Purigen is great stuff, and recharging is straight forward like they posted above.
But, just for you

, courtesty Seachem:
Rinse before use. Use in a fine mesh filter bag. Each 1 L treats up to 4,000 L (1,000 gallons*) for up to six months. Exhaustion is indicated by a pronounced discoloration of the beads to dark brown or black.
Regeneration: Soak in a 1:1 bleach:water solution for 24 hours in a non-metalic container in a well ventilated area and away from children. Rinse well, then soak for 8 hours with a solution containing 2 tablespoons of
ChlorGuard™,
Prime®, or equivalent dechlorinator per cup of water. Rinse well. Original color and full activity should now be restored and Purigen® is ready for reuse. Caution: some slime coat products may permanently foul Purigen® and render regeneration difficult. Do not reuse if odor of chlorine is detectable. In case of doubt, soak beads in small quantity of water and test for residual chlorine with a chlorine test kit.