TiO₂ films on CoFe₂O₄ nanoparticles for the photocatalytic oxidation of rhodamine B: Influence of the alcoholic solutions

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.