Search

Nanoscale magnetite (Fe3O4) and nanocomposite based on it (Fe3O4/SiO2) were synthesized. In solutions of different ionic strength (0.015 and 0.15 M NaCl) by pH-metry, the acid–base properties of the surface were studied: the pH value of the isoin state of the surface (рHIIP), the total concentration, and values of Ki and pK of surface hydroxyl groups active in the pH range 4–9 and are calculated dependencies of the particles of hydroxyl groups of the surface on the pH of the medium. It was found that neutral hydroxyl groups are predominant for the synthesized sample magnetically sensitive nanoparticles (MNPs), which make it possible to form centers of both acidic and base types. Thus, for Fe3O4 to pH = 6 active base centers (C=155.56⋅10−5 − 141.59⋅10−5 mol⋅g−1), the strength of which decreases with decreasing pH (pK = 2.65 ± 0.01–4.48 ± 0.01 (2.59 ± 0.003 − 4.70 ± 0.008 for 0.15 M NaCl solution). Acid centers in a very small amount (4.93⋅10−6 − 2.68⋅10−6 mol⋅g−1) are fixed in the pH range 7–9 and show weakly acidic properties (pK = 10.95 ± 0.21 − 11.31 ± 0.18 (11.34 ± 0.04 − 11.94 ± 0.17 for 0.15 M NaCl solution). For the Fe3O4/SiO2 surface, neutral centers are predominant, which are characterized by the detection of acidic properties, which makes it possible to form acid-type centers, the concentration of which is higher in 0.15 M NaCl solution (C = 237.58⋅10−5 mol⋅g−1), (C for 0.015 M NaCl solution = 150.54⋅10−5 mol⋅g−1), whose strength decreases with increasing pH (pK2=4.69 ± 0.03 − 8.6 ± 0.08 (4.91 ± 0.1 − 9.32 ± 0.09 for 0.15 M NaCl solution)). [ABSTRACT FROM AUTHOR]

The method for chitosan (CS) covalent immobilization onto NH2-functionalized magnetite nanoparticles surface is presented. Covalent binding of CS to the magnetite surface proceeds using a free -CH2OH group of CS and a NH2-group of magnetite with epichlorohydrin (ECH) as a cross-linker. The obtained nanocomposites were functionalized by diethylenetriaminepentaacetic acid (DTPA)-groups. Composites were characterized by elemental analysis, FTIR, XPS and ASAP methods. The total content of organic phase (CS-DTPA) in the hybrid material, appreciated by thermogravimetric analysis (TGA), was 3.7%. Considering the atomic ratio between oxygen in CS and oxygen in ECH residue, the chemical structure of the hybrid material is proposed. The adsorption of Gd-DTPA and Gd3+on the obtained nanocomposite was studied. The Freundlich isotherm fits all the experimental data better than the Langmuir adsorption. [ABSTRACT FROM AUTHOR]