Papers by Keyword: Sorption Isotherms

Abstract: The object of this study was bentonite clay from the Ilnytskyi deposit in the Transcarpathian region. The clay was enriched in montmorillonite by sedimentation to remove the coarse-dispersed phase. Complex thermal, X-ray diffractometric, and energy-dispersive spectral analyses showed that the enriched bentonite consists mainly of Ca, Mg-montmorillonite. The sorption of methylene blue dye by the enriched bentonite was found to occur through an ion-exchange mechanism. Modeling of the experimental sorption isotherm data using the Langmuir equation revealed the influence of medium pH on the sorption characteristics of bentonite. The spent sorbent is recommended for application in sorption technologies for landfill reclamation and land restoration.

Abstract: Aromatic and medicinal plants are a natural source of pharmaceutical compounds with curative and therapeutic properties. They have been used for centuries to treat various ailments and offer alternative options to conventional treatments. Among these plants, Marrubium vulgare L., which is widely used in traditional medicine for diabetes treatment, has antioxidant potential as well as anti-inflammatory, healing, and soothing properties, attracting increasing medical interest. In this context, the hygroscopic behavior of Marrubium vulgare L. is reported. The adsorption-desorption isotherms of Marrubium vulgare leaves were determined using the standard static gravimetric method at three temperatures (30, 40, and 50 °C) to ensure physicochemical and microbiological stability throughout the storage process. The results showed that the adsorption-desorption isotherms of all samples followed a sigmoidal pattern, consistent with other agricultural products discussed in the literature. The optimal moisture content for conservation was also determined. The GAB (Guggenheim-Anderson-de Boer) and double polynomial models were the most suitable for describing the sorption curves. The adsorption-desorption data were examined to determine the moisture content of the monolayer (3.4-9.7%), properties of sorbed water in porous structures and surfaces, total heat of wetting, net isosteric heat of sorption, spreading pressure, differential entropy, and enthalpy-entropy compensation. It was also observed that the spreading pressure and average pore radius increase with rising relative humidity and temperature, leading to the appearance of defects on the surface of Marrubium vulgare leaves. Compensation theory is essential to consider when evaluating the impact of temperature on the adsorption-desorption properties. The Gibbs free energy was positive for sorption, indicating that the process is non-spontaneous.

Abstract: We have obtained magnetite nanoparticles (MNP) by using chemical coprecipitation of Fe²⁺ and Fe³⁺ in water solution. The size of these particles was less than 9 nm, and they possessed corresponding physical and chemical properties. Citric acid was used to stabilize magnetite particles suspension. The acid was affixed to the surface of the particles by adding it in fresh MNP solution during synthesis. Affixing carboxyl groups on the surface of MNP not only does improve particles' dispersion in solvent, but also allows adding further modifications to their surface. The properties of the particles' microstructure and morphology were determined with X-Ray diffraction (XRD) and transmission electron microscopy (TEM), whereas their magnetic properties were determined by means of automated pulse magnetic field analysis equipment. Magnetic measurements have shown that saturation magnetization was 94 emu/g with nanoparticles being at room temperature. We have also researched possible application of these particles as drug carriers by determining doxorubicin sorption capacity on the surface of MNPs. These MNPs have proven to have perspective ability to be a magnetic field-controlled carrier for cancer-treating drugs. The obtained particles can also potentially be used as a contrast medium for MRI.

Abstract: Method of electric-spark dispersion of iron particles in water, ethyl alcohol, phosphoric acid solution and hexane has been applied to produce composite magnetic nanosized powders. Their phase composition, dispersity, magnetic susceptibility, and adsorption-desorption properties towards anti-tumor remedy doxorubicin have been studied. It is shown that the obtained powder in hexane has the highest adsorption capacity towards doxorubicin. This is probably the evidence of surface compound formation. It is durable adsorption complex, which is formed from carbonyl and amine groups of organic cations and vacant orbitals of iron d-sublevel. The powder, obtained in hexane, can be dissolved in human blood plasma and amino acid solutions: possible time of iron elimination from human organism is smaller than 10 days. It is shown possibility of application iron-carbon sorbent is in quality of magnetic carrier doxorubicin to cancer cells.

Abstract: In the drying of porous media, the mass transport occurs in the pores as well as on the surface of the solid. The mechanisms involved can take place simultaneously, influenced by the predominant one and can change depending on the moisture content. In this work, the moisture effective diffusivity was estimated in solids with distinct structural properties in order to verify the predominant mechanisms according to the moisture content, analyzing the influence of the physical properties. The materials studied were NaY Zeolite, Kaolin, Silica and Alumina. The results of diffusion coefficient present a minimum at low moisture content that can be related to pore size.