside tetraethoxysilane (TEOS) groups. Ethanol-induced desorption of FFA led to narrowed spectral lines, suggesting the breaking of intermolecular hydrogen bonds. 19F MAS NMR spectra indicated changes in FFA local environments upon loading into AG pores. Evaluation of CO2 sorption characteristics using 13C NMR demonstrated a slower sorption rate for AG + FFA than that for pure AG, attributed to decreased pore volume. Furthermore, nuclear Overhauser effect spectroscopy (NOESY) was employed to explore the conformational behavior of FFA within the aerogel matrix. The results indicated a shift in conformer populations, particularly those related to the rotation of one cyclic fragment relative to the other. These findings provide insights into the structural and sorption characteristics of the AG + FFA composite, which are valuable for developing novel drug solid forms.

ГИДРОФОБНЫХ ПОВЕРХНОСТНЫХ СОЕДИНЕНИЙ МЕТАЛЛОВ ТВЕРДОТЕЛЬНЫМ СИНТЕЗОМ С ПРИМЕНЕНИЕМ КРЕМНИЙГИДРИДНЫХ РЕАГЕНТОВ

A study of the formation of hydrophobic properties of dispersed metal samples (Ni, Fe, Cu, Al) obtained by different methods was carried out. The methods used are based on chemical processes, including chemisorption and reduction, during the interaction of a solid with gaseous modifier substances. The time dependence in the interval 24-216 (h) of the sorption of water (a) from saturated vapor on samples of copper powder (PMS-1) coated with ammonium preparations (Triamon and Alkamon) was studied. For the first time, the dependence of the sorption rate da/dt for the named samples was obtained and approximated by an equation based on the Gaussian function. Using XPS spectroscopy, structural changes in the surface of modified dispersed aluminum (PAP-2) were revealed upon interaction with water vapor. The binding energies of the O1s oxygen peaks (531.2; 531.5 eV), reflecting this interaction, were determined and assigned. There is no noticeable oxidation of aluminum on the surface. It was revealed that after 10 days of interaction with saturated water vapor, the proportion of aluminum atoms on the surface of the powder modified with vapors of organosilicon liquid based on ethyl hydride siloxane increases. It is assumed that the observed effect is due to the “pushing out” of water molecules from the hydrophobized surface during prolonged treatment, which is confirmed by the graph of the experimental dependence a=f(t). The higher hydrophobicity of metal products of solid- state hydride synthesis compared to industrial nickel and copper powders modified from the gas phase with known water-repellent agents based on ammonium and organosilicon compounds was experimentally confirmed. An explanation was proposed for the decrease in nonlinear effects in the time dependences of a(t) for dispersed metals – products of solid-state hydride synthesis.

Sorption Kinetics and Equilibrium Isotherms of Phosphine Gas into Wheat Kernels

Highlights The pseudo-first order kinetic model fits well with the experimental data of sorbed phosphine versus time. Sorption isotherm curves were developed using Langmuir, Freundlich, and Redlich-Peterson models. Phosphine adsorption capacity of wheat kernels increased with increase in applied concentration (400-2400 ppm). Abstract. Phosphine (PH3) is the most used fumigant in the U.S. due to its low price, ease of use, and wide accessibility. With the growing concerns of phosphine-resistant insect pests, the sustainability of PH3 as an effective fumigant has been put at risk. Sorption equilibrium data is critical for improving the accuracy of modeling studies for phosphine-wheat fumigation systems and would clarify the PH3 uptake and sorption capacity of wheat. The objectives of this study were to determine the effect of initial concentration (from 400 to 2400 ppm) on the equilibrium concentration for PH3 in wheat kernels and on cumulative and daily PH3 sorption through time. Kinetic data showed the sorption process was time-dependent and occurred in two phases: an initial faster adsorption phase, followed by a phase with a slower sorption rate as the grain and PH3 reached equilibrium. Pseudo-first and pseudo-second order models were fit to PH3 concentrations versus time experimental data. The pseudo-first order model provided better equilibrium estimates and was used for the sorption isotherm analysis. Langmuir, Freundlich, and Redlich-Peterson sorption isotherm models were fit to the plot of equilibrium headspace gas concentration versus sorbed PH3 quantity. All three models had low standard errors of prediction (0.46-0.47). These PH3 sorption kinetics and values of total sorbed quantity at equilibrium are valuable for modeling the rate and maximum quantity of PH3 uptake in wheat. Keywords: Fumigation, Kinetics, Phosphine, Sorption Isotherm, Wheat.

