Summary: | Iron (III) oxide (Fe<sub>3</sub>O<sub>4</sub>) and sodium dodecyl sulfate (SDS) coated iron (III) oxide (SDS@Fe<sub>3</sub>O<sub>4</sub>) 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 (H<sub>2</sub>O<sub>2</sub>) was carried out and the influence of Fe<sub>3</sub>O<sub>4</sub> and SDS@Fe<sub>3</sub>O<sub>4 </sub>magnetic NPs on the degradation rate was assessed. The activity of magnetic NPs, viz. Fe<sub>3</sub>O<sub>4</sub> and SDS@Fe<sub>3</sub>O<sub>4</sub>, 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 H<sub>2</sub>O<sub>2</sub> concentration and within 5.0 × 10<sup>−2</sup> to 4.0 × 10<sup>−1</sup> M H<sub>2</sub>O<sub>2</sub>, the observed pseudo-first-order kinetic rates (k<sub>obs</sub>, s<sup>−1</sup>) for the degradation of RB (10 mg L<sup>−1</sup>) at pH 3 and temperature 25 ± 2 °C were between 0.4 and 1.7 × 10<sup>4</sup> s<sup>−1</sup>, while in presence of 0.1% <i>w</i>/<i>v</i> Fe<sub>3</sub>O<sub>4</sub> or SDS@Fe<sub>3</sub>O<sub>4</sub> NPs, k<sub>obs</sub> were between 1.3 and 2.8 × 10<sup>4</sup> s<sup>−1</sup> and between 2.6 and 4.8 × 10<sup>4</sup> s<sup>−1</sup>, respectively. Furthermore, in presence of Fe<sub>3</sub>O<sub>4 </sub>or SDS@Fe<sub>3</sub>O<sub>4</sub>, k<sub>obs</sub> increased with NPs dosage and showed a peaked pH behavior with a maximum at pH 3. The magnitude of thermodynamic parameters E<sub>a</sub> and ΔH for RB degradation in presence of SDS@Fe<sub>3</sub>O<sub>4</sub> were 15.63 kJ mol<sup>−1</sup> and 13.01 kJ mol<sup>−1</sup>, respectively, lowest among the used catalysts, confirming its effectiveness during degradation. Furthermore, SDS in the presence of Fe<sub>3</sub>O<sub>4</sub> NPs and H<sub>2</sub>O<sub>2</sub> remarkably enhanced the rate of RB degradation.
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