Sorption Isotherms Research Articles

Photocatalytic mediated destruction of 2-chlorobiphenyl by a ZnO-[10%]BiOI p-n heterojunction: effect of some process parameters

This study involved the synthesis, characterization, and application of various photocatalysts and heterojunctions using zinc oxide (ZnO), tungsten trioxide (WO3), and bismuth oxyiodide (BiOI) for the photo-abatement of 2-chlorobiphenyl (2CBP). Scanning electron microscopy revealed a variety of morphologies for all composites, while energy-dispersive X-ray spectroscopy only identified reference elements and X-ray diffraction patterns displayed crystalline patterns with no impurity peaks. The absorbance of the heterostructures exhibited slight red shifts as WO3 and BiOI were etched into ZnO. Except for ZnO-[10%]WO3, the band gaps of all composites decreased/narrowed as the doping of WO3 and BiOI into ZnO increased. Nitrogen sorption isotherms revealed that almost all the prepared materials had a Type IV isotherm, and the heterostructures showed higher surface area measurements compared to the undoped composites. The ZnO-[10%]BiOI heterojunction, which displayed the best photoactivity, was further investigated to analyze the influence of some operating conditions. Results revealed that the initial pollutant concentration influenced the degree of photodegradation, which decreased with increased initial 2CBP concentration. The optimum photocatalytic performance was detected at neutral pH. The pseudo-first order kinetic model showed that doubling the heterojunction’s weight increased the rate constant from 0.0054 to 0.0089 min−1, while increasing the pH to 11.3 resulted in an 18-fold reduction. Overall, the study demonstrated the potential application of ZnO-[10%]BiOI heterostructure as a highly effective photocatalyst for recalcitrant contaminants in water.

Influence of temperature on non-exchange sorption of aromatic amino acids by anion exchanger AV-17-8

The equilibrium in thearomatic amino acid (tryptophan, phenylalanine, tyrosine and histidine) – anion exchanger AV-17-8 (Cl-) systems at different temperatures was investigated In order to identify the influence of both increased and decreased temperatures on the sorption equilibrium the temperature range was 277-343 K was studied. Sorption isotherms were obtained at 277, 293, and 343 K. The thermodynamic description of sorption systems was carried out using an approach based on the idea that the sorption process is stoichiometric. The integral and differential energy characteristics and the compensation effect between the enthalpy and entropy components for the studied sorption systems were calculated. A change in temperature led to a change in the physicochemical properties of the studied sorbates and sorbent. In the temperature range 277-243 K, the solvent content in the sorbent phase remained unchanged. A low solvent content at a temperature of 333 K and an increase in its amount at 343 K were experimentally established. It should be considered that at different temperatures the ionization constants of functional groups and the regions of existence of ionic forms of amino acids change, but the sorption mechanism does not change, since the recharging of amino acids did not occur. It was established that the process is exothermic for tryptophan and phenylalanine. With increasing temperature, the amount of sorbed substance decreased. The absorption energy was low due to the significant compensatory effect of enthalpy and entropy factors, the differential Gibbs energy was practically independent of temperature due to the stabilizing effect of hydrophobic forces in the sorbent phase. For the poorly soluble amino acid tyrosine, when the temperature increased from 277 to 293 K, a slight increase in sorption was observed, and with a further increase, a decrease to trace amounts was revealed. In the temperature range of 277-293 K, the sorption process was characterized by the formation of a supersaturated solution in the sorbent phase and was endothermic. The sorption of hydrophilic histidine increased with increasing temperature, which correlates with the solvent content in the sorbent phase, including low content at 333 K. The process of histidine sorption is endothermic, characterized by a strong dependence of the differential Gibbs energy on temperature and the absence of a compensation effect between the enthalpic and entropic components.

