Desorption Isotherms Research Articles

Nitrate removal from aqueous solution by glucose-based carbonaceous adsorbent: Batch and fixed-bed column adsorption studies

In the present study, the glucose-based carbonaceous adsorbent was prepared from glucose, melamine and urea by using ZnCl2 activation and heated at 550°C under N2 flow. The sample was treated for the 1st, 2nd and 3rd activation process, and they were characterized by N2 adsorption and desorption isotherms, elemental analysis and X-ray photoelectron spectroscopy (XPS). The results showed that the content of nitrogen increased and that of oxygen decreased with the increasing of the number of activation process. The adsorbent obtained after the 2nd activation showed the best adsorption properties and was used in batch and fixed-bed column adsorption studies. In batch adsorption experiments, we investigated the factors affecting nitrate adsorption such as initial concentration, solution pH, adsorption isotherms and adsorption kinetics. The isotherm data and kinetic data were fitted well to the Langmuir isotherm model and pseudo-second-order model, respectively, and the maximum adsorption capacity calculated by Langmuir model was 1.58 mmol/g at pH 3. The adsorption performance of the adsorbent in industrial application mode was also investigated by fixed-bed column experiments. The breakthrough time of the packed column was 160 min for the initial nitrate concentration of 200 mg/L at pH 3. The saturated column could be regenerated by 1 mol/L HCl and reused for at least 5 adsorption-desorption cycles. The column showed good adsorption performance in both coexisting ions solution and real contamination water.

Enhanced Mechanical and Thermal Properties of Polyimide Films Using Hydrophobic Fumed Silica Fillers.

Polyimide (PI) composite films with enhanced mechanical properties were prepared by incorporating modified fumed silica (FS) particles while preserving their optical and thermal characteristics. The PI matrix was synthesized using a fluorinated diamine, a fluorinated dianhydride, and a rigid biphenyl dianhydride via chemical imidization. Commercially available FS particles, including unmodified FS particles (0-FS) and particles modified with dimethyl (2-FS), trimethyl (3-FS), octyl (8-FS), octamethylcyclotetrasiloxane (D4-FS), and polydimethylsiloxane (PDMS-FS) were used. Scanning electron microscope images and nitrogen adsorption-desorption isotherms revealed well-defined porous structures in the FS particles. The water contact angles on the composite films increased compared to those of the pristine PI films, indicating improved water resistance. The PI/0-FS films exhibited a typical trade-off relationship between tensile modulus and elongation at break, as observed in conventional composites. Owing to the poor compatibility and agglomeration of the PDMS-FS particles, the PI/PDMS-FS composite films exhibited poor mechanical performance and diminished optical characteristics. Although the longer-chained FS particles (8- and D4-FS) improved the tensile modulus of the PI film by up to 12%, a reduction of more than 20% in toughness was observed. The PI composite films containing the methylated FS particles (2- and 3-FS) outperformed 8- and D4-FS in terms of mechanical properties, with PI/3-FS films showing an over 10% increased tensile modulus (from 4.07 to 4.42 GPa) and 15% improved toughness (from 6.97 to 8.04 MJ/m3) at 7 wt. % silica loading. Except for the PI/PDMS-FS composites, all composite film samples exhibited more than 86% transmittance at 550 nm. Regarding thermal properties, the glass transition temperature (Tg) and thermal stability remained stable for most composite films. In addition, PI/3-FS films demonstrated enhanced dimensional stability with lower coefficients of thermal expansion (from 47.3 to 34.5 ppm/°C). Overall, this study highlights the potential of incorporating specific modified FS particles to tailor the mechanical, optical, and thermal properties of PI composite films.

