There are two closely sounding terms - adsorption and absorption - that have very different meanings.
Absorption is like when food is taken into the cells of the body and even when a sponge picks up water.
Adsorption refers to when one substance sticks to the surface of another substance. Adsorption is very important in chemical reactions when catalysts are used. The chemicals that are reacting stick, or adsorb, to the surface of the catalyst and the chemical reaction can then take place more efficiently.
after digestion,food molecules are small and soluble. they are able to move through the walls of the intestine into the blood by diffussion , osmosis or active transport. most absorption takes place in the ileum. its inner wall is lined with finger-like projections called villi which greatly increase the surface area. the wall of the villus is only one cell thick, making it easy for the products of digestion to be absorbed.
therefore absorption is when molecules of one substance is taken directly into another substance.
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the adsorbent. It differs fromabsorption, in which a fluid permeates or is dissolved by a liquid or solid. The term sorption encompasses both processes, whiledesorption is the reverse of adsorption.