BET Model Research Articles

Vitamin B Complex Encapsulation in Bacterial Nanocellulose: A Novel System for Heat and Chemical Stabilization in Food Products.

Bacterial nanocellulose has been commonly used as a gelling or stabilizing agent in the food industry and as an excipient in pharmacology. However, due to its physical and chemical properties, such as its high degradation temperature and the ease with which it can interact with other molecules, bacterial nanocellulose has been established as a material with great potential for the protection of bioactive compounds. This research shows the capacity of bacterial nanocellulose to establish interactions with B vitamins (B1, B2, B3 and B12) through different sorption isotherms, mainly by means of the BET, GAB and TSS models. First, the degradation of the vitamin B complex, which mostly occurs upon heating, is minimized in the presence of BNC, herein proposed as a thermal stabilizer. Secondly, BNC is shown to bind to micronutrients and act as dietary fiber. BNC acts as a thickening and water-binding agent. The effects of BNC are determined to occur as an encapsulation system that facilitates affinity adsorption in mono- and multilayers. Finally, bacterial nanocellulose was used as an encapsulating agent for the vitamin B complex by spray drying. It is demonstrated that BNC is a very successful new nanomaterial for encapsulation, with a high level of adsorption, and for the protection of hydro-soluble vitamins. BNC has shown great potential to adsorb vitamins B1, B2, B3 and B12 owing to their hydroxyl groups, which are responsible for its water or vitamin sorption. Due to the features of bacterial nanocellulose, it is possible to use it as a raw material in the food industry to protect micronutrients during the thermal process.

Corrosion-life prediction model for 316L stainless steel under electronic special gases containing trace moisture employed in semiconductor manufacturing industry

Special gases with trace moisture cause the formation of dynamic acidic microdroplets (DMD), which results in corrosion of semiconductor manufacturing devices. In this study, a predictive model for corrosion damage in 316L stainless steel (SS) was developed by combining the DMD process and the pitting initiation model. The DMD process was modeled using the BET model to describe the moisture-to-solution conversion. The pitting initiation model was reconstructed by incorporating the Sridhar model, temporal corrosion model, and Macdonald model. Finally, the predicted results were validated by various experimental data, indicating that the prediction model was accurate and highly reliable.

Kinetic, equilibrium, and thermodynamic aspects of phenol adsorption onto acrylonitrile-divinylbenzene copolymer

Adsorption of phenol onto acrylonitrile-divinylbenzene copolymer (AN-DVB) was comprehensively investigated with the aspect of kinetic, equilibrium, and thermodynamic. The effect of adsorbent dosage, initial concentration, temperature, and pH were studied in batch adsorption process. Maximum phenol adsorption capacity was obtained at neutral pH of phenol solution (6.8), at room temperature (25 °C) and at higher initial concentrations (500 mg/L) as 117 mg/g. After examining two-parameter- and three-parameter-adsorption-isotherm models, experimental data were represented well by using Freundlich adsorption isotherm model at neutral pH. Due to the all possible interactions like hydrogen bonding, π-π stacking and hydrophobic ineractions have different strengths and energetic values, phenol adsorption at neutral pH (6.8) exhibited a heterogeneous multilayer process. On the other hand, Langmuir and BET models well represented the experimental data obtained beyond neutral pH due to the weakening of different interactions, hence, multilayer but more uniform adsorption occurred. Phenol adsorption followed pseudo-second-order kinetic model that shows the surface interactions play significant role on the adsorption rate. Analysis of Boyd's intraparticle and external diffusion kinetic models indicated that in addition to surface interactions, diffusion also controlled the adsorption rate at room temperature. Activation energy was calculated as 92.99 kJ/mol, which shows the strong interaction between phenol and AN-DVB. Adsorption enthalpy change and entropy change was calculated as −25.731 kJ/mol and −0.041 kJ/molK, respectively. Thermodynamic parameters indicated that adsorption process was exothermic and spontaneous in nature.

Removal of Lead Cations by Novel Organoclays Derived from Bentonite and Amphoteric and Nonionic Surfactants.