Experimental study on modified lotus stem biochar-based catalysts for heavy oil aquathermolysis

To obtain high-activity catalysts for aquathermolysis at low temperatures, a composite modification method of KOH and silane coupling agent KH570 was used to successfully prepare modified lotus stem biochar (MLSB), and six catalysts with different ZrO2 and MoO3 contents (5–30 %) were synthesized by impregnation method. MLSB and catalysts were analyzed by SEM, N2 adsorption and desorption isotherms, surface pore size, and FT-IR. The results revealed that the pores of raw lotus stem biochar were increased and enlarged, and some -OH on the surface was replaced by hydrophobic groups to form hydrophobic supports. Catalysts had hydrophobic and strong acidic sites. The catalytic activities were evaluated by aquathermolysis experiments. Catalysts exhibited satisfying abilities to catalyze aquathermolysis at low temperatures (130–200 °C). Specifically, 25 % ZrO2−MoO3/MLSB catalyst displayed the optimal heavy oil viscosity reduction rate (86.1 %) at 200 °C, which was attributed to hydrophobicity, more active components and strong acid sites. The highest viscosity reduction rate of heavy oil was obtained with 25 % ZrO2−MoO3/MLSB at 200 °C and a catalyst content of 3 wt%. Continuing to increase the catalyst content decreased the viscosity reduction rate, likely due to catalyst agglomeration hindering the contact between the active component and heavy oil. Moreover, the viscosity reduction effect of the catalyst increased with higher reaction temperatures. Additionally, a reaction network of aquathermolysis catalyzed by ZrO2−MoO3/MLSB was proposed. These findings contribute to the development of efficient catalytic systems for aquathermolysis and provide insights into the application of biochar-based catalysts in heavy oil viscosity reduction.

Self-Assembled Aminated and TEMPO Cellulose Nanofibers (Am/TEMPO-CNF) Aerogel for Adsorptive Removal of Oxytetracycline and Chloramphenicol Antibiotics from Water.

Antibiotics are used for the well-being of human beings and other animals. Detectable levels of antibiotics can be found in pharmaceutical, municipal, and animal effluents. Therefore, the treatment of antibiotic contaminated water is of great concern. In this study, we fabricated a sustainable aminated/TEMPO cellulose nanofiber (Am/TEMPO-CNF) aerogel to remove oxytetracycline (OTC) and chloramphenicol (CAP) from synthetic wastewater. The prepared aerogel was characterized using different analytical techniques such as elemental analysis, FTIR, TGA, SEM-EDS, and N2 adsorption-desorption isotherms. The characterization techniques confirmed the presence and interaction of quaternary amine -[NR3]+ and -COOH groups on Am/TEMPO-CNF with OTC and CAP, which validates the successful modification of Am/TEMPO-CNF. The adsorption process of the pollutants was examined as a function of solution pH, concentrations, reaction time, and temperatures. The maximum adsorption capacity was 153.13 and 150.15 mg/g for OTC and CAP, respectively. The pseudo-second order (PSO-2) was well fitted to both OTC and CAP, confirming the removal is via chemisorption. Hydrogen bonding and electrostatic attraction have been postulated as key factors in facilitating OTC and CAP adsorption according to spectroscopic studies. Energetically, the adsorption was spontaneous and endothermic for both pollutants. In conclusion, the efficient removal rate and excellent reusability of Am/TEMPO-CNF indicate the strong potential of the adsorbent for antibiotics' removal.

Direct Synthesis of MOF-74 Materials on Carbon Fiber Electrodes for Structural Supercapacitors.

The use of fossil fuels has contributed significantly to environmental pollution and climate change. For this reason, the development of alternative energy storage devices is key to solving some of these problems. The development of lightweight structures can significantly reduce the devices' weight, thereby reducing energy consumption and emissions. Combining lightweight structures with alternative energy storage technologies can further improve efficiency and performance, leading to a cleaner and more sustainable system. In this work, for the first time, MOF-74 materials with different divalent metal ions have been synthesized directly on carbon fiber, one of the most widely used materials for the preparation of electrodes for supercapacitors with structural properties. Different techniques, such as nitrogen adsorption-desorption isotherms, cyclic voltammetry or galvanostatic charge-discharge, among others, were used to evaluate the influence of the metal cation on the electrochemical capacitance behavior of the modified electrodes. The Co-MOF-74 material was selected as the best modification of the carbon fibers for their use as electrodes for the fabrication of structural supercapacitors. The good electrochemical performance shown after the incorporation of MOF materials on carbon fibers provides a viable method for the development of carbon fiber electrodes, opening a great variety of alternatives.