Semi-analytical models for two-dimensional multispecies transport of sequentially degradation products influenced by rate-limited sorption subject to arbitrary time-dependent inlet boundary conditions

Most of the semi-analytical and analytical models employed to depict multidimensional, multispecies transport of sequentially degrading reaction products are built upon solving a set of coupled advection-dispersion equations (ADEs). Within these equations, sorption is considered as being equilibrium-controlled. However, it has been demonstrated that more realistic predictions of the transport of contaminants in the groundwater could be obtained by the use of a rate-limited sorption process instead of an equilibrium sorption assumption. This study is thus designed to devise semi-analytical models for the two-dimensional multispecies transport of a chemical mixture comprised of a parent compound and its degradation-daughter products which is influenced by rate-limited sorption subject to arbitrary time-dependent inlet boundary conditions. Three integral transforms are applied to generate a set of linear algebraic equations (AEs) resulting from the reductions of the ADEs. The contaminant concentration of each species is calculated by solving these AEs and then retransforming the solutions back to the original time-space domain. The simulation results obtained with our newly developed semi-analytical model are nearly identical to those generated using a numerical model based on the Laplace transform finite difference (LTFD) method. This confirms the validity of the new semi-analytical model. An investigation of the effect of rate-limited sorption on the migration of the contaminant plume is carried out using various time-dependent inlet boundary conditions. The sorption rate values vary from low to high, specifically, 0.05, 0.5, 5, and 50 years−1. The results show that the predicted concentrations of all contaminants within in the decay chain decrease as the sorption rate constant increases, for both constant and exponentially time-dependent boundary sources. However, under pulse loading boundary conditions, the concentrations of the later degradation products tend to increase with the sorption rate constant. The semi-analytical models created in this study, allow for different inlet boundary conditions, so can be utilized to simulate the transport of sequentially degrading reaction products. This greater accuracy makes them useful for many applications.

Performance characterisation and design considerations for a domestic ammonia/salt resorption heat pump

Heat pumps will play a key role in the future provision of low carbon domestic heating and the re-use of industrial waste heat. Adsorption cycle heat pumps are advantageous in that they can use the existing natural gas network to avoid electricity supply limitations across the UK. A 2 kW domestic-scale ammonia/salt heat pump demonstrator is currently being tested at the University of Warwick as a replacement for a conventional condensing gas boiler. This paper describes analysis work in support of this testing which will lead to design refinements in follow-on developments.A Matlab-based 2D transient simulation package was developed to study heat transfer and reaction rate within a pair of linked reactors. Heat conduction and sorption rate are modelled together with inter-reactor gas flows and parasitic heat loss. Novel features include the use of Matlab's linked ODE solvers for convergence (ODE15S was found to be fastest) and the script file input configuration which combines clear visibility of parameters with the ability to run multiple simulations to show the effect of parametric variations. The code facilitates rapid design optimisation.Eleven cycle parameters have been investigated, including filling pressure, heat transfer coefficients, salt ratio, source temperatures, void space and heat capacity. The choice of cycle period involves a compromise between coefficient of performance and power output. A water/glycol heat transfer fluid gives better COP and output power than thermal oil. Insulation within the reactor shell has the potential to limit shell transient heat exchange but void space effects are likely to be more significant. The heat capacity of fluid in pipes and manifolds should be minimised.COP = 1.31 is achieved at 45 °C delivery; 60 °C for hot water is possible but with lower COP. The best results for space heating are obtained with source temperatures above -5 °C.

New insights into the adsorptive characteristics of trihalomethane precursors from surface water using magnetic powdered activated carbon