For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested as effective sorbents for lead ions. The maximum values of R were obtained when describing the sorption processes using the Langmuir model, which ranged from 0.97 to 0.99. The adsorption of lead ions by these organoclays was investigated using different sorption models including the Langmuir, Freundlich, and BET. It was found that, according to the values of limiting adsorption to the Langmuir equation, the synthesized organoclays formed an increasing series: organoclay with cocamide diethanolamine < bentonite < organoclay with lauramine oxide < organoclay with sodium cocoiminodipropionate < organoclay with disodium cocoamphodiacetate < organoclay with alkyl polyglucoside. The Gibbs energy for all of the analyzed samples was calculated and found to be negative, indicating the spontaneity of the cation adsorption process in the forward direction. The maximum value of the adsorption capacity of lead cations on organoclay-based bentonite with alkyl polyglucoside was 1.49 ± 0.05 mmol/g according to the Langmuir model, and 0.523 ± 0.003 mmol/g as determined by the BET model. In the process of modifying bentonite, there was an increase in negative values of the zeta potential for organoclays compared to the initial mineral, which clearly enhanced their electrostatic interactions with the positively charged lead ions. It was hypothesized, based on the physicochemical principles, that exchange adsorption is the main mechanism for lead absorption. Based on chemical approaches, organoclays based on amphoteric surfactants absorb lead mainly through the mechanisms of electrostatic attraction, ion exchange, and complexation as well as the formation of insoluble precipitates. Organoclays based on nonionic surfactants, on the other hand, absorb lead through mechanisms of complexation (including chelation) and the formation of insoluble chemical precipitates. The comparison of isotherms from different models allows us to find the most accurate match between the model and the experimental data, and to better understand the nature of the processes involved.

Use of Chitosan-Iron Oxide Gels for the Removal of Cd2+ Ions from Aqueous Solutions.

High-quality water availability is substantial for sustaining life, so its contamination presents a serious problem that has been the focus of several studies. The presence of heavy metals, such as cadmium, is frequently studied due to the increase in the contamination levels caused by fast industrial expansion. Cadmium ions were removed from aqueous solutions at pH 7.0 by chitosan-magnetite (ChM) xerogel beads and chitosan-FeO (ChF) xerogel beads in batch systems. Kinetic studies were best modeled by the Elovich model. The adsorption isotherms obtained showed an inflection point suggesting the formation of a second layer, and the BET model adjusted to liquid-solid systems was adequate for the description of the experimental data. Maximum uptake capacities of 36.97 ± 0.77 and 28.60 ± 2.09 mg Cd/g xerogel were obtained for ChM and ChF, respectively. The studied composites are considered promising adsorbent materials for removing cadmium ions from aqueous systems.

Polycyclic aromatic hydrocarbon derivatives onto polar microplastics of polyurethane: equilibrium, thermodynamics, and kinetics of monolayer-multilayer adsorption.

The study of the adsorption of polycyclic aromatic hydrocarbons on microplastics (MPs) has attracted much attention as to how microplastics can act as carriers of these pollutants. Polyurethane (PU) is one of the MPs found in aquatic environments, containing different functional groups it can interact with polar and nonpolar molecules. PAH derivatives (dPAHs) present different properties and thus can be adsorbed by different interactions; thus, this study investigated the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran (DBF), and carbazole (CBZ) onto PU MP. The Langmuir, Freundlich, and BET isotherm models were examined, and the BET model best fitted. The adsorption was a nonspontaneous process, exothermic for mono- and multilayer formation for FLN, DBT, and CBZ, and endothermic for DBF monolayer formation. The adsorption monolayer was formed by van der Waals forces, H─bonding, and π─π interactions, while the formation of the multilayer can be explained by π─π and hydrophobic interactions. The pseudo-second-order model proved to be more consistent for the adsorption of dPAHs. The adsorption in artificial seawater shows no significant differences for the monolayer but favored the adsorption multilayer due to the salting-out effect. Due to the existence of several adsorption mechanisms, PU MP interacts with dPAHs in greater quantities when compared to a MP with a simpler structure.