Relation between hydrophilic/hydrophobic characteristics of sludge extracellular polymeric substances and sludge moisture-holding capacity in hot-pressing drying

Sludge poses a serious threat to the environmental health. Hot-pressing drying has been proven efficient in sludge treatment because of the reduced thermal contact resistance, rapid increase in sludge temperature, and high drying rate. Sludge extracellular polymeric substances (EPS) significantly influence moisture transfer. However, whether in hot-pressing or traditional thermal drying, the effect of EPS on sludge moisture-holding capacity is rarely reported. Thereby, this study investigated the relationship between hydrophilic/hydrophobic characteristics of EPS and sludge moisture-holding capacity at various drying time and mechanical compression using XAD resin fractionation. Thermodynamic analysis indicated that sludge moisture desorption isotherms, net isosteric heat of desorption, and differential entropy presented a downward trend with the increase in drying time and mechanical compression, suggesting reduced sludge moisture-holding capacity. EPS analysis showed that at the same drying time, applying 25 kPa mechanical compression increased sludge temperature by 16 % and protein content by 13.8 %. At the same sludge temperature, protein content rose by 7.3 % compared to the drying without mechanical compression. It was concluded that the fast rise in sludge temperature and the mechanical extrusion facilitated the destruction of sludge microbial flocs, accelerating the release of intracellular and EPS-bound moisture and contributing to the decrease in moisture-holding capacity. Besides, tryptophan protein-like substances were the major source of hydrophilic/hydrophobic organic matter, compared to polysaccharide and humic acid-like substances. The gradually reduced sludge moisture-holding capacity was divided into three stages. Below 67 °C, the moisture desorption was dominated by the release of intracellular moisture. Below 85 °C, the increase in protein and the enhanced exposure of hydrophobic functional groups in protein improved the hydrophobicity of EPS. Above 85 °C, protein consumption due to thermal decomposition and browning reaction facilitated the desorption of EPS-bound moisture. Hence, this study provided novel insights into the mechanism of sludge drying.

A green synthetic method for cobalt(II,III) oxide nanoparticles with high surface activity

Objectives. To develop a new green method for the synthesis of nanosized materials of cobalt(II,III) oxide, with improved surface activity, using environmentally friendly precursors and solvents.Methods. A green method was proposed, in order to isolate Co3O4 nanoparticles with high surface activity. Instead of the usual organic solvents, three different natural sugars, including glycogen, sucrose, and glucose were used for the first time as templates. Water as a green solvent was used in all the steps. The polymorphic composition of the synthesized samples was determined by means of X-ray phase analysis. The morphology of the obtained crystallites was studied from micrographs of the oxide phases. Image Pro Plus 6 software was used to measure the size of nanoparticles. The surface activity of the isolated samples was studied using the Brunauer–Emmett–Teller method and the Langmuir method. The Barret–Joyner–Halenda method was used to determine the diameter, volume, and distribution of pores.Results. The crystallite sizes of the samples are 23 nm, 36 nm, and 30 nm for glucose, glycogen, and sucrose templates, respectively. Adsorption–desorption isotherms for samples obtained from complexes of glucose and sucrose correspond to type IV, indicating a strong interaction between the adsorbent and the adsorbed sample. The isotherm for the sample isolated from the complex with glycogen is of a different type and most likely indicates that this sample is almost completely mesoporous. The pore radii are found in the interval 1.2–1.6 nm.Conclusions. A new green method for the synthesis of nanosized particles of Co(II,III) oxide using natural saccharides and deionized water was developed. The composition, morphology, structure, and surface activity of the samples obtained were studied. It was shown that due to the polymeric structure of their metal complexes and the ability to bind active carbon on the surface of nanoparticles, natural saccharides can be used as matrices in the synthesis of nanosized metal oxides with high surface activity.

