In the present work is reported, following a facile process, the synthesis of cobalt ferrite nanoparticles covered with a shell of SiO2, and then, covered with a shell of TiO2. In the first step, cobalt ferrite nanoparticles were prepared by coprecipitation of Co+2 and Fe +2 ions in basic medium, followed by a simple controlled oxidation process carried out by nitrate ions in basic medium with inert atmosphere at 95°C for 24h. In the second step, SiO2 particles were deposited by heterogeneous nucleation onto the surface of the ferrite in alcohol medium by alkalinization of tetraethylortosilane solutions, finally, in the third step, the TiO2 shell film is deposited by using sol-gel technique. Characterization techniques were performed to determine the particle morphology and size distribution (Scanning electron microscopy), crystalline structure (X-ray diffraction). Results showed that cobalt ferrite nanoparticles can be obtained following this synthesis route without using surfactants as size drivers, which is a common reagent in nanoparticle preparation, giving a size distribution of 162 ± 30 nm and a polyhedral geometry. Also, it was observed that SiO2 is homogeneously distributed onto the surface of the cobalt ferrite, and that TiO2 shell films covered well, creating a catalyst that also presents magnetic response. This kind of catalyst nanomaterial, presents a magnetic response, and is a stable and environmentally safe, then could be separated easily from the aqueous medium at the end of the purification process by applying an external magnetic field.
In the present work, photocatalytic oxidation of Rhodamine B solutions were performed using a composite material prepared by titanium dioxide films deposited onto cobalt ferrite nanoparticles. Cobalt ferrite nanoparticles were prepared by coprecipitation of Co(II) and Fe(II) ions in basic medium, followed by a controlled oxidation process carried out by nitrate ions in basic medium in inert atmosphere at 95°C. The effect of 2 alcohols (ethanol and 2-propanol) as solvents in the deposition of TiO2 films was studied as a function of CoFe2O4/TiO2 mass ratios. Cobalt ferrite nanoparticles exhibited (36 ± 20) nm diameter with spheroidal shapes as confirmed by SEM studies. TiO2 films deposited onto CoFe2O4 were thicker using ethanol as solvent according to SEM and TEM studies. Cobalt ferrite nanoparticles exhibit a weak oxidation behaviour since around 40% of Rhodamine is eliminated after 90 min of exposition. The 4 composite materials studied oxidize 100% of Rhodamine B after 60 min of reaction and kinetics results fitted a second order degradation reaction equation. As Rhodamine B solution pH was 5.83, faster reactions occur when composite materials develop low surface charge (PZC closer to 5.83) due to small surface charge repulsion. Materials prepared with CoFe2O4/TiO2 ratios between 4 to 6 present higher kinetic constants which is confirmed by a faster Rhodamine B degradation
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.