Powdered activated carbon (PAC) can effectively eliminate dissolved organic matter (DOM) as a precursor of trihalomethane (THM), but its application has raised concerns regarding its separation and the overelevated formation of brominate THM species in treated water after chlorination. Although magnetic PAC (Mag-PAC) has been proposed as an easily separable adsorbent for water treatment, its removal by Mag-PAC remains unknown. In this study, a novel Mag-PAC adsorbent for removing DOM and controlling THM formation from surface water was fabricated, evaluated using batch experiments, and compared with PAC. Our results found that Mag-PAC blended the advantages of PAC and magnetic particles, having an efficient removal performance toward DOM with an adsorption capacity of 2.84–3.69 mg-C/g and good magnetic separability of 10.15 emu/g. The iron oxide coating on the carbon matrices was predominantly distributed in the presence of crystalline goethite and magnetite structures. Chemisorption was the dominant mechanism of DOM adsorption by Mag-PAC. The sorption rate of DOM was influenced by the impregnation of iron oxide, but such impregnation did not significantly affect the DOM adsorption capacity. Aromatic DOM, humic-acid and fulvic-acid like compounds were efficiently adsorbed by the Mag-PAC. Compared with PAC, Mag-PAC exhibited a higher reduction in lifetime cancer risks from THMs through the ingestion pathway by decreasing the formation potential of trichloromethane and bromodichloromethane, which generated high unit risks among various THM species. These findings highlight the potential of Mag-PAC as an effective sorbent for DOM removal to control the formation of THM in surface water.

3D Printed Cellulose Nanofiber Aerogel Scaffold with Hierarchical Porous Structures for Fast Solar-Driven Atmospheric Water Harvesting.

Hygroscopic salt-based composite sorbents are considered ideal candidates for solar-driven atmospheric water harvesting. The primary challenge for the sorbents lies in exposing more hygroscopically active sites to the surrounding air while preventing salt leakage. Herein, a hierarchically structured scaffold is constructed by integrating cellulose nanofiber and lithium chloride (LiCl) as building blocks through 3D printing combined with freeze-drying. The milli/micrometer multiscale pores can effectively confine LiCl and simultaneously provide a more exposed active area for water sorption and release, accelerating both water sorption and evaporation kinetics of the 3D printed structure. Compared to a conventional freeze-dried aerogel, the 3D printed scaffold exhibits a water sorption rate that is increased 1.6-fold, along with a more than 2.4-fold greater water release rate. An array of bilayer scaffolds is demonstrated, which can produce 0.63g g-1 day-1 of water outdoors under natural sunlight. This article provides a sustainable strategy for collecting freshwater from the atmosphere.

Water Sorption in Hybrid Polyester/Glass/Jute Composites Processed via Compression Molding and Vacuum-Assisted Resin Transfer Molding.

The aim of this work is to analyze water sorption in hybrid polyester/glass fabric/jute fabric composites molded via compression and VARTM (Vacuum-Assisted Resin Transfer Molding). The laminates were produced with five different stacking sequences and subjected to water sorption testing at room temperature, 50 °C and 70 °C. This study consisted of two stages: experimental and theoretical stages. The composites had a fiber volume content ranging from 30% to 40%. Water absorption and diffusion coefficient in the hybrid composites were intermediate to those reinforced with a single type of fiber. There were no significant differences in these properties based on fiber arrangement once the composites reached saturation. Diffusion coefficient values were higher for specimens with jute fiber on at least one of the outer surfaces. Water sorption rates increased with higher immersion temperatures. The water sorption at saturation point was not affected by the manufacturing process. Among the hybrid composites, those with jute on the surfaces showed the highest diffusion coefficient, while those with glass on the surface had the lowest values. Higher diffusion coefficient values were observed at temperatures of 50 °C and 70 °C. The main influencing factors on the absorbed moisture content for composites are the presence and content of jute fibers in the system and the immersion temperature. The manufacturing process does not affect the water sorption at saturation point.

Evaluation of a pH- and time-dependent model for the sorption of heavy metal cations by poultry litter-derived biochar

Common isotherm and kinetic models cannot describe the pH-dependent sorption of heavy metal cations by biochar. In this paper, we evaluated a pH-dependent, equilibrium/kinetic model for describing the sorption of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) by poultry litter-derived biochar (PLB). We performed sorption experiments across a range of solution pH, initial metal concentration, and reaction time. The sorption of all five metals increased with increasing pH. For Cd, Cu, and Pb, kinetics experiments demonstrated that sorption rates were greater at pH 6.5 than at pH 4.5. For each metal, all sorption data were described using single set of four adjustable parameters. Sorption edge and isotherm data were well described with R2 > 0.93 in all cases. Time-dependent sorption was well described (R2 ≥ 0.90) for all metals except Pb (R2 = 0.77). We then used the best-fit model parameters to calculate linear distribution coefficients (KD) and equilibration times as a function of pH and initial solution concentration. These calculations provide a more robust way of characterizing biochar affinity for metal cations than Freundlich distribution coefficients or Langmuir sorption capacity. Because this model can characterize metal cation sorption by biochar across a wider range of reaction conditions than traditional isotherm or kinetic models, it is better suited for estimating metal cation/biochar interactions in engineered or natural systems.