Study of moisture sorption thermodynamic in canola oilseed and drying energy requirement considerations

AbstractThe objective of this study is to derive the thermodynamic characteristics from sorption isotherm data for canola. The semi‐gravimetric method was utilized at three different temperatures (25, 40, and 55°C) and seven air relative humidity levels within the range of 11%–90%. The observed data indicated that the equilibrium moisture content of the sample decreased as the temperature increased. The “GAB and BET” models were applied to fit the empirical data, which demonstrated a Type III isotherm, and the monolayer water content was subsequently determined using these models. Thermodynamic properties such as “isosteric heat,” “net isosteric heat,” “differential entropy,” “net integral entropy,” and “net integral enthalpy” were determined from isothermal sorption curves. The results show that as moisture content increases, both the sorption isosteric heat and the differential entropy of sorption decrease. This indicates that at higher moisture levels, the energy required for additional moisture adsorption and the changes in entropy are reduced. Similarly, the net isosteric heat of sorption and the net integral enthalpy of sorption also decrease with increasing moisture content, consistent with the observed reductions in isosteric heat and differential entropy. The specific absorption surface area for each temperature was determined by calculating the monolayer moisture content using both the “GAB and BET models.” The net integral entropy had an increasing trend in the range of 4%–4.5% (db%), while it decreased in the range of 4.5%–6.8% of moisture content. In addition, the spreading pressure at three levels of temperature was reported. Finally, an empirical relation was employed to illustrate the cumulative energy requirement for drying versus moisture content. The results indicated that at low moisture content levels, the drying process required significantly higher energy.Practical applicationsMoisture sorption isotherms are essential for understanding the interaction between water and food ingredients. This knowledge is vital for improving food processing methods such as drying, mixing, cooling, and storage. In industry, isotherms can help determine the best drying method to maintain food quality, identify the optimal mixing conditions to ensure consistency, establish cooling protocols to prevent spoilage, and set storage guidelines to extend shelf life. In addition, understanding thermodynamic properties is crucial for regulating moisture absorption and release, achieving the desired food texture, managing surface characteristics, and calculating the energy needed for effective dehydration processes.

Investigating the Mechanisms of Discoloration in Modern Dental Materials: A Comprehensive Characterization Approach.

In general, patients' opinions on reaching ideal esthetics while restoring dental tissues is one of the most important part of the oral treatment. Unfortunately, discoloration of dental materials may occur due to intrinsic and extrinsic factors. The aim of the study was to evaluate the color stability of frequently used dental resin materials and determine the mechanism of their discoloration. The study used various characterization techniques (optical microscopy, Fourier-transform infrared spectroscopy, low-temperature N2 adsorption, diffuse reflectance spectroscopy, and luminescence) to understand the effect of surface defects on discoloration. The adsorption of model liquids on the surface was confirmed to be related to the increase in BET surface area. The study found that the adsorption of discolorants, such as coffee, tea, and wine, on the surface of the dental material follows the multilayer BET model. When the surface is smooth, the discoloration is usually within acceptable limits, with a maximum of ∆E = 3.3. The discoloration made by tea and demineralized water was within acceptable limits even after 7 days of exposure.

Preparation and characterization of Ea-AgNPs-Si nanocomposite: investigating it as a poultry reformer, pathogen suppressor, sprouting catalyst and adsorbent

This study synthesizes nano composite (Ea-AgNPs-Si) using Euphorbia antisyphilitica(Ea), employing it as a poultry reformer, sorptive material, pathogen suppressor and sprouting catalyst. Characterization involved XRD, SEM, TEM, Zetasizer, UV-Visible and FT-IR techniques. Ea-AgNPs-Si adopted a face centered cubic arrangement with average crystalline size of 20.34 nm. Zeta potential assessed stability. PDI value of Ea-AgNPs-Si nanocomposite is 1 indicating the polydisperse distribution. SEM revealed flower shape (Ea-AgNPs-Si), ranging 70-100 nm in diameter. The disc diffusion method reveals that EaAgNPs-Si exhibits potent antimicrobial activity at 60 µl against Staphylococcus aureus, Actinomycetes, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa, attributed to its deep diffusion and release of silver ions and silica. It is unequivocally evident from the data that Langmuir isotherm and Pseudo II order model provides a superior fit approaching R2 value as 0.9972, 0.9461, 0.916, 0.9827, 0.9455 and 0.9534 for LA(I), LA(II), LA(III) describing monolayer chemisorption onto surfaces with uniform adsorption energies than Freundlich, Tempkin and BET models, which is synonymous with the results obtained from R2011a Matlab neuro solution. Through final germination (FG) we concluded that among 130 corriandrum seeds sown,109 sprouted in 20 days. Higher germination index (GI) T2&gt;T4&gt;T1&gt;T3&gt; expedited that Ea-AgNPs-Si shall be used as a nutrient to boost the growth of crops. Ordinarily, it necessitates a span of 45 days for a single batch to attain harvest readiness; however, through our efforts, we have accomplished this feat in a mere 20 days. Henceforth, Ea-AgNPs-Si shall be employed as a Poultry Reformer, Pathogen Suppressor, Sprouting Catalyst and Adsorbent.