Water desorption isotherms and thermodynamic properties of Ora-pro-nóbis (Pereskia aculeata Miller)

Desorption isotherms of ora-pro-nóbis leaves were determined at storage (5 °C, 10 °C, 20 °C, 30 °C, and 40 °C) and drying (40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) temperatures by the gravimetric static method using saturated saline solutions to obtain relative humidities ranging from 5.20% to 98.48%. The net isosteric heat of desorption and thermodynamic properties such as differential enthalpy, differential entropy, and Gibbs free energy were also estimated. The GAB model presented the best parameters of fitting and the lowest Akaike and Bayesian information criteria values. The desorption isotherm patterns presented a sigmoid shape and were categorized as BET Type II sigmoid shape. The monolayer moisture content was estimated in 0.06 kg of water/kg of dry matter using the GAB model, and it remained constant at all temperatures. The leaves presented an optimal water activity equal to 0.35 at storage temperatures. The net isosteric heat of desorption decreased with increasing Xeq, and differential entropy increased with rising equilibrium moisture content (Xeq > 0.07). The enthalpy-entropy compensation was evaluated, and the desorption process is revealed to be entropy-driven and non-spontaneous.

Mercury removal performance of sulfated MnCe catalyst prepared by tobacco waste combustion synthesis

MnOx-CeO2 is a promising catalyst for Hg0 removal from coal flue gas at ∼150 °C but exhibits insufficient catalytic activity. Even though sulfation enhances the catalytic activity of MnOx-CeO2, gas-phase sulfation leads to SO2 poisoning and catalyst deactivation. In this study, we developed a liquid-phase sulfation strategy involving the direct combustion of cigarette butts soaked in a solution of sulfate and metal precursors to directly synthesize sulfated MnCe catalyst (SMC). SMC was characterized via N2 adsorption–desorption isotherms, SEM-EDS, XRD, XPS, and Hg-TPD. Both the MnCe catalyst and SMC exhibited good Hg0 oxidation efficiencies (66.46 % and 88.76 %, respectively) at 150 °C. The enhanced performance of SMC was attributed to the generation of abundant chemically adsorbed oxygen species on the SMC surface during sulfation. Moreover, the synergistic effect between the Ce4+ and Mn4+ species contributed to the improved catalytic performance of SMC. This strategy not only provides a one-step synthesis of sulfated catalysts but also has potential applications in Hg0 removal from coal flue gas in coal-fired power plants.

Label-free and early detection of HER2 breast cancer biomarker based on UiO-66-NH2 modified gold chip (Au/UiO-66-NH2) using surface plasmon resonance technique

Breast cancer is one of the leading causes of cancer death for women worldwide. This cancer occurs when the breast cells grow abnormally and spread uncontrolled. Although there are several treatments, including chemotherapy, radiation, and surgery in a clinical setting to cure cancer, these treatments cannot provide a 100 % success rate in eliminating cancer, mainly due to the late diagnosis of the disease. Thus, early detection is the key to provide better breast cancer treatment and a higher chance for survival. Herein, simple and sensitive biosensor by combining the emerging multifunctional materials of metal-organic frameworks (MOFs) with a label-free surface plasmon resonance (SPR) instrument was developed. Two types of stable Zirconium (Zr)-based MOFs, namely Zr benzene dicarboxylic acid (Zr-BDC or UiO-66) and Zr 2-amino-benzene dicarboxylic acid (Zr-BDC-NH2 or UiO-66-NH2) were synthesized using the solvothermal method. X-ray diffractometer (XRD) and fourier transform infra red (FTIR) confirmed the formation of the prepared UiO-66 and UiO-66-NH2. The electron microscopy and nitrogen adsorption desorption isotherm characterization reveal that the MOFs have a cubic crystal structure with a high surface area of 672.4 m2/g for UiO-66 and 286.1 m2/g for UiO-66-NH2. The MOFs are then functionalized on the SPR gold (Au) chip surface to serve as a matrix of Human Epidermal Growth Factor Receptor 2(HER2) antibody receptors. Interestingly, the functionalized SPR biosensors could detect the HER2 protein target with high sensitivity in the ng/mL range and a remarkable detection limit, which is 0.457 ng/mL for UiO-66-NH2. This LOD value is significantly lower than clinical concentrations of HER2 proteins in human blood (∼15 ng/mL), which indicate that the biosensor can offer the capability of early detection test.

