Anna Strzelewicz

Preparation and Characterization of Iron Oxides – Polymer Composite Membranes

Composite membranes of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or ethyl cellulose filled with magnetic nanoparticles, that is, ferroferric oxides (Fe3O4) were prepared. These membranes were examined for nitrogen and oxygen permeability. In the case of ethylcellulose membranes the gas flow was too high, since the macropore were formed. In further permeation measurements PPO membranes with 1 to 10 w/w% magnetic particles content were investigated. For the higher concentration of magnetite (more than 20%) in PPO polymer solution sedimentation phenomenon was observed. Mass transport coefficients (permeation and selectivity) were evaluated. Selectivity of the investigated membranes changed with the weight fraction of magnetic particles from oxygen (plain) towards nitrogen (2 and more w/w%).

Magnetic mixed matrix membranes in air separation

Ethylcellulose (EC) or linear polyimide (LPI) and magnetic neodymium powder particles MQP-14-12 were used for the preparation of inorganic-organic hybrid membranes. For all the membranes, N2, O2 and air permeability were examined. Mass transport coefficients were determined using the Time Lag System based on dynamic experiments in a constant pressure system. The results showed that the membrane permeation properties were improved by the addition of magnetic neodymium particles to the polymer matrix. The magnetic ethylcellulose and polyimide membranes exhibited higher gas permeability and diffusivity, while their permeability selectivity and solubility were either unchanged or slightly increased. Polyimide mixed matrix membranes were characterised by a higher thermal and mechanical stability, larger filler loading, better magnetic properties and reasonable selectivity in the air separation.

Influence of Various Parameters on the Air Separation Process by Magnetic Membranes

Polymer membranes filled with magnetic powder and magnetized, used for an air enrichment, are investigated. Various polymer matrix with different types and granulation of dispersed magnetic powder were used for the preparation of the membranes. All membranes were examined for N2, O2, and air permeability. Mass transport coefficients were evaluated basing on Time Lag methods and D1-D8 system. Structure and morphology of the obtained membranes were investigated using fractal analysis. Box counting method for calculating generalized fractal dimension was applied. Obtained results allowed to optimize the preparation procedure of magnetic membranes with the best permeation properties.

Magnetic Mixed Matrix Membranes Consisting of PPO Matrix and Magnetic Filler in Gas Separation

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and magnetic neodymium powder particles MQP-14-12 have been used for the preparation of magnetic mixed matrix membranes. Permeability diffusion and sorption coefficients of O2, N2, and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on dynamic experiments in a constant pressure system. The influence of magnetic field and magnetic powder particles on the gas transport properties of MMMs was studied. The results showed that the membrane permeation properties were improved with the magnetic neodymium particle filling. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes showed higher gas permeability, while their permselectivity and solubility were rather maintained or slightly increased. The results also showed that the magnetic powder addition enhanced gas diffusivity significantly in EC and PPO membranes.

The Study of Ethanol/Water Vapors Permeation through Sulfuric Acid Cross-Linked Chitosan Magnetic Membranes

Sulfuric acid cross-linked chitosan membranes filled with a different amount of magnetite, were prepared. The permeation behavior of ethanol and water vapors in vapor permeation experiments were studied. Permeation rates were measured. Mass transport coefficients were evaluated. The study has been carried out to determine the influence of magnetic powder dispersed inside of the chitosan membrane on ethanol-water separation. The diffusion, fluxes, and permeation coefficients increased with greater amount of magnetite content. The separation factor increased with increasing flux and the best results were achieved for the membrane containing 15% w/w magnetite. The research allows optimizing the preparation procedure of chitosan magnetic membranes cross-linked by sulfuric acid with the best permeation properties.

A spectrophotometric method for plant pigments determination and herbs classification

Twenty herbs, showing medicinal benefits on human life, like Taraxacum officinale, Plantago lanceolata, Hypericum perforatum, Ocimum basilicum, Melissa officinalis, Mentha piperita, and others, were tested. The percentage content of pigments, i.e. chlorophylls, carotenoids, and flavonoids, in the chosen herbs was determined. The spectrophotometric method, which is quick and readily available, was used. Measurements required pigment extraction with a solvent. Ethanol was used for the determination of chlorophylls and carotenoids, and acetone for the determination of flavonoids. Hierarchical agglomerative cluster analysis was performed in order to confirm the experimental results. The study of flavonoids content showed an interesting regularity which can be used for the classification of herbs. Plants belonging to the Lamiaceae family showed the flavonoids content in the range from 0.18 % to 0.68 %, whereas those belonging to the Apiaceaehas family showed the flavonoids content in the 0.75–1.20 % range.

Permeation of ethanol and water vapors through chitosan membranes with ferroferric oxide particles cross-linked by glutaraldehyde and sulfuric(VI) acid

ABSTRACT Chitosan membranes filled with different amount of ferroferric oxides and cross-linked by two different agents, i.e. sulfuric acid or glutaraldehyde, were prepared and the influence of iron oxide and cross-linking agents on ethanol and water permeation has been discussed. Ethanol and water vapors permeation rates were determined using the measuring cell method and mass transport coefficients were evaluated. It was found that permeation of water for both types of chitosan membranes after addition of magnetite gradually increased. Furthermore, the difference between ethanol/water permeation coefficients was larger for glutaraldehyde cross-linked membranes (CHGA) than for sulfuric acid cross-linked membranes (CHSA).

The influence of metal oxides on the separation properties of hybrid alginate membranes

ABSTRACT Alginate membranes filled with different metal oxide particles were prepared and the influence of the presence of different amounts of Fe3O4, ZnO, and Ag2O particles on ethanol and water permeation was discussed. Ethanol and water vapour permeation rates were determined using the measuring cell method, and the mass transport coefficients were evaluated. It was found that the highest transport parameters were obtained for membranes with the highest metal oxide content. Furthermore, the highest flux, equal 8.49 kg·m−2·h−1, was obtained for the alginate membrane filled with 15 wt% of silver oxide particles, while the greatest selectivity coefficients were noted for membranes containing magnetite. In this case, for the alginate membrane with 15 wt% of magnetite content, the selectivity coefficient reached the best value of 108.15.

Structure-diffusion relationship of polymer membranes with different texture

Two-dimensional diffusion in heterogenic composite membranes, i.e., materials comprising polymer with dispersed inorganic fillers, composed of ethylcellulose and magnetic powder is studied. In the experimental part, the morphology of membranes is described by the following characteristics: the amount of polymer matrix, the fractal dimension of polymer matrix, the average size of polymer matrix domains, the average number of obstacles in the proximity of each polymer matrix pixel. The simulation work concentrates on the motion of a particle in the membrane environment. The focus is set on the relationship between membranes morphology characterized by polymer matrix density, its fractal dimension, the average size of domains, and the average number of near obstacles and the characteristics of diffusive transport in them. The comparison of diffusion driven by Gaussian random walk and Lévy flights shows that the effective diffusion exponent at long time limits is subdiffusive and it does not depend on the details of the underlying random process causing diffusion. The analysis of the parameters describing the membrane structure shows that the most important factor for the diffusion character is the average size of a domain penetrated by diffusing particles. The presented results may be used in the design and preparation of membrane structures with specific diffusion properties.