Equilibrium of sorption of Tribulus Terrestris steroid saponins on a natural polymer sorbent – chitosan

Steroidal saponins have a wide spectrum of pharmacological action and therefore are widely used in pharmacological practice. Chitosan is a unique material. Its biocompatibility, biodegradability, non-toxicity, as well as its cationic nature reveal the potential of this biopolymer as a carrier of drugs for their targeted delivery. The immobilization of biologically active substances can be carried out in a variety of ways - nanomicelles with an encapsulated drug or their polyelectrolyte complexes with oligochitosans, depending on the nature of the active substance. The study of the sorption of saponins by chitosan under equilibrium conditions was studied. An analysis of the equilibrium curves of sorption of Tribulus Terrestris saponin on chitosan was carried out. The presence of a local minimum on the isotherm in the region of solution concentrations corresponding to micellization was revealed. It has been established that the course of the saponin sorption isotherm is determined by competing association processes in a solution and on the surface of chitosan. The pH of the solution did not change, which indicated the absence of ionic interactions involving the protonated amino group of chitosan. The moisture content of chitosan during the sorption of saponin was studied. The antibatic nature of the absorption curves and moisture content curves of chitosan was revealed. An analysis of the saponin sorption isotherm was carried out using the adsorption theories of Langmuir, Freundlich, and BET. High values of the correlation coefficients allowed us to use the Freundlich equation for a quantitative description of the isotherm in the initial section, and to analyse the entire isotherm using the BET theory, which takes into account the polymolecular nature of sorption. The results obtained for the description of the sorption isotherm of saponin were consistent with the proposed mechanism of its absorption by chitosan. Using IR spectroscopy, it was established that the interaction in the sorbent-sorbate system was due to the emerging hydrogen bonds between the amino and hydroxyl groups of chitosan and the hydroxyl groups of saponin carbohydrates. The results obtained, as well as literature data, confirm the formation of cavities in polysaccharides into which saponin is “incorporated”. In our case, the presence of cavities formed by seven monomer fragments of chitosan, the stability of which is fixed by hydrogen bonds was discussed.

Effect of Wheat Residue-Derived Biochar on Naphthalene Adsorption in Loess Soil in Northwest China

Research on the environmental behavior of polycyclic aromatic hydrocarbons (PAHs) in soil is limited, particularly regarding the influence of biochar on naphthalene (NAP) adsorption on the loess soil of Northwest China. In this study, a batch equilibrium experiment was used to analyze the sorption kinetics, sorption isotherms, and influencing factors of NAP adsorption by biochar derived from wheat residue at various pyrolysis temperatures on loess soil. The results indicated that NAP adsorption onto biochar-modified soil was rapid, within 6 h, and reached equilibrium after 20 h. The sorption kinetics was accurately described by a pseudo-second-order model. Additionally, the sorption isotherms were best described by the Freundlich model, indicating a multilayer adsorption mechanism. The average value of KF decreased as follows: BC-600 (2.03) > BC-400 (1.52) > BC-200 (1.25) > soil (0.91), indicating that biochar addition was beneficial for the adsorption of NAP on loess soil. The Gibbs free energy (ΔGθ) of NAP was less than zero, and the enthalpy (ΔHθ) and entropy (ΔSθ) values were greater than zero, suggesting that the adsorption occurred spontaneously through an endothermic reaction. Furthermore, the initial concentration of NAP influenced its adsorption amount. Pyrolysis temperatures of 400 °C and 600 °C resulted in higher NAP adsorption capacities, highlighting the beneficial effect of biochar addition on enhancing NAP adsorption in loess soil. However, at a pyrolysis temperature of 200 °C, the process of carbonization became incomplete, resulting in a reduction in the adsorption amount.

Microplastic-Assisted Removal of Phosphorus and Ammonium Using Date Palm Waste Derived Biochar.

Microplastics (MPs) are emerging environmental pollutants worldwide, posing potential health risks. Moreover, MPs may act as vectors for other contaminants and affect their fate, transport, and deposition in the environment. Therefore, efficient and economical techniques are needed for the removal of contemporary MPs and contaminants from the environment. The present research study investigated the sorption of phosphorus (P) and ammonium (NH4+) onto date palm waste-derived biochar (BC) from an aqueous solution in the presence of polyamide (PA) and polyethylene (PE) MPs. The BC was prepared at 600 °C, characterized for physio-chemical properties, and applied for P and NH4+ removal via isotherm and kinetic sorption trials. The results of the sorption trials demonstrated the highest removal of NH4+ and P was obtained at neutral pH 7. The highest P sorption (93.23 mg g-1) by BC was recorded in the presence of PA, while the highest NH4+ sorption (103.76 mg g-1) was found with co-occurring PE in an aqueous solution. Sorption isotherm and kinetics models revealed that P and NH4+ removal by MP-amended BC followed chemisorption, electrostatic interaction, precipitation, diffusion, and ion exchange mechanisms. Overall, co-existing PA enhanced the removal of P and NH4+ by 66% and 7.7%, respectively, while co-existing PE increased the removal of P and NH4+ by 55% and 30%, respectively, through the tested BC. Our findings suggested that converting date palm waste into BC could be used as a competent and economical approach to removing P and NH4+ from contaminated water. Furthermore, microplastics such as PE and PA could assist in the removal of P and NH4+ from contaminated water using BC.