Insight into the reaction mechanism of photocatalytic production of solketal

In this work, the behavior of a commercial TiO2 (Evonik P25) and synthesized CeO2 and Bi2WO6 photocatalysts in the photoacetalization of glycerol with acetone to obtain solketal under simulated sunlight was studied. The solids were characterized by X-ray diffraction (XRD), N2 adsorption desorption isotherms, Raman spectroscopy and UV–Vis spectroscopy techniques. The influence of the oxygen content in the reaction atmosphere (1–40% O2) was analyzed. It was concluded that oxygen is essential for the reaction taking place, suggesting the participation of the superoxide radical as an intermediate in the transfer of electrons. To confirm this point, p-benzoquinone, a known superoxide radical scavenger, was used to evaluate the role of O2. However, two opposite effects were observed for p-benzoquinone depending on the amount added to the reaction medium. Thus, for small amounts of p-benzoquinone a negative effect on the yield of solketal was observed, in agreement to its superoxide radical scavenger character. On the contrary, at high concentrations, p-benzoquinone enhanced the solketal yield obtained in the process. A mechanism is proposed by which the semiquinone radical formed acts as an intermediate capable of facilitating the transfer of electrons in the process, thereby improving the overall process. The catalyst showing the lowest catalytic activity was CeO2, whereas Bi2WO6 had a higher reaction rate and activity than TiO2 (P25), with both reaching approximately 78% conversion under optimum conditions. These results are promising because the conversion achieved is comparable to that obtained by acid catalysis, using sunlight as energy source.

Interchangeable effect of polyols-based zeolite on the separation of CO2, CH4, and N2 gases

The adsorptive separation process for CO2/CH4 and CH4/N2 gas separation has commercial potential, in biogas, Coalbed Methane process etc. although it remains to strive due to the absence of effective adsorbents. Zeolite NaY was used in this study due to its uniform pore structures, surface properties, and potential gas separation adsorbent. Zeolite NaY was modified by polyether polyols (PEPO) to get an adsorbent for selective separation of CO2/CH4 and CH4/N2 gas mixtures. The PXRD, FT-IR, GPC, 1H NMR, TEM, and surface area analysis were used to characterize the PEPO and PEPO-modified zeolite. The single component equilibrium adsorption desorption isotherms with PEPO modified NaY zeolites and NaY zeolite for CO2, CH4 and N2 were measured at 298, 313, and 328 K and up to 5 bar pressure. The isotherm data of CO2, CH4 and N2 were fitted in Dual Site Langmuir equations, and adsorption selectivity of CO2/CH4 and CH4/N2 gas mixtures was predicted using Ideal Adsorbed Solution Theory (IAST) method for 90:10, 50:50 (vol/vol) CH4/N2 and 80:20, 50:50 (vol/vol) CO2/CH4 feed gas mixtures representing coal bed methane gas composition and pressure conditions. The high surface area and hydroxyl groups in PEPO-modified NaY enhanced selectivity for CO2/CH4 and CH4/N2 gas separation. The selectivity predicted by the IAST method were 106.12 and 95.34 for 0.5 % PEPO-NaY (80:20 v/v and 50:50 v/v) for CO2/CH4 and 3.95 and 3.52 for 2 % PEPO-NaY (90:10 v/v and 50:50 v/v) for CH4/N2 at 298 K up to 5 bar respectively.

Process modeling and simulation of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood drying

This study simulate the process modeling of drying characteristics of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood under the influence of various process variables such as drying time, drying temperature, and airflow velocity. GmW and MaW moisture desorption isotherms, kinetics, and thermodynamics were also studied. Five (5) thin-layer and desorption isotherm drying models were used to model the moisture ratio and water activity data from the process. According to the anatomical analysis, the GmW sample has an average lumen size of 147.44 m, indicating a high moisture content. The results showed that the Guggenheim, Anderson, and de Boer (GAB) model with the lowest sum of squared error value (0.046) demonstrated the best-fit to the experimental desorption data for GmW samples and the Henderson-P model for MaW samples, while the Demir et al. model emerged as the best kinetics model fit for describing the moisture desorption isotherm and thin-layer drying kinetics. GmW effective diffusivity (Deff) values ranged from 3.671 × 10−8 to 5.378 × 10−8 m2/s and MaW effective diffusivity (Deff) values ranged from 2.923 × 10−8 to 4.678 × 10−8 m2/s. GmW and MaW activation energies were 252.702 kJ/mol and 313.604 kJ/mol, respectively. The thermodynamic studies revealed that the heat and mass transfer coefficients varied linearly with temperature, as the change in enthalpy (ΔH) and change in entropy (ΔS) decreased while the Gibbs free energy (ΔG) increased. The results obtained from this study demonstrated that the proposed drying process modeling and simulation approach could be successfully applied to investigate the wood drying phenomena. The information can be used to reduce the drying costs and improve the wood quality.

