Photocatalytic Degradation of Organic Dyes by Magnetite Nanoparticles Prepared by Co-Precipitation.

Iron oxide nanoparticles were synthesized by co-precipitation using three different iron salt stoichiometric mole ratios. Powder X-ray diffraction patterns revealed the inverse cubic spinel structure of magnetite iron oxide. Transmission electron microscopic images showed FeO nanoparticles with different shapes and average particle sizes of 5.48 nm for FeO-, 6.02 nm for FeO-, and 6.98 nm for FeO- with an energy bandgap of 3.27 to 3.53 eV. The as-prepared FeO nanoparticles were used as photocatalysts to degrade brilliant green (BG), rhodamine B (RhB), indigo carmine (IC), and methyl red (MR) under visible light irradiation. The photocatalytic degradation efficiency of 80.4% was obtained from FeO- for brilliant green, 61.5% from FeO- for rhodamine B, and 77.9% and 73.9% from FeO- for both indigo carmine and methyl red. This indicates that FeO- is more efficient in the degradation of more than one dye. This study shows that brilliant green degrades most effectively at pH 9, rhodamine B degrades best at pH 6.5, and indigo carmine and methyl red degrade most efficiently at pH 3. Recyclability experiments showed that the FeO photocatalysts can be recycled four times and are photostable.