Electroadsorption of La3+ and Ce3+ from aqueous media with a carbon paste electrode modified with HMS-CMPO

This work deals with the electroadsorption of rare earths cerium and lanthanum in aqueous solution by using a carbon paste electrode modified with a silica mesoporous material functionalized with carbamoyl methyl phosphine oxide (CMPO). This functionalization was carried out in a two-step synthesis, the intermediate product was synthesized by attaching N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (APTMS) to the surface of the HMS by a grafting method synthesis, then this intermediate was modified by CMPO, in a further condensation reaction. The final product CMPO obtained was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermal gravimetric analysis (TGA) and N2 adsorption/desorption isotherms using BJH and BET models. Showing thermal stability, a surface area higher than 450m2g-1 and mesoporous properties. The CMPO material was used to modify the mixture of the carbon paste electrode producing an enhancement in the interaction between the electrode surface and the lanthanides studied, at the same time it produces and improvement in the electroactive area by over two orders of magnitude. The modified carbon paste electrode (CMPO-CPE) developed in this work shows an increase in the conductivity, observed with the electrochemical impedance spectroscopy studies, and an increase in the electroactive area of 47 % was calculated from cyclic voltammetry experiments. CMPO-CPE was used to extract La3+ and Ce3+ from aqueous solution using NaNO3 as support electrolyte, by using a fixed potential program over time, measuring the obtained current by Chronoamperometric method. The adsorption and desorption results were corroborated with Inductively coupled plasma atomic emission spectroscopy (ICP-OES) demonstrated the capacity of extraction of the electrode were 74 μg after ten cycles for La3+ at pH 5.0 and 15 μg after ten cycles for Ce3+ at pH 6.0, using a CMPO modified electrode of small surface (3 mm radius). This electrode was tested for over 50 cycles without losing their electroactive properties under tested electrochemical conditions.

Facile synthesis of a novel, efficient, reusable inorganic adsorbent from volcanic rock powder wastes and its application for the removal of dyes and metals from water

A new, efficient, and reusable inorganic adsorbent (NP.F) was easily synthesized using volcanic rock powder wastes (NP) as a precursor, with the synthesis of NP.F carried out at 550 ºC and with a ratio of NaOH (alkalinizing) and sample NP equal to 1. The samples were used in batch adsorption to uptake Ag+(aq.), Cu2+(aq.), acid green 16 (AG 16), and acid red 97 (AR 97) from aqueous solutions at pH 6.53, 5.98, and 2.3, respectively. NP and NP.F were characterized by different analytical techniques, such as XRD, FTIR, BET, TGA/DTG, etc. The adsorption kinetic carried out at 298 K for dye solutions with concentrations ranging from 50 to 200 mg L−1 and metals from 10 to 100 mg L−1 showed that data fit the pseudo-second-order mathematical model with rapid sorption and process equilibrium was reached after 30 min for dyes and 40 min for metal ions. The Sips model proved adequate to represent the adsorption isotherms of metallic ions and the dye AR 97, while the BET model represented the isotherms of the dye AG 16. The NP.F sample showed notable adsorption capacity for all the contaminants studied; for example, the adsorption capacity of the dye AR 97 was 295 mg g−1, while that of the Ag+ ion was 93 mg g−1. Besides, the adsorption of Cu2+(aq.) ion, dyes AG 16, and AR 97 were endothermic, while the adsorption of Ag+(aq.) was exothermic. Furthermore, even after numerous subsequent adsorption cycles, the NP.F sample maintained a high reusability, suggesting that the sample is qualified to be an adsorbent for removing contaminants from liquid effluents. In conclusion, NP.F could be easily converted into an efficient inorganic adsorbent for colorants and metals.