Engineered MoSe2-rGO composite for efficient recovery of viscous crude oil spills

High-performance photothermal materials capable of harnessing the entire solar spectrum have garnered significant interest in developing solar-heating sorbents for the effective recovery of viscous oil. Herein, we developed narrow-bandgap MoSe2-loaded reduced graphene oxide (MoSe2-rGO) nanocomposite with efficient solar utilization. MoSe2-rGO with synergistically-enhanced light absorption and photothermal conversion, was first employed for fabricating melamine sponge (MS)-based sorbent (PMGP/MS sorbent) via a facile dip-coating method. The sorbent showed excellent solar-heating capability, reaching a surface temperature of 78 °C in 100 s under 1.0 sun. The sorbent proved effective in recovering highly viscous oil via solar-motivated viscosity-reduction of oil. The sorption rate for viscous crude oil increased 10.6 times under 1.0 sun compared with no sunlight illumination, and the sorption saturation reached around 55.6 g/g within 750 s. Moreover, continuous sorption was achieved under a self-priming pump based on the reduced viscosity and increased fluidity, with capacity of 1.1 g/cm2 at 650 s under 1.0 sun.

Improving Atmospheric Water Harvesting in Carbon‐Based Sorbents Through CO2 Activation

AbstractAtmospheric water harvesting (AWH) can serve as an alternative fresh water source in regions with scarce access to drinking water. While many techniques are geographically or seasonally limited, sorbent‐based AWH shows the potential for wider application. Low‐cost, carbon‐based sorbents named nanoporous sponges (NPS) are recently developed, exhibiting fast and repeatable water uptake of 0.14 g g−1 at 90% relative pressure. While useful from a cost and daily water yield point of view, there is room for improvement. This article presents an improved production process combining pyrolysis and activation under CO2 in a single step, yielding improved NPS capable of reproducibly reaching a water uptake of 0.47 g g−1 at 95% relative pressure while maintaining fast sorption rates. The NPS show significant endurance and are able to maintain stable performance over numerous humidity cycles. An unexpected time‐dependant sorption behavior is also identified for NPS produced with a modified synthesis formulation, due to an increase in sodium carbonate residual content.

Enhanced removal of short- and long-chain per- and poly-fluoroalkyl substances from aqueous phase using crushed grafted chitosan beads: Performance and mechanisms

The widespread use of per- and poly-fluoroalkyl substances (PFASs), environmentally persistent halogenated hydrocarbons, in various industrial and commercial applications has caused significant concerns owing to their contamination of soil and groundwater. Chitosan is a biopolymer substance with abundant amine and hydroxyl functional groups, making it a good candidate for adsorption of PFASs. This study aimed to increase chitosan's adsorption capacity by grafting additional amine functional groups on its surface for the removal of long- and short-chain PFASs from an aqueous phase. Two types of chitosan-based sorbents were developed: crushed chitosan beads (CBs) and polyethyleneimine-grafted CBs (GCBs). Batch adsorption tests assessed the adsorption capacities of the sorbents in terms of the sorption kinetics, isotherms, selectivity, and reusability. Based on the results, the GCBs had significant potential for adsorbing PFASs. These capacities were significantly higher than those demonstrated by the CBs. The sorption kinetics data revealed that the GCBs had a fast sorption rate. Furthermore, the GCBs demonstrated a high adsorption affinity, with log Kd values ranging from 1.5 to 2.5 for PFASs at environmentally relevant concentrations (1000 ng L−1). They also demonstrated excellent selectivity sorption for these compounds, even in the presence of other organic and inorganic pollutants.

The Interaction of Pesticides with Humin Fractions and Their Potential Impact on Non-Extractable Residue Formation.