Mathematical-Based CFD Modelling and Simulation of Mushroom Drying in Tray Dryer

In this study, CFD simulations that incorporate the inherent coupling between the moisture content of the mushroom and hot air flow in the tray dryer were performed. Conservation principles were applied to the fundamental quantities of mass, momentum, and heat. The source terms due to the moisture evaporation, the viscous and inertial resistance, and continuous evaporative cooling were determined through experimental results. Experiments were conducted to study and select the drying kinetics model at the optimum drying conditions and moisture sorption isotherm model at 30, 40, and 50°C temperatures. The best model describing the drying kinetics of mushrooms and moisture sorption isotherm model was chosen based on the lowest RMSE values and the highest R 2 value. Midilli et al.’s drying kinetics model and the modified Henderson sorption isotherm model were adopted in CFD modelling. The CFD software ANSYS Fluent was used for the 3D modelling of mushroom drying in a tray dryer. The mass and energy source term equations were added to the ANSYS Fluent software using a user-defined function (UDF). The parameter permeability of medium ( α ) and pressure-jump coefficient ( C 2 ) appearing in the momentum source term were directly introduced in the Fluent setup as cell zone conditions. The simulation results of the moisture removal and drying temperatures were validated against experimental data. Both results are in good agreement with the experimental data, with R 2 values of 0.9906 for moisture contents and 0.926 for drying temperature. Thus, simulation can be an option to study the drying mechanisms and alleviate some drawbacks of doing experiments.

Green synthesis of sustainable magnetic nanoparticles Fe3O4 and Fe3O4-chitosan derived from Prosopis farcta biomass extract and their performance in the sorption of lead(II)

The sustainable processes are now in tremendous demand for nanomaterial synthesis as a result of their unique properties and characteristics. The magnetic nanoparticles comprised of Fe3O4 and its conjugate with abundant and renewable biopolymer, chitosan, were synthesized using Prosopis farcta biomass extract, and the resulting materials were used to adsorb Pb (II) from aqueous solution. Thermodynamic parameters revealed that the sorption of lead (II) on Fe3O4 as well as Fe3O4-Chitosan (Fe3O4-CS) has been an endothermic and self-regulating procedure wherein the sorption kinetics was defined by a pseudo-second-order pattern and the sorption isotherms corresponded to the Freundlich pattern. A multivariable quadratic technique for adsorption process optimization was implemented to optimize the lead (II) adsorption on Fe3O4 and Fe3O4-chitosan nanoparticles, the optimal conditions being pH 7.9, contact time of 31.2 min, initial lead concentration of 39.2 mg/L, adsorbent amount of 444.3 mg, at a 49.7 °C temperature. The maximum adsorption efficiencies under optimal conditions were found to be 69.02 and 89.54 % for Fe3O4 and Fe3O4-CS adsorbents, respectively. Notably, Fe3O4 and Fe3O4-CS can be easily recovered using an external magnet, indicating that they are a viable and cost-effective lead removal option.

Exploring the high activity of hierarchical copper oxide nanomaterials: Unveiling the influence of reduced size and enhanced surface area

The development of 3D hierarchical architectures composed of nanometer-sized primary building blocks holds great promise for a wide range of applications. Here, we present a simple synthesis method for hierarchical CuO nanomaterials. HRTEM images revealed that the CuO nanoparticles had a diameter of 4–6 nm and were aggregated to form a hierarchical rod-like morphology. Nitrogen sorption isotherm indicated that the samples possessed high surface areas (125–190 m2/g). The obtained CuO nanomaterials demonstrated remarkable catalytic activity in the reduction of methyl orange, methyl red, and 4-nitrophenol. Furthermore, the CuO nanomaterials exhibited excellent recycling ability, making them highly favorable and efficient catalysts.