New insight into CH4 adsorption mechanism in coal based on modeling analysis of different adsorption theories

Based on the principle of Gibbs excess adsorption measurement, high-pressure isothermal adsorption and desorption experiments of CH4 were performed on fractured coal samples, and CH4 adsorption phase density was obtained by the intercept method according to the experimental data. The Langmuir model, BET model, DA model, and their corrected model, the supercritical adsorption models were used for the fitting analysis of CH4 excess adsorption capacity. A hybrid model of different adsorption theories was developed based on CH4 adsorption phase density and theoretical adsorption capacity predicted by the intercept method. The transition in the occurrence pattern and control mechanism of CH4 in coal were investigated. The fitting of the Langmuir model, BET model, DA model, and their corrected models, the SBET model, the SDA model, and the SDA-L model to the CH4 excess adsorption capacity in coal shows that all multilayer adsorption theory model is not suitable for fitting the CH4 excess adsorption capacity in coal. The uncorrected Langmuir model and DA model are only suitable for fitting the CH4 excess adsorption capacity in coal in the low-pressure stage (pressure below 10 MPa). The corrected Langmuir model, the corrected DA model, the SDA model, and the SDA-L model can be used to fit the CH4 excess adsorption capacity in coal, but they show some bias in predicting the theoretical CH4 adsorption capacity and the CH4 adsorption phase density. The fitting of the three main adsorption theory models suggests that there may be simultaneous monolayer adsorption and microporous filling adsorption. The fitting results of the hybrid model based on monolayer adsorption and microporous filling adsorption theory depend on showing that with the increase of temperature, the occurrence of CH4 in coal gradually changes from mainly monolayer adsorption to mainly microporous filling adsorption, and the transformation of occurrence mode is related to temperature and the development of pores in coal.

Composite Coatings Applied to Fresh and Blanched Chayote (Sechium edule) and Modeling of the Drying Kinetics and Sorption Isotherms.

Sustainable methods such as convective drying have regained interest in reducing the loss and waste of food produce. Combined with techniques like blanching and edible coatings, they could serve as useful tools in food processing development. Composite coatings comprising pectin, soy protein isolate, and xanthan gum were optimized using response surface methodology with the Box-Behnken design. This optimization aimed to investigate their effects on the moisture content, water activity, total color, and rehydration ratio of fresh and blanched chayote slices. Additionally, the study explored the modeling of the drying kinetics and sorption isotherms of chayote (Sechium edule) slices. Soy protein and xanthan gum were found to primarily influence the moisture content (ranging from 5.44% to 9.93%), and pectin influenced water activity (033 to 0.53) of the fresh-coated chayote, while pectin affected the aw (2.13-8.28) and rehydration of the blanch-coated chayote. The optimized formulations for both fresh and blanched chayote were utilized to assess the drying kinetics behavior and sorption isotherms. The best fit (R2: 0.996 to 0.999) was achieved with the parabolic model for thin-layer materials. Furthermore, the sorption isotherms of chayote displayed a Type IV behavior, with the BET model being the most suitable for describing the sorption behavior of materials with low water activity. The predicted values offer valuable data for optimizing processing conditions to enhance the quality and stability of dried chayote.

Optimizing Activated Carbon Production from Waste Cashew Nut Shell with Zinc Chloride: A Box-Behnken Design and Group Method of Data Handling (GMDH) Application

In this study, Response surface methodology (RSM) and innovative Group Method of Data Handling (GMDH) approaches are applied to investigate the optimal process conditions of zinc chloride activated cashew nut production process. The effects of activation conditions (i.e. activation temperature, activation time, and impregnation ratio) on the achievable BET surface areas were studied with the aid of Box Behnken Design (BBD) and GMDH. Comparative analyses of RSM and GMDH-type neural models were further researched. During the process, the polynomial model equations developed were modified and fine-tuned to predict the highest BET surface area(s) using regression analysis and GMDH multi-layered iterative algorithm (MIA). Analysis of Variance (ANOVA) revealed that the significant factor(s) were impregnation ratio, impregnation ratio product, and the 2-way interactions (activation temperature and impregnation ratio) for ZnCl2 activated cashew nut shell. The best activation conditions for producing highest BET surface area of 504 m2.g-1 was activation temperature (873K), activation time (60 min), and impregnation ratio (1.50).The proposed GMDH-type BET model was ascertained to be the best model with average correlation coefficient (R) and root mean square error (RMSE) of 0.925 and 32.0 respectively. Sensitivity analysis conducted for GMDH-type neural network also revealed that the activation temperature and activation time with sensitivity values of 90.6% and 74.1% respectively were the most influential parameters in the basic (ZnCl2) activation process. The results of this study show that RSM and GMDH-type neural network could be applied as effective analytical tools for optimizing the ZCNS (zinc chloride-activated cashew nut shells) manufacturing process.

