WITH POLYVINYLPYRROLI DONE

Field: Chemistry (Physical Sciences)

Data for the adsorption of medicinal preparations by ferromagnetic material particles in various media are important for solving medical problems. Modification of the surface of very fine ferromagnetic materials makes it possible to create a different order of composite materials which are of interest for practical medicine [1-4]. This work is devoted to studying the adsorption of very fine iron particles of polyvinylpyrrolidone (PVP), which as is well known [5], exhibits good adsorption properties towards different surfaces, it is not toxic, and it is soluble in organic solvents and water. Very fine iron powder with ellipsoidal and dendrite-shaped particles [6, 7] was studied. According to electron microscope data the average size of the ellipsoidal shape is 0.1-0.3 /zm and for the dendrite shape it is 0.5-0.7 /~m; their specific surface is 23.5 and 29.2 m2/g, respectively. The surface of very fine iron with an ellipsoidal particle shape is hydrophilic, but with a dendrite shape it is hydrophobic. Phases of ultra-small particles of iron oxides, Fe 2+, Fe 3+, and iron carbide are detected by NGR-spectroscopy on the surface of ellipsoidal shaped iron particles; on the surface of dendrkeshaped particles there are iron oxides and oleates. X-ray studies showed that they differ in the magnitude of mosaic blocks which for particles of ellipsoidal shape are 80 nm, and for the dendritic shape they are 200 nm. The difference in the structure of iron particles also specifies different surface properties connected with the presence of adsorption centers of a different nature, i.e., atoms of oxygen, hydrogen, hydroxyl groups, and aggregates of molecules with the general formula (H20)x [8]. Modification of the iron surface was performed with a static method by adsorbing PVP of the surface of particles [9]. The change in PVP content was evaluated from the difference in the original and equilibrium concentration of the alcoholic PVP solution related to a unit weight of adsorbent after separating the phases by centrifuging. The equilibrium concentration was estimated by a spectrophotometric method. The time for establishing equilibrium was determined by experiment (about 3 h). The adsorption isotherms from alcoholic solutions presented in Fig. 1 confirm this. Isotherm 1 for adsorption of PVP on iron with an ellipsoidal particle shape corresponds to the Langmuir type and it is characterized by approximately uniform adsorption to some limiting level, probably a filled monolayer. The hydrophilic surface of iron strengthens the interaction of PVP with the solvent. Presence of hydroxyl group molecules of the solvent on the surface of iron may be assumed to promote flat fastening of the PVP molecules. The structural formula of PVP provides a basis for assuming that formation of a hydrogen bond of the polymer with the particles surface by the type C = O is possible [5]. Presence at the surface of very fine iron particles of Fe 2+ and Fe 3+ ions, and the peptide.group of the PVP molecule also makes it possible for the cationactive properties of the polymer to develop. Isotherm 2 describes the adsorption of PVP on iron particles of dendrkic shape previously modified with a solution of oleic acid (0.05 mole/liter) during their preparation. As can be seen, the first stage of adsorption increases rapidly as a result of the fact that the surface of particles covered with a polymerophilic layer of oleic acid is actively impregnated by