Effect of biosolid-derived dissolved organic matter on orthophosphate sorption to soils depends on clay mineralogy and solution composition.

Dissolved organic matter (DOM) from biosolids can alter the sorption of orthophosphate (inorganic phosphorus (IP)) to soils and, therefore, affect the bioavailability of IP. It is not clear how clay mineralogy and solution composition interfere with DOM effects on IP sorption by soils. Hence, we studied the effect of DOM on IP sorption to five semi-arid soils dominated by either illite/smectite (I/S) or kaolinite clays. IP sorption isotherms were constructed in either NaCl or CaCl2 background solution, with and without the addition of DOM. The IP sorption capacity maxima (SMAX, Langmuir model) of the I/S soils were 33-102% higher in the presence of CaCl2, as compared to NaCl. Although DOM had no effect on the IP-SMAX in the presence of CaCl2, it increased the IP-SMAX by 35-59% in the presence of the NaCl solution. Surprisingly, DOM sorption to the I/S soils was 30-90% greater in the presence of a Na+-dominated solution, as compared to a Ca2+-dominated solution. In contrast to the I/S soils, the SMAX of the kaolinitic soil was not affected by the background electrolyte (Na+, Ca2+) or the addition of DOM. Furthermore, the addition of IP reduced the sorption of DOM to the kaolinitic soil (by up to 50%) in both background electrolyte solutions. These results highlight the contrasting roles of divalent and monovalent cations in conjunction with DOM in IP sorption to semi-arid I/S soils. We propose a new approach based on two conceptual mechanisms to explain the DOM's enhancement of IP sorption to I/S soils. (1) Under dispersion conditions in the Na+-dominated solutions, Ca2+-mediated DOM-IP complexes bind to the clay's negative planar surfaces. (2) Under flocculation conditions in the Ca+-dominated solutions, the distance between adjacent platelets decreases, reducing both the electronegative charge spillover and Ca2+ bridge-mediated DOM sorption. In contrast, the addition of DOM to kaolinite, a multi-platelet clay with a low isomorphic negative charge, reduces IP sorption due to competitive sorption on the clay's broken edges.

Rapid screening of gas solubility in ionic liquids using biased particle insertions with pre-sampled liquid trajectories

ABSTRACTWe present an efficient, general-purpose variant of the Widom test particle insertion method for computing chemical potentials of gaseous solutes in fluids or porous solids. The method is implemented in the Monte Carlo molecular simulation engine Cassandra, but receiving phase configurations are independent of this process and may be pre-sampled by other molecular simulation engines such as molecular dynamics codes. Efficiency enhancements present in this method include configurational biasing and accelerated atomic overlap detection. When applied to the estimation of Henry's law constants of atomistic difluoromethane and pentafluoroethane in ionic liquids, the accelerated overlap detection results in a speedup of more than an order of magnitude compared to conventional methods without sacrificing accuracy. We found good agreement between this method and Hamiltonian replica exchange (HREX) for Henry's law constant and absorption isotherm estimation. This embarrassingly parallel method is especially well suited for screening Henry's law constants of many small gases in the same solvents, since a liquid trajectory can be reused for as many solutes as desired.

Environmental fate and metabolic transformation of two non-ionic pesticides in soil: Effect of biochar, moisture, and soil sterilization

Soil moisture, organic matter, and soil microbes are the key considering factors that control the persistence, degradation, and transformation of applied pesticides under varied soil conditions. In this study, underlying influence of these factors was assessed through the fates and metabolic transformation of two non-ionic pesticides (e.g., Phorate and Terbufos) in soils. Concisely, two distinct experiments including a customized batch equilibrium (sorption study), and a lab incubation trial (degradation study) were performed, following the OECD guidelines. As per study findings, biochar (BC) amendment was found to be the most influential factors during sorption study, particularly, 1% BC amendment contributed to achieve the best results. In addition, the non-linearity of sorption isotherm (1/n < 1.0) was revealed through Freundlich isotherm, indicating the strong adsorption of studied pesticides onto the soils. On the other hand, during degradation study, soil moisture initiates the enhanced degradation of parent pesticides and subsequent metabolism. In the presence of 40% water holding capacity (WHC), 1% BC amendment enhances the metabolic transformation, while H2O2 treatment could hinder the process. Additionally, the half-life degradation (t1/2) of phorate and terbufos was controlled by biochar amendment, moisture, and soil sterilization, respectively. Finally, BC can accelerate the metabolic transformation, whereas, phorate underwent a metabolic change into sulfoxide and sulfone while terbufos turned into solely sulfoxide. This pioneering study gathered crucial data for understanding the persistence and metabolic transition of non-ionic pesticides in soils and their patterns of degradation.

