A material similar to molecular sieve material. It has a large internal surface area and good thermal conductivity. It is typically supplied in pellets of 1 mm to 2 mm diameter and roughly 5 mm length or as grains of the order 1 mm. Occasionally as beads up to 5 mm diameter. They are typically made from aluminium oxide with a porous structure.
Materials used to absorb other materials due to their high affinity for doing so. Examples:
A sponge absorbs many times its own weight in water.