Photoreactor with self-contained photocatalyst recapture

A photoreactor system, comprising:

• a generally upright outer cylinder;
• an inner cylinder disposed generally coaxially within the outer cylinder and defining an annular reaction zone therebetween, the inner cylinder having an inlet at a bottom thereof for allowing inflow of buoyant photocatalyst particles, and an orifice disposed at a top thereof for allowing outflow of the buoyant photocatalyst particles into downwardly flowing liquid in the reaction zone;
• means for directing light into the reaction zone, whereby the photocatalyst particles may induce photo-chemical reactions within the liquid;
• and
• a flotation chamber communicating with and disposed at a bottom of the outer cylinder and configured to substantially reduce the flow velocity of the liquid upon exiting the annular reaction zone to a velocity wherein the buoyant photocatalyst particles are allowed to float upward through the inlet of the inner cylinder.

A method of recapturing photocatalyst particles in a liquid, comprising:

• flowing a liquid downwardly through a reaction zone;
• introducing buoyant photocatalyst particles into the downwardly flowing liquid, such that the photocatalyst particles are drawn downward through the reaction zone with the flowing liquid;
• and
• recycling the particles through a catalyst recovery chamber by reducing the downward flow velocity of the liquid beyond a bottom of the reaction zone, such that the buoyant photocatalyst particles are allowed to float upward through the catalyst recovery chamber to the reaction zone for reintroduction into the downwardly flowing liquid.