Preparation and study of silica and APTES–silica-modified NiFe2O4 nanocomposites for removal of Cu2+ and Zn2+ ions from aqueous solutions

• Published in: Journal of sol-gel science and technology Vol. 91; no. 3; pp. 596 - 610
• Main Authors: Isasi, J., Arévalo, P., Martin, E., Martín-Hernández, F.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-09-2019; Springer Nature B.V
• Subjects: Absorption spectra; Adsorption; Aminopropyltriethoxysilane; Aqueous solutions; Banded structure; Ceramics; Chemistry and Materials Science; Coating; colloids; Composites; Copper; etc.; fibers; Fourier transforms; Glass; Infrared analysis; Infrared spectroscopy; Inorganic Chemistry; Magnetic cores; Materials Science; Nanocomposites; Nanoparticles; Nanotechnology; Natural Materials; Nickel ferrites; Optical and Electronic Materials; Original Paper: Nano-structured materials (particles; Reaction time; Silicon dioxide; Spectrum analysis; Spinel; Synthesis; Tetraethyl orthosilicate; Thickness; Titration; Transmission electron microscopy; X-ray diffraction; Nanocomposite; Magnetic materials; Hydrothermal synthesis; Adsorption; Pollutant removal
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-019-05067-3

Silica and (3-aminopropyl)triethoxysilane (APTES)–silica-modified NiFe
2
O
4
samples were successfully synthesized by a two-/three-step process, depending on the sample, including the preparation of nickel ferrite sample by hydrothermal synthesis, the coating of its surface with silica, and the subsequent functionalization with APTES. Samples were characterized by X-ray diffraction (XRD), Fourier transform-infrared (FTIR) analysis, transmission electron microscopy, and
M
–
H
curves. XRD data of the NiFe
2
O
4
sample shows diffraction maxima that can be indexed in a cubic symmetry of space group
Fd
-3
m
with
Z
 = 8, compatible with an inverse spinel-type structure. The estimated average crystalline size is 22 nm. All FTIR spectra show absorption bands between 600 and 400 cm
−1
, characteristic of spinel-type structure. Bands attributed to the vibration of O–Si–O and Si–O–Si bonds are found in the spectra of the silica-coated samples. APTES–silica-modified NiFe
2
O
4
nanocomposites show an increase in coating thickness as the reaction time with tetraethoxysilane increases. A practically superparamagnetic behavior was found for the synthesized NiFe
2
O
4
sample with a magnetization of 47 emu/g. This value is slightly reduced with the thickness of the nonmagnetic coating. The ultraviolet–visible spectroscopy measurements and titration curves clearly demonstrated that the APTES–silica-modified NiFe
2
O
4
nanocomposites could be efficient materials for the removal of Cu
2+
and Zn
2+
ions from aqueous solutions. The best adsorption is found in the NiFe
2
O
4
@SiO
2
(3)–APTES(6) sample, while the NiFe
2
O
4
@SiO
2
(6)–APTES(12) sample seems to be the most suitable for its application, considering its better adsorption capacity and its easy separation from the aqueous solution in the presence of an external magnetic field.
Highlights
Amino-functionalized NiFe
2
O
4
@SiO
2
core-shell nanocomposites are prepared.
Magnetic cores are obtained by a urea-mediated hydrothermal synthesis.
TEM confirms the formation of a uniform coating around magnetic nanoparticles.
Cu
2+
and Zn
2+
adsorption evidence the reaction of the cations with amino groups.
Nanocomposites reach an adsorption capacity higher than 10% of their own weight.