Abstract
Chitosan-coated magnetic nanoparticles (CMNP) were prepared in one-step by precipitation in a high-aqueous phase content reverse microemulsion in the presence of chitosan. The high-aqueous phase concentration led to productivities close to 0.49 g CMNP/100 g microemulsion; much higher than those characteristic of precipitation in reverse microemulsions for preparing magnetic nanoparticles. The obtained nanoparticles present a narrow particle size distribution with an average diameter of 4.5 nm; appearing to be formed of a single crystallite; furthermore they present superparamagnetism and high magnetization values; close to 49 emu/g. Characterization of CMNP suggests that chitosan is present as a non-homogeneous very thin layer; which explains the slight reduction in the magnetization value of CMNP in comparison with that of uncoated magnetic nanoparticles. The prepared nanoparticles show high heavy ion removal capability; as demonstrated by their use in the treatment of Pb2+ aqueous solutions; from which lead ions were completely removed within 10 min.
Highlights
Magnetic nanoparticles (MNP) constitute a very interesting material due to their wide range of applications in the technological [1] and biomedical fields [2]
In our last work on the one-step preparation of coated magnetic nanoparticles (CMNP), we reported the use of a reverse microemulsion composed of 0.25 M aqueous solution of a FeCl3·6H2O/FeCl2·4H2O mixture (3/2, mol/mol) containing
The results above allowed to calculate 66.9 and 62.5 mg chitosan covering each gram of magnetic material, for MHQ80 and MHQ80-R, respectively, which are higher than the theoretical value (≈53.0 mg/g) assuming 100% conversion to magnetite in the precipitation reaction and all chitosan used in the recipe covering the nanoparticles. This apparent contradiction could arise from conversions slightly lower than 100% in the precipitation reactions along the formation of a mixture of magnetite and maghemite instead of only magnetite. These results indicate that the known mechanism in the preparing of magnetic nanoparticles in reverse microemulsions is not modified by the presence of chitosan
Summary
Magnetic nanoparticles (MNP) constitute a very interesting material due to their wide range of applications in the technological [1] and biomedical fields [2]. The very small size (≈10 nm in average diameter) endows them with superparamagnetic character; in addition, the CMNPs showed a relatively high final magnetization value of 65.6 emu/g at room temperature and 20 kOe. More recently, our group reported the use of reverse microemulsions as templates for obtaining. In our last work on the one-step preparation of CMNP, we reported the use of a reverse microemulsion composed of 0.25 M aqueous solution of a FeCl3·6H2O/FeCl2·4H2O mixture (3/2, mol/mol) containing. In we report a one-step CMNP preparation in a reverse microemulsion with much higher aqueous phase content (26 wt%), which notably increases the process productivity of nanoparticles covered with a very thin chitosan layer
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