The constant influx of pesticides into soils is a key environmental issue in terms of their potential retention in the soil, thus reducing their negative impact on the environment. Soil organic matter (SOM) is an important factor influencing the environmental fate of these substances. Therefore, the aim of this research was to assess the chemical behavior of pesticides (flufenacet, pendimethalin, α-cypermethrin, metazachlor, acetamiprid) toward stable soil humin fractions (HNs) as a main factor affecting the formation of non-extractable residues of agrochemicals in soil. This research was conducted as a batch experiment according to OECD Guideline 106. For this purpose, HNs were isolated from eight soils with different physicochemical properties (clay content = 16-47%, pHKCl = 5.6-7.7, TOC = 13.3-49.7 g·kg-1, TN = 1.06-2.90 g·kg-1, TOC/TN = 11.4-13.7) to reflect the various processes of their formation. The extraction was carried out through the sequential separation of humic acids with 0.1 M NaOH, and then the digestion of the remaining mineral fraction with 10% HF/HCl. The pesticide concentrations were detected using GC-MS/MS. The pesticides were characterized based on the different sorption rates to HNs, according to the overall trend: metazachlor (95% of absorbed compound) > acetamiprid (94% of absorbed compound) > cypermethrin (63% of partitioning compound) > flufenacet (39% of partitioning compound) > pendimethalin (28% of partitioning compound). Cypermethrin and metazachlor exhibited the highest saturation dynamic, while the other agrochemicals were much more slowly attracted by the HNs. The obtained sorption kinetic data were congruous to the pseudo-first-order and pseudo-second-order models related to the surface adsorption and interparticle diffusion isotherm. The conducted research showed that the processes of pesticide sorption, apart from physicochemical phenomena, are also affected by the properties of the pollutants themselves (polarity, KOC) and the soil properties (SOM content, clay content, and pHKCl).

Phosphorus Sorption by Purple Soils in Relation to Their Properties: Investigation, Characterization, and Explanation

Improved soil phosphorus (P) management can be achieved through an understanding of regional soil–P interactions and their relation to soil properties. To this end, soil samples from different use types (paddy soils, dry farmland soils, forest soils, and urban green land soils) were collected from 10 sites across the west to the east of Sichuan Basin, China. These samples were analyzed to determine their P sorption properties and physical and chemical compositions. P sorption was described using a modified Freundlich equation. The results demonstrated a gradient in P sorption within the basin, characterized by higher values in urban areas and a west-to-east decrease trend, along with the null-point values of soil sorption–desorption equilibrium. This variation was linked to the extensive use of P fertilizer, which altered soil particle surface conditions and significantly reduced both the quantity and rate of subsequent fertilizer sorption. Furthermore, P sorption was found to be correlated with the soil clay fraction, amorphous aluminum oxides, and soil organic matter contents. Urban expansion and accelerated erosion of productive agricultural land increase mean soil particle size and may decrease soil P holding and retention capacity. As preliminary deterioration in soil properties was found, conservative soil management is needed to address the potential threats of soil degradation in the central Sichuan Basin.

Experimental study of lightweight concrete prepared from super absorbent polymers (SAPs) and glass fibers (GF)

ABSTRACT This study investigates the effect of super absorbent polymers (SAPs) and glass fiber (GF) additions on the properties of lightweight concrete. The SAPs act as a pore-forming agent, with the addition of various GF contents (0.1–1.0% by weight of dry ingredients). The results indicate that the use of SAPs at 7% by weight of OPC produces a product with similar properties to conventional lightweight concretes which meet the ASTM C332–17 standard. The addition of GF to the mixture tends to reduce the dry density and compressive strength, but increases the porosity and flexural strength. The results indicate that the use of SAPs at 7% by weight of OPC produces a product with similar properties to conventional lightweight concretes which meet the ASTM C332–17 standard. The 28-day compressive strengths decreased from 7.04 ± 0.07 for control sample to 4.59 ± 0.11 MPa, while the flexural strengths increased from 3.89 ± 0.04 for control sample to 6.72 ± 0.06 MPa. High-porosity lightweight concrete prepared from SAPs and GF shows reduced thermal conductivity and an increased sorption rate. The initial rate of water absorption gradually increases from 2.48 × 10−1 mm/sec0.5 in the sample without GF up to 5.45 × 10−1 mm/sec0.5 in the sample containing 1.0 wt.% GF. Comparison with the literature indicates that the use of SAPs as pore-forming agents in conjunction with GF has the potential to produce fiber-reinforced lightweight concrete with improved properties.