Brewers spent grain drying: Drying kinetics, moisture sorption isotherms, bioactive compounds stability and Bacillus cereus lethality during thermal treatment.

The most abundant by-product of the brewing industry is beer bagasse (BSG); its high moisture content requires a rapid drying process to stabilize the product. The objective of this work was to carry out the analysis and mathematical modeling of the drying process of thin layer bagasse at temperatures above 60 °C in order to establish adequate processing conditions that assure its safe use and storage as a functional ingredient. The moisture sorption isotherms of BSG were determined at 10, 20 and 40 °C. Considering the most unfavorable condition tested (40 °C), the maximum residual moisture content that avoids the growth of Bacillus cereus was 15% dry basis, that corresponds to aw = 0.93. The drying curves of thin layers of BSG were obtained experimentally and mathematically modeled using Fick's law; lethality to achieve at least a 2-log reduction in Bacillus cereus population was assessed in terms of thermal inactivation kinetic parameters. Drying conditions at temperatures above 75 °C with air velocity of 3.2 m/s, increased total phenol content levels enhancing antioxidant activity.

Porous Core-membrane Microstructured Nanomaterial Composed of Deep Eutectic Solvents and MOF-808 for CO2 Capture.

A series of porous core-membrane microstructured nanomaterials, constructed of a deep eutectic solvent (DES) membrane and porous MOF-808 core via liquid surface tensions and electrostatic interactions, are introduced for carbon dioxide capture with the sorption mechanism coupling diffusion, physisorption, and chemisorption. MOF-808 as the porous core considerably improves the diffusion interactions for DES membranes, hence significantly enhancing the sorption performance of DESs. Although the DES consisted by monoethanolamine and tetrapropylammonium chloride (MEA-TPAC-7) has the highest sorption capacity among all DESs, it is only 4.39 mmol g-1 at 2.4 bar and further attenuates by fastidious diffusion interactions when increasing viscosity or dose. The sorption capacities of DES@MOF-120 are 5.18 mmol g-1 at 3.0 bar and 4.78 mmol g-1 at 2.4 bar without apparent sorption hysteresis in pressure swing sorption, which are substantially improved contrasted to MEA-TPAC-7. The sorption isotherms are reconstructed via Sips models considering surface heterogeneity with regression correlation coefficients over 0.9454 to forecast maximum sorption capacity over 6.33 mmol g-1 .

Multivariate Hydrogen‐Bonded Organic Frameworks with Tunable Permanent Porosities for Capture of a Mustard Gas Simulant

AbstractPrecise synthesis of topologically predictable and discrete molecular crystals with permanent porosities remains a long‐term challenge. Here, we report the first successful synthesis of a series of 11 isoreticular multivariate hydrogen‐bonded organic frameworks (MTV‐HOFs) from pyrene‐based derivatives bearing −H, −CH3, −NH2 and −F groups achieved by a shape‐fitted, π–π stacking self‐assembly strategy. These MTV‐HOFs are single‐crystalline materials composed of tecton, as verified by single‐crystal diffraction, nuclear magnetic resonance (NMR) spectra, Raman spectra, water sorption isotherms and density functional theory (DFT) calculations. These MTV‐HOFs exhibit tunable hydrophobicity with water uptake starting from 50 to 80 % relative humidity, by adjusting the combinations and ratios of functional groups. As a proof of application, the resulting MTV‐HOFs were shown to be capable of capturing a mustard gas simulant, 2‐chloroethyl ethyl sulfide (CEES) from moisture. The location of different functional groups within the pores of the MTV‐HOFs leads to a synergistic effect, which resulted in a superior CEES/H2O selectivity (up to 94 %) compared to that of the HOFs with only pure component and enhanced breakthrough performance (up to 4000 min/g) when compared to benchmark MOF materials. This work is an important advance in the synthesis of MTV‐HOFs, and provides a platform for the development of porous molecular materials for numerous applications.

