ABSTRACT
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 and hematite, and pure cobalt ferrite) 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 X-ray and selected-area electron diffraction, transmission electron microscope, and vibrating sample magnetometer. The photocatalytic activity under the ultraviolet-radiation exposure and the dye-adsorption under the dark-condition have been measured using the methylene blue as a model catalytic dye-agent. 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.
