Filter element for decomposing contaminants, system for decomposing contaminants and method using the system

1. A filter element for decomposing contaminants comprising:

a substrate; and

a photocatalytic mixture comprising at least a photocatalyst and a co-catalyst;

wherein the photocatalyst comprises WO 3 and the co-catalyst comprises CeO 2 , and

wherein the molar ratio of WO 3 to CeO 2 is 1:5 to 5:1.

2. The filter element as claimed in claim 1 , wherein the substrate is a gas permeable support.

3. The filter element as claimed in claim 1 , wherein the photocatalyst shows visible light responsiveness.

4. The filter element as claimed in claim 1 , wherein said photocatalyst further comprises TiO 2 or Ti(O,C,N) 2 :Sn.

5. The filter element as claimed in claim 1 , wherein said co-catalyst further comprises anatase TiO 2 , SrTiO 3 , KTaO 3 , or KNbO 3 .

6. The filter element as claimed in claim 1 , wherein said co-catalyst further comprises In 2 O 5 , Ta 2 O 5 , anatase TiO 2 , rutile TiO 2 , or a combination of anatase and rutile TiO 2 .

7. The filter element as claimed in claim 1 , which further comprises a fluororesin porous layer laminated on at least one surface of the substrate, wherein the photocatalytic composition is disposed on the fluororesin porous layer.

8. The filter element as claimed in claim 7 , wherein a fluororesin constituting the fluororesin porous layer contains polytetrafluoroethylene.

9. The filter element as claimed in claim 7 , wherein the photocatalytic composition is formed on the fluororesin porous layer through an aerosol deposition method.

10. The filter element as claimed in claim 1 , wherein the photocatalytic composition further comprises a dopant.

11. The filter element as claimed in claim 10 , wherein the molar ratio of co-catalyst to dopant is 99.9:0.1 to 80:20.

12. The filter element as claimed in claim 10 , wherein the dopant is at least one of carbon, nitrogen, sulfur, fluorine, tin, zinc, manganese, aluminum, selenium, niobium, nickel, zirconium, cerium, or iron.

13. The filter element as claimed in claim 1 , wherein the molar ratio of WO 3 to CeO 2 is 1:4 to 4:1.

14. The filter element as claimed in claim 1 , wherein the substrate is a porous substrate.

15. A system for decomposing contaminants comprising:

the filter element of claim 1 and

a source of electromagnetic radiation that is in optical communication with said photocatalytic composition.

16. The system as claimed in claim 15 , wherein said substrate defines a volume.

17. The system as claimed in claim 15 , further comprising an enclosing element, wherein said substrate is disposed within said enclosing element.

18. The system as claimed in claim 15 , further comprising an airflow element for creating an airflow, said airflow element being disposed within said enclosing element.

19. A method comprising the steps of:

placing a system as claimed in claim 15 in atmospheric communication with an ethylene-sensitive plant; and

reducing the amount of ethylene to a concentration below a threshold by contacting ethylene with the photocatalytic composition while said photocatalytic composition is illuminated by electromagnetic radiation comprising a wavelength sufficient to activate the photocatalytic composition.

20. The method as claimed in claim 19 , further comprising the step of:

maintaining the concentration of ethylene below said threshold.