Multivariate hydrogen-bonded organic frameworks with tunable permanent porosity for a mustard gas simulant capture.

Precise synthesis of topologically predictable and discrete molecular crystals with permanent porosities remains a long-term challenge. Here, we report the first successful synthesis of a series of isoreticular multivariate hydrogen-bonded organic frameworks (MTV-HOFs) from pyrene-based derivatives bearing -H, -CH3, -NH2 and -F groups achieved by a shape-fitted, π-π stacking self-assembly strategy. These MTV-HOFs are single-crystalline materials composed of tectons with as many as 4 different functionalities, verified by single-crystal diffraction, nuclear magnetic resonance (NMR) spectra, and Raman spectra. These MTV-HOFs exhibit tunable hydrophobicity with water uptake starting from 50 to 80% relative humidity, by adjusting the combinations and ratios of functional groups. As a proof of application, the resulting MTV-HOFs were shown to be capable of capturing a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES) from moisture. The location of different functional groups within the pores of MTV-HOFs leads to a synergistic effect, which resulted in a superior CEES/H2O selectivity (up to 94%) to that of the HOFs with only pure component and enhanced breakthrough performance (up to 4000 min/g) when compared to benchmark MOF materials. The synthesis of MTV-HOFs provides a platform for the development of porous molecular materials for numerous applications.

Cesium transport in Czech compacted bentonite: Planar source and through diffusion methods evaluated considering non-linearity of sorption isotherm

The aim of the presented study was to determine the influence of non-linear character of Cs sorption isotherm and dominant interlayer cation on the sorption and diffusion properties of the Czech compacted bentonite. Planar source and through diffusion experiments with Cs on the compacted bentonite were performed and evaluated by suitable methods accounting for the transient state of diffusion and the presence of separating filters. It was shown that the observed Cs concentration profiles can be appropriately simulated with the use of Langmuir isotherm. The fitted values of sorption parameters obtained from the evaluation of through diffusion experiments generally agreed with the values expected from the batch sorption experiments. The most important factor for the Cs diffusion was its total concentration in the experiment with Da values ranging from about 1⨯10−13 m2·s−1 at the Cs concentration 10−7 M to about 4⨯10−12 m2·s−1 at the Cs concentration 10−3 M. The observed discrepancies between the experimental data and the standard model based on Fickian diffusion were explained by the application of dual transport model using so-called surface diffusion theory. The importance of surface diffusion in through diffusion experiments increased with increasing Cs total concentration, which indicates that this effect is probably connected to the ion exchange mechanism on layer sites of bentonite.

Effect of Germinated Sorghum Extract on the Physical and Thermal Properties of Pre-Gelatinized Cereals, Sweet Potato and Beans Starches.

Starches from different botanical sources are affected in the presence of enzymes. This study investigated the impact of α-amylase on several properties of pre-gelatinized starches derived from chickpea (Cicer arietinum L.), wheat (Triticum aestivum L.), corn (Zea mays L.), white beans (Phaseolus vulgaris), and sweet potatoes (Ipomoea batatas L.). Specifically, the water holding capacity, freezable water content, sugar content, and water sorption isotherm (adsorption and desorption) properties were examined. The source of α-amylase utilized in this study was a germinated sorghum (Sorghum bicolor L. Moench) extract (GSE). The starch samples were subjected to annealing at temperatures of 40, 50, and 60 °C for durations of either 30 or 60 min prior to the process of gelatinization. A significant increase in the annealing temperature and GSE resulted in a notable enhancement in both the water-holding capacity and the sugar content of the starch. The ordering of starches in terms of their freezable water content is as follows: Chickpea starch (C.P.S) > white beans starch (W.B.S) > wheat starch (W.S) > chickpea starch (C.S) > sweet potato starch (S.P.S). The Guggenheim-Anderson-de Boer (GAB) model was only employed for fitting the data, as the Brunauer-Emmett-Teller (BET) model had a low root mean square error (RMSE). The application of annealing and GSE treatment resulted in a shift of the adsorption and desorption isotherms towards greater levels of moisture content. A strong hysteresis was found in the adsorption and desorption curves, notably within the water activity range of 0.6 to 0.8. The GSE treatment and longer annealing time had an impact on the monolayer water content (mo), as well as the C and K parameters of the GAB model, irrespective of the annealing temperature. These results can be used to evaluate the applicability of starch in the pharmaceutical and food sectors.

