Key Concepts on Transforming Magnetic Photocatalyst to Magnetic Dye-Adsorbent Catalyst
The magnetic dye adsorbent catalyst has been synthesized via hydrothermal processing of the magnetic photocatalyst followed by typical washing and thermal treatments. The magnetic dye adsorbent catalyst consists of a core-shell nanocomposite with the core of a magnetic ceramic particle (such as mixed cobalt ferrite (CoFe2O4), hematite (Fe2O3), and pure cobalt ferrite (CoFe2O4)) and the shell of nanotubes of dye adsorbing material (such as hydrogen titanate). The samples have been characterized for determining the phase structure, morphology, size, and magnetic properties using the Xray and selected area electron diffraction (SAED), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The photocatalytic activity under the ultraviolet (UV) radiation exposure and the dye adsorption under the dark condition have been measured using the methylene blue (MB) as a model catalytic dyeagent. It has been demonstrated that, the transformation of the magnetic photocatalyst to the magnetic dye adsorbent catalyst is accompanied by a change in the mechanism of dye-removal from an aqueous solution from the photocatalytic degradation to the surface adsorption under the dark condition. It has been also shown that, due to its magnetic nature, the magnetic dye adsorbent catalyst can be separated from the treated solution using an external magnetic field and the previously adsorbed dye can be removed from the surface of nanotubes via typical surface cleaning treatment, which make the recycling of the magnetic dye-adsorbent catalyst possible.