Filter
A filter includes a filter medium having an average pore size of 1 to 5 mm, and photocatalyst particles deposited on the filter medium. The photocatalyst particle contains a titanium compound particle and a metal compound bonded to the surface of the titanium compound particle with an oxygen atom. The metal compound contains a metal atom and a hydrocarbon group. The titanium compound particle has absorption at wavelengths of 450 nm and 750 nm in the visible absorption spectrum of the titanium compound particle.
1. A filter comprising:
a filter medium having an average pore size of 1 mm to 5 mm; and
photocatalyst particles deposited on the filter medium,
each photocatalyst particle containing a titanium compound particle and a metal compound bonded to a surface of the titanium compound particle with an oxygen atom,
the metal compound containing a metal atom and a hydrocarbon group,
the titanium compound particle having absorption at wavelengths of 450 nm and 750 nm in a visible absorption spectrum of the titanium compound particle.
2. The filter according to claim 1 ,
wherein the photocatalyst particle has absorption over an entire wavelength range of 400 nm to 800 nm in a visible absorption spectrum of the photocatalyst particle.
3. The filter according to claim 1 ,
wherein the photocatalyst particle has an absorption peak at 2700 cm to 3000 cm −1 in an infrared absorption spectrum of the photocatalyst particle.
4. The filter according to claim 1 ,
wherein the photocatalyst particles are at least one type of particles selected from the group consisting of metatitanic acid particles, titanium oxide particles, titanium oxide aerogel particles, and silica-titanic composite aerogel particles.
5. The filter according to claim 1 ,
where the photocatalyst particles have an average size of 0.01 μm to 0.5 μm.
6. The filter according to claim 1 ,
wherein the photocatalyst particles have an average size of 0.02 μm to 0.15 μm.
7. The filter according to claim 1 ,
wherein a ratio of the average size of the photocatalyst particles to an average pore size of the filter medium (average particle size/average pore size) is 0.002×10 −3 to 0.5×10 −3 .
8. The filter according to claim 1 ,
wherein a ratio of the average size of a photocatalyst particles to an average pore size of the filter medium (average particle size/average pore size) is 0.004×10 −3 to 0.15×10 −3 .
9. The filter according to claim 1 ,
wherein the photocatalyst particle contains a metatitanic acid particle.
10. The filter according to claim 1 ,
wherein the filter medium is composed of a ceramic material.
11. The filter according to claim 1 ,
wherein a transmittance of visible light through the filter is 10% to 70%.
12. The filter according to claim 1 ,
wherein the filter medium has an optical reflectance of 10% to 90%.
13. The filter according to claim 1 ,
wherein an L* value of the filter medium in the CIE 1976 L*a*b* colorimetric system is 35% to 95%.