Mesoporous SiO Particles Combined with Fe Oxide Nanoparticles as a Regenerative Methylene Blue Adsorbent.

Mesoporous SiO adsorbents were combined with Fe oxide nanoparticles (∼10 nm) that can catalyze thermal oxidation of organic compounds at low temperatures. Fe oxide nanoparticle (∼10 nm)-incorporated SiO adsorbents were prepared via a temperature-regulated chemical vapor deposition method followed by a thermal annealing process. The removal efficiency and reusability of Fe oxide/SiO particles were examined and compared to those of bare SiO. Upon deposition of Fe oxide nanoparticles, not only the equilibrium adsorption capacity of mesoporous SiO for methylene blue (MB) was improved but also the reusability of SiO adsorbent was increased significantly. The adsorption ability of fresh Fe oxide/SiO particles can be almost fully recovered by simple thermal annealing at atmospheric conditions (400 °C), whereas that of bare SiO reduced significantly under same conditions. In addition, full recovery of initial MB adsorption ability of Fe oxide/SiO can be achieved by a 100 °C annealing process. Fourier transform infrared, thermogravimetric analysis, and X-ray photoelectron spectroscopy analyses indicated that Fe oxide nanoparticles catalyzed thermal degradation of adsorbed MB molecules, resulting in the improved reusability of the Fe oxide/SiO adsorbent. In addition to reusability, the equilibrium adsorption capacity of mesoporous SiO particles for various cationic dye molecules, such as MB, malachite green, and rhodamine B, can be improved by combining Fe oxide nanoparticles.