Removal of eutrophication agents from wastewater using glauconite-based sorbents

Excessive phosphorus and nitrogen in water and sediment may cause eutrophication, which poses a potential risk to drinking water safety and the sustainability of aquatic ecosystems. The research focuses on the removal of phosphates and ammonium ions from aqueous solutions using a new thermally and microwave-treated glauconite. The surface morphology of the samples was studied by SEM. BET surface area, pore volume, and pore size distribution were measured. Adsorption studies were carried out in static and dynamic conditions. The best fit for adsorption of both pollutants is given by the Langmuir-Freundlich and BET models. The calcined sample showed the lowest adsorption capacity for phosphate (1.78 mg/g) but the highest capacity for ammonium (20.67 mg/g). For the microwave-irradiated sample, the adsorption capacity for ammonium increases from 0.723 to 4.37 mg/g, while that for phosphate remains almost at the same level (101.21 mg/g). In dynamic conditions, phosphorus was most efficiently retained by natural glauconite (more than 60% retention rate), and ammonium nitrogen by glauconite that was thermally treated in a muffle furnace (more than 80% retention rate after 3 h).

Chemical Properties and Moisture Sorption Isotherm of Smoke- Dried Catfish (Clarias gariepinus) and Mackerel (Trachurus trachurus) Produced with a Modified Smoking Kiln: Application of Four Models to Sorption on Data

The effectiveness of a modified smoking kiln, the smoking quality, and the moisture sorption characteristics of smoked dried catfish and mackerel were all investigated in this study. Smoked dried catfish protein, ash, fat and moisture ranged between 73.37 and 73.80 %, 5.00 and 5.40% 10.30 and 11.05% and 8.05 and 8.12% respectively and for smoked dried mackerel 70.58 and 70.67%, 5.00 and 5.94%, 12.99 and13.15%, and 6.14 and 6.37% respectively, while the moisture sorption isotherm confirmed type III BET isotherm with marked hysteresis. Smoke dried catfish and mackerel's type III isotherm is as expected given that food items high in protein have been observed to display type III forms. For the Henderson, BET, GAB, and Oswin models, the values of the root means square ranged from 2.6 to 8.7, 4.6 to 9.1, 5.9 to 12.1, and 4.1 to 13.16, respectively. The coefficients of determination for these models ranged from 0.95 to 0.99, 0.93 to 0.96, 0.83 to 0.94, and 0.91 to 0.94. For catfish and mackerel, the isosteric heats of sorption for the adsorption and desorption pathways, respectively, were 4.55 and 1.22 kJ/mol and 4.07 and 1.10 kJ/mol, respectively. With an increase in temperature from 20 to 40 oC, the apparent sorbate surface area fell for catfish from 99.38 to 85.02 m2/g solid and for mackerel from 76.01 to 66.25 m2/g solid. The smoking kiln performed the basic tasks of smoking and drying the fishes very well, with high-quality nutrients.

Green synthesis of metal-organic framework materials MOF-199 and its adsorption of organic solvents gas

This study synthesized the copper benzene-1,3,5-tricarboxylate metal-organic framework (Cu-BTC) by the hydrothermal method in mixed solvent water/ethanol/PEG. The formed MOF-199 material has a uniform, sharp, octahedral crystal morphology with a 5 ÷ 8 µm size. The surface area of MOF-199 with the BET model is 1.360,76 m2/g. This material can adsorb volatile organic compounds with high capacity. The saturation adsorption capacity of MOF-199 with ethanol, acetone, benzene, toluene, and butyl acetate was 99,50; 86,80; 91,00; 79,00; 104,50 mg/g, respectively. The regenerative capacity of the material also showed that the material was resistant to volatile organic solvents when used 7 times in a row, only decreased under 10%.