Performance expectation of coal waste in permeable reactive barrier for removal of cadmium considering contamination level and pore water velocity

The effectiveness and longevity of permeable reactive barriers (PRBs) depend on the performance of the reactive materials and the subsurface environment. The relationship of the groundwater velocity on performance of coal waste for the heavy metal removal was reported in our previous study. In this study, we investigated the performance and longevity of coal waste as a PRB material for the removal of Cd considering subsurface environmental conditions such as contamination level and groundwater velocity. The artificial groundwater contaminated by Cd were prepared with various concentrations ranging from 10 to 100 mg L−1. Lab-scale column experiments were conducted using coal waste filled columns by injecting the artificial groundwater. The breakthrough curves were analyzed advection dispersion equation coupled with equilibrium sorption model to determine the retardation factor. The Cd breakthrough curves exhibited different retardation with respect to the contamination levels. The Cd transport was more retarded as the contamination level lowered. The relationship between the retardation factor and the contamination levels could be explained with empirical equations based on non-linear sorption isotherms. By adopting the velocity dependency of sorbent performance in our previous study, transport of Cd within coal waste was simulated under various subsurface environmental conditions to construct the longevity function. The function could be used for the longevity prediction of coal waste as a PRB material considering groundwater velocity and contamination level in subsurface environment.

Desorption and Sorption Isotherms of Different Varieties of Hemp Seeds with Different Percentages of Dockage under Different Temperatures and Different Relative Humidities

Hemp cultivation faces challenges due to the adoption of dioecious cultivars, which suffer from biomass loss and fibre heterogeneity. In contrast, monoecious cultivars offer simultaneous fibre and seed production, albeit with lower fibre quality. Understanding the drying characteristics and storage requirements of hemp seeds is crucial for effective post-harvest management. This study explored the moisture sorption and desorption isotherms of two common Canadian hemp seed varieties, Altair (dioecious) and CanMa (monoecious), by using both saturated salt solution (SSS) and thin-layer drying methods. Their isotherms were also compared with the published isotherm of Finola—a common dioecious variety in Europe. The thin-layer drying method yielded higher EMC values than the SSS method due to incomplete equilibrium attainment. Larger EMC differences existed between different seed types (dioecious vs. monoecious), and this difference was small between the same seed types (dioecious vs. dioecious). The GAB equation provided the most accurate prediction of equilibrium moisture contents for both varieties.

Stabilization of hydrophobic organic compounds in sediment using alkali-activated rice husk biochar: Enhancement of sorption by dissolved organic matter

Polycyclic aromatic hydrocarbons and phthalate esters are hydrophobic organic compounds (HOCs) that pose strong risks to aquatic and sediment ecosystems. The aim of this study was to develop a material for stabilizing (sorbing) HOCs in contaminated sediment. Activated biochar with a high surface area (called RH–NaOH) was successfully synthesized by activating rice husk biochar with an alkali (NaOH). The kinetics of HOC sorption to the RH–NaOH were described well by a three-stage intraparticle diffusion model. The sorption isotherms were adequately described by the Sips sorption model. The presence of dissolved organic matter (DOM) at environmentally relevant concentrations enhanced HOC sorption to the RH–NaOH by as much as a factor of 10, and this was mainly caused by the fulvic-acid- and humic-acid-like fractions of the DOM. The degree of sorption enhancement was predicted by the integrated volume of the fulvic-acid- and humic-acid-like fraction regions of the excitation–emission matrix that was used to characterize the DOM. The polycyclic aromatic hydrocarbon and phthalate ester stabilization efficiencies when 150 d was allowed for equilibration between the sediment and RH–NaOH to be reached were 96.5% and 94.6%, respectively. The stabilization tests indicated that HOC sorption proceeded via multiple stages with different kinetics. These stages were attributed to complex processes involving HOC and DOM sorption and desorption, HOC–DOM interactions, and HOC and HOC–DOM mixture diffusion into pores. The RH–NaOH has great potential for use as a sorbent for stabilizing HOCs in contaminated sediment.