Nectarine powder of Bulgarian origin: Physicochemical composition, antioxidant activity, microbiological and sorption characteristics

One way to improve the quality of food products is by conducting more thorough research on regional foods. This approach has several benefits, such as promoting human health, supporting the local economy, and preserving cultural food traditions. In this regard, our study investigated the potential of nectarine powder as a regional fruit product that could be developed into a global innovation. The present study examined: the physicochemical composition, antioxidant activity, microbiological load, and adsorption and desorption characteristics of the nectarine powder. The fruit powder was acquired through the use of a heat pump dryer, where drying took place at 42 °C for a duration of 8 h until achieving a moisture content ranging from 13.5 % to 14.5 %. The approximate physicochemical values are as follows: proteins, total carbohydrates, crude fiber, ash content and total lipids. Microbiological parameters, namely the total count of mesophilic aerobic and facultative anaerobic microorganisms, yeasts and molds, Escherichia coli, Salmonella spp., coagulase-positive staphylococci, and coliforms were checked and found to be within the acceptable limits as stipulated by the relevant state standards. Antioxidant activity was demonstrated through the utilization of various methods, including DPPH (33.19 ± 0.09mMTE/g extract), ABRS (2.55 ± 0.05mMTE/g extract), FRAP (1.43 ± 0.03mMTE/g extract) and CUPRAC (0.83 ± 0.01mMTE/g extract) methods. Investigation of the mass transfer sorption characteristics is performed using the gravimetric-static method. The conditions of the experiment were selected according to the usual conditions in which the food products are found in the commercial depot. The equilibrium and monolayer moisture data are investigated at 10 °C, 25 °C and 40 °C and relative air humidity in the wide range from 11 % to 87 %, achieved by the salts saturated solutions. To depict the adsorption and desorption isotherms, the modified models of Halsey, Chung-Pfost, Henderson, and Oswin were selected.

Use of murici (Byrsonima crassifolia) and jabuticaba (Plinia cauliflora) residues in the preparation of porous materials: Effect of pH on the adsorption efficiency of the contaminants phenol, diethylphthalate and amoxicillin

Activated charcoals with the chemical activator (H3PO4) were synthesized from agro-industrial residues, Murici seeds (CA-MU) and Jabuticaba (CA-JA). The synthesized charcoals were characterized by thermogravimetric analysis (TG), N2 adsorption and desorption isotherms, Fourier transform infrared spectroscopy (FTIR), point of zero charge (pHPZC) and scanning electron microscopy (SEM). The charcoals produced presented mesoporous characteristics, surface areas of 884.226 m2.g−1 for CA-JA and 556.97 m2.g−1 for CA-MU, mean pore diameters suitable for adsorption of phenol (PHE), diethylphthalate (DEP) and amoxicillin (AMX). The chemical characterization indicated the acid profile of the surface of the charcoals, which presented pHPZC of 6.3 (CA-JA) and 6.7 (CA-MU). The adsorption studies, in aqueous solution of the pollutants (PHE), (DEP) and (AMX), indicated that the removal capacity is strongly influenced by the pH of the solution. Toxicity tests demonstrated that the adsorption process was responsible for decreasing the toxicity of the pollutants studied. Thus, given the results presented, the activated charcoals synthesized can be considered high potential adsorbents for applications in the removal of organic pollutants in aqueous solutions.

Nitrogen-enriched flexible metal-organic framework for CO2 adsorption.