ADSORPTION CAPACITY OF LEAF POWDER OF FRUIT TREES AND BERRY BUSHES ACCORDING TO SPECTROPHOTOMETRY DATA

The results of the study of the adsorption of methylene blue from aqueous solutions by the powder of the leaves of fruit trees and berry bushes are presented. The adsorption capacity was determined by the method developed for activated carbon. The suitability of the spectrophotometric analysis method for determining the adsorption capacity of leaf powder was confirmed by the results of linearity and repeatability assessment. The applicability of the Langmuir, Freundlich and BET models to describe experimental adsorption isotherms of methylene blue on a powder mixture of leaves with a particle size of 0.25 mm is analyzed. By comparing the correlation coefficients, it is shown that the Langmuir and BET model describe experimental data on dye adsorption on powder better than the Freundlich model. The values of adsorption constants for the Langmuir model (KL=1.17 l/mmol) and BET (KBET=319.75 g/mmol) were obtained using the graphical method. Among the studied fruit trees, cherry leaf powder had the greatest adsorption capacity (0.532±0.017 mmol/g), among berry bushes – aronia, blackcurrant and gooseberry leaf powder (0.529±0.002; 0.472±0.011 and 0.479±0.004 mmol/g). Based on a comparative assessment of the results obtained with the value of the adsorption capacity of activated carbon (0.704 mmol/g), a conclusion was made about the suitability of the powder of the leaves of fruit trees and berry bushes for the removal of methylene blue from aqueous solutions.

In Ukrainian

Regulation of enterohepatic circulation of bile acids in human body is actual task to overcome cardiovascular diseases. The aim of this work was to create biocompatible sorbents with improved sorption ability in relation to bile acids. Mesoporous organosilicas of MCM‑41 type with chemically grafted 3‑aminopropyl and steroid groups were obtained by sol‑gel condensation of tetraethyl orthosilicate and functional silanes in the presence of template cetyltrimethylammonium bromide. Porous structure of synthesized organosilicas was characterized by low‑temperature nitrogen adsorption–desorption and X‑ray diffraction analysis. Formation of typical for MCM‑41 hexagonal arrangement of cylindrical mesopores was confirmed. Structural parameters of synthesized silica materials were calculated. The influence of surface steroid groups on sorption ability of organosilicas was studied on example of bile salts (sodium cholate and taurocholate) in dependence of duration of contact, acidity of medium, and equilibrium concentration. Analysis of kinetic parameters of sorption estimated by Lagergren and Ho-McKey models confirms the proceeding of pseudo-second order process. The most effective sorption of sodium cholate and taurocholate was observed at pH ~ 5 and pH ~ 2, respectively, where the ovterlapping of pH regions of 3‑aminopropyl groups protonation and bile acids dissociation takes place. Analysis of experimentally obtained isotherms by use of Freundlich, Redlich‑Peterson, and BET models was carried out. It has been found that protonated amino groups are the main sorption centers of bile acids protolytic forms by synthesized aminosilica in pH range from 1 to 8. Introduction of steroid groups in surface layer at sol-gel synthesis leads to the increase of bile salts sorption due to the cooperative interactions with formation of supramolecular structures in the surface layer of organosilica. Obtained results prove prospects of usage of organosilica sorbents with surface steroid groups for regulation of bile acids content in human body.

Simultaneous adsorption-catalysis process for methylene blue removal using MOF-Fe/GNPs composites

In this study, graphene nanoplatelets (GNPs) were combined with iron-organic framework materials using the ultrasonic method in a water/ethanol solvent. The resulting composite material had a clear crystalline morphology with a size range of 200 to 400 nm. The MOF-Fe particle grew in a particular order on GNPs, forming a uniform structure. The XRD diagram confirmed the presence of GNPs and MOF-Fe, with peaks at 21.103o and 26.728o assigned to GNPs, and peaks at 5.423o and 11.015o typical for MOF-Fe. The BET model estimated the surface area of MOF-Fe/GNPs at 441 m2/g. The composite showed high efficiency in treating chromogenic organic compounds through simultaneous adsorption and photocatalysis. Specifically, the material achieved over 80% methylene blue removal via adsorption mechanism after 2 hours, and 100% removal with simultaneous adsorption-photocatalysis treatment mechanism.