Kinetic Studies on the Catalytic Degradation of Rhodamine B by Hydrogen Peroxide: Effect of Surfactant Coated and Non-Coated Iron (III) Oxide Nanoparticles.

Iron (III) oxide (Fe3O4) and sodium dodecyl sulfate (SDS) coated iron (III) oxide (SDS@Fe3O4) nanoparticles (NPs) were synthesized by the co-precipitation method for application in the catalytic degradation of Rhodamine B (RB) dye. The synthesized NPs were characterized using X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infra-red (FT-IR) spectroscopy techniques and tested in the removal of RB. A kinetic study on RB degradation by hydrogen peroxide (H2O2) was carried out and the influence of Fe3O4 and SDS@Fe3O4 magnetic NPs on the degradation rate was assessed. The activity of magnetic NPs, viz. Fe3O4 and SDS@Fe3O4, in the degradation of RB was spectrophotometrically studied and found effective in the removal of RB dye from water. The rate of RB degradation was found linearly dependent upon H2O2 concentration and within 5.0 × 10-2 to 4.0 × 10-1 M H2O2, the observed pseudo-first-order kinetic rates (kobs, s-1) for the degradation of RB (10 mg L-1) at pH 3 and temperature 25 ± 2 °C were between 0.4 and 1.7 × 104 s-1, while in presence of 0.1% w/v Fe3O4 or SDS@Fe3O4 NPs, kobs were between 1.3 and 2.8 × 104 s-1 and between 2.6 and 4.8 × 104 s-1, respectively. Furthermore, in presence of Fe3O4 or SDS@Fe3O4, kobs increased with NPs dosage and showed a peaked pH behavior with a maximum at pH 3. The magnitude of thermodynamic parameters Ea and ΔH for RB degradation in presence of SDS@Fe3O4 were 15.63 kJ mol-1 and 13.01 kJ mol-1, respectively, lowest among the used catalysts, confirming its effectiveness during degradation. Furthermore, SDS in the presence of Fe3O4 NPs and H2O2 remarkably enhanced the rate of RB degradation.