A novel MOF named [Zn2(L)(DMF)] was synthesized using solvothermal methods from the reaction of the new linker (4,4',4''-(4,4',4''-(benzene-1,3,5-triyltris(methylene))tris(3,5-dimethyl-1H-pyrazole-4,1-diyl))tribenzoic acid) and Zn(NO3)2·6H2O. This new MOF was characterized by means of different techniques: powder X-ray diffraction, N2 adsorption and desorption isotherms, thermogravimetric analysis, and scanning electron microscopy. Furthermore, suitable crystals were obtained, which allowed us to perform the X-Ray structure determination of this MOF. The capability of these new MOF to adsorb CO2 at different temperatures was measured and its isosteric enthalpy of adsorption was calculated. The novel MOF shows an uncommon node composed of a Zn3(-COO)6(DMF)2, and the asymmetric unit contains one crystallographically independent linker, one DMF molecule, and two Zn atoms. The [Zn2(L)(DMF)] MOF is a microporous material with high crystallinity and stability up to 250 °C. The multiple nitrogenated pyrazole linkers in its framework enhance its CO2 adsorption capabilities. This material exhibits a low CO2 isosteric enthalpy of adsorption (Hads), comparable to previously reported values for similar nitrogenated materials. All the observed CO2 adsorption capacities were further supported by DFT calculations.

Математическое моделирование взаимодействия водорода с многокомпонентными ИМС на основе гексагональных фаз Лавес

To calculate the properties of previously unstudied intermetallic compounds (IMC), a statistical model developed in our laboratory was applied, which uses already known literature data on the thermodynamic parameters of absorption / desorption reactions of hydrogen for intermetallic compositions with the structure of hexagonal Laves phases. For the alloys, hydrogen absorption and desorption isotherms were plotted. Comparison of calculated and experimental data was carried out to assess the correctness of the forecast model.

PHASE CONCENTRATION EQUILIBRIUM DURING DRYING COLLOID CAPILLARY-POROUS MATERIAL - PEA

In this work, we studied experimentally the phase concentration equilibrium during drying of a colloidal capillary-porous material - peas. The studies were carried out by a static (exsicator) method using saturated aqueous solutions of mineral salts, with the help of which certain relative air humidity was created in the desiccators. To establish equilibrium, the samples were kept in desiccators for one month. The values of relative air humidity over salt solutions at the corresponding temperatures were found from the well-known Schneider diagram. Moisture desorption isotherms were determined, for which high-moisture pea samples were placed in exsicators. The experiments were carried out at three temperatures: 30, 40 and 50 °C. According to the measurement data, moisture desorption isotherms were constructed in the coordinates "relative air humidity - equilibrium moisture content of the material." The resulting desorption isotherms were described by the Henderson equation, for which the values of the coefficients of this equation were found and their statistical evaluation was given. The data on the balance of peas were compared with similar data for other plant colloidal capillary-porous materials: vegetables (carrot and beet cuts), grain crops (rye, wheat and corn grains), and vegetable seeds. A significant influence of the type of culture on the equilibrium moisture content of the material during drying is shown, while the intraspecific influence on the equilibrium moisture content is less important. The obtained data on moisture desorption isotherms during drying can be used for engineering calculations of the kinetics of drying pea grain and for choosing the temperature and humidity conditions for its storage after drying.

Sorption and desorption isotherms of celery roots

An experimental study for determining the wet basis equilibrium moisture content in celery root (Apium graveolens) was conducted. Empirical equations describing the isotherms of sorption and desorption of the product at a temperature of 20°C were obtained. The values for the wet basis equilibrium moisture content for higher temperatures – 40, 60 and 80°C were theoretically calculated. All results were summarized in analytical, graphical and tabular form.

Surface Characterization Gel Grown Cerium Tartrate Crystals

Cerium tartrate crystals were grown from sodium metasilicate gel and water solutions of tartaric acid and cerium chloride as the reactants. Crystals grown were spherulitic in size. The principle objective of this investigation is to determine the surface area, pore volume and pore size of CeT sample. BET surface area was calculated from the BET plot; pore size distributions were calculated using BJH model. The pore volume was measured at the single point of p/p0 = 0.05. The Adsorption / Desorption Isotherm for cerium tartrate, Pore Size Distribution by BJH Method, Pore Size Distribution by DFT method and Volume Histogram By DFT Method was studied respectively for the CeT sample. The isotherm obtained for the sample demonstrates that it belongs to the type II isotherm.