Mesoporous SiO2 Particles Combined with Fe Oxide Nanoparticles as a Regenerative Methylene Blue Adsorbent

Mesoporous SiO2 adsorbents were combined with Fe oxide nanoparticles (similar to 10 nm) that can catalyze thermal oxidation of organic compounds at low temperatures. Fe oxide nanoparticle (similar to 10 nm)-incorporated SiO2 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/SiO2 particles were examined and compared to those of bare SiO2. Upon deposition of Fe oxide nanoparticles, not only the equilibrium adsorption capacity of mesoporous SiO2 for methylene blue (MB) was improved but also the reusability of SiO2 adsorbent was increased significantly. The adsorption ability of fresh Fe oxide/SiO2 particles can be almost fully recovered by simple thermal annealing at atmospheric conditions (400 degrees C), whereas that of bare SiO2 reduced significantly under same conditions. In addition, full recovery of initial MB adsorption ability of Fe oxide/SiO2 can be achieved by a 100 degrees 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/SiO2 adsorbent. In addition to reusability, the equilibrium adsorption capacity of mesoporous SiO2 particles for various cationic dye molecules, such as MB, malachite green, and rhodamine B, can be improved by combining Fe oxide nanoparticles.