In water purification we can use various methods that both absorb and adsorb toxins or other contaminants.

Absorption is the process by which a liquid is dissolved by a liquid or solid. By adsorption, atoms, ions or molecules attach from a substance to a surface of the adsorbent and can easily be removed.

An example of both processes is the use of activated carbon. The ability of activated carbon to attract and hold unwanted materials (absorption) is based on a large number of pores. The carbon particles form a large surface area to which colored molecules can adhere (adsorption). When the medium (activated carbon) is saturated with various substances, absorbed and adsorbed on the inside and outside, it is no longer effective and must be replaced.

This is done by either letting the water flow through a filter with activated carbon, or through a filter with a special type of adsorption resin. With adsorption resin, in combination with brine (osmotic shock), the filter can be backwashed. The unwanted material will then be flushed down the drain.