SORPTION OF SCANDUIUM AND YTTRIUM COMPOUNDS BY ZIRCONIA-SILICA NANOSORBENT

Physical and chemical regularities of sorption extraction of scandium and yttrium compounds from (0.1–2.5)∙10-4 M aqueous solutions by zirconium-silica nanosorbent with specific surface area of 900-1000 m2/g, pore radius of 3.5-7, 6 nm and with a ZrO2 content of 29% have been established. It is shown that the studied sorbent efficiently (>99%) removes scandium and yttrium at pH 8 – 10 (Sc) and pH 9 – 10.5 (Y) and at sorbent consumption of 0.4 g/dm3. The time to reach sorption equilibrium is 240 min (Sc) and 210 min (Y). Modeling of scandium and yttrium sorption kinetics by Boyd’s external diffusion and internal diffusion models shows that sorption takes place in a mixed diffusion mode. The values of sorption rate constants (0.018 min-1 Sc, 0.033 min-1 Y), external mass transfer constants (4.74 ∙ 10-8 m/min Sc, 8.51 ∙ 10-8 m/min Y) and internal diffusion rate constants (0.0099 min-1 Sc, 0.0093 min-1 Y) have been calculated. It is established that the kinetics of sorption follows the pseudo-second-order model. It is shown that the sorption isotherms of both investigated metals are described by Freundlich, Frumkin-Fowler-Guggenheim and Dubinin-Radushkevich models. The constants of sorption isotherm models, characteristic energy of sorption (10.79 kJ/mol Sc, 9.58 kJ/mol Y), ΔG0 of sorption (-32.82 kJ/mol Sc, -30.77 kJ/mol Y) are calculated. The results of calculations indicate a significant affinity of scandium and yttrium compounds for this sorbent, spontaneous nature of the process and mixed nature of sorption with a predominance of chemisorption, a significant contribution of ion exchange to the sorption mechanism.

Enhanced Water Sorption Performance of Polyacrylamide & Glass Fiber Paper Composites: Investigation and Comparison of Application in Desiccant Wheels.

The water sorption and desorption properties of solid adsorbent materials are crucial in rotary dehumidification systems. Metal organic frameworks (MOFs) and hydrogels are mostly at the laboratory stage due to factors like the synthesis process and yield. In this study, we utilized an eco-friendly and large-scale synthesis method to prepare polyacrylamide (PAM) hydrogels (yielding approximately 500 mL from a single polymerization). Subsequently, PAM was then coated onto glass fiber paper (GFP), which serves as a commonly employed substrate in desiccant wheels. By incorporating the hygroscopic salt LiCl and optimizing the content of each component, the water sorption performance of the composite was notably improved. The water sorption and desorption performances, as well as cycling stability, were evaluated and compared with composites containing aluminum fumarate, LiCl, and GFP (AlFum-LiCl&GFP). The results revealed that PAM-LiCl&GFP outperformed AlFum-LiCl&GFP in terms of sorption capacity throughout various relative humidity (RH) levels. It achieved a water uptake of 1.06 g·g-1 at 25 °C and 30% RH, corresponding to a water sorption rate coefficient K of 15.32 × 10-4 s-1. Furthermore, the lower desorption temperature (60 °C) resulting in a desorption ratio of 82.6%, along with the excellent cycling stability and effective performance as a desiccant wheel module, provide evidence for the potential application of PAM-LiCl&GFP in desiccant wheels.

CALCULATION OF THE ELECTRODE REACTION RATE ON A GRAPHITE CATHODE OF ALUMINUM-ION BATTERY WITH 1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE

A method for determining the rate of sorption of chloraluminate complexes on graphite material as the main cathode reaction in aluminum-ion batteries with an ionic liquid as an electrolyte is proposed in terms of classic chemical kinetics approach. The method is applied to the description of the rate of a one-electron cathode reaction that is in the case the sorption/desorption of complexes on the electrode surface with no migration in the interlayer space of graphite taken into account. The experimental part is based on the selection and providing of measurement conditions and the ratio of the components of the cell to ensure that the rate of the cathode process sets the rate of current generation of the cell. The rate of supply/removal of electrons, as participants in the reaction, thus can be directly related to the reaction rate on graphite. The point of reaching the limiting current on the polarization curve in that case corresponds the limiting rate of the chemical sorption reaction. The approach takes into account the effect of other limiting processes, such as the rate of removal/supply of electrons, the rate of removal/supply of ions to/from the electrolyte volume, and the rate of anodic dissolution/deposition of aluminum. The calculated value of the reaction rate for graphite material grade EC-02 and low-temperature ionic liquid 1-ethyl-3-methylimidazole chloride in a mixture with aluminum chloride (1 : 1.3) was calculated to be 46 µmol/cm2 · s.