Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Soak it in a 50/50 bleach-water solution for 24 hours, or as long as it takes to return the Purigen particles to their original white coloration.
Then rinse with fresh water several times, and let it sit in fresh 'conditioned' water until you're ready to use it again - no need for the buffer or any other steps.