Magnetic agitation enhances effectiveness.

Photocatalytic/ magnetic composite particles have been invented as improved means of exploiting established methods of photocatalysis for removal of chemical and biological pollutants from air and water. The photocatalytic components of the composite particles are formulated for high levels of photocatalytic activity, while the magnetic components make it possible to control the movements of the particles through the application of magnetic fields. The combination of photocatalytic and magnetic properties can be exploited in designing improved air- and water-treatment reactors.

Figure 1. Photocatalytic/Magnetic CompositeParticles according to the invention can be madein different forms.

As used here, “nano-sized” refers to sizes in the range from a few nanometers to about 100 nanometers. The reason for choosing this size range is simply that experience has shown that nano-sized photocatalyst particles are more photocatalytically active than are micron- and larger-sized photocatalyst particles.

The magnetic core (or, optionally, the nano-sized magnetic particles) can be made of any of a variety of suitable magnetic materials — for example, Fe₃O₄, BaO(Fe₂O₃)₆, SrO(Fe₂O₃)₆, or AlNiCo. The protective layer can be a polymer or a ceramic — for example, poly(tetraethylfluoroethylene) or poly(methyl methacrylate) or silica. The photocatalyst can be TiO₂, ZnO, or Fe₂O₃. Nano-sized photocatalyst particles can be coated onto the larger core particles by various techniques, e.g., a dry coating machine, wherein a mixture of the two types of particles is forced to pass through a narrow clearance under high stress.