What does activation means and do ? (eg activated bauxite)

[Mebing]

What does activated bauxite, activated carbon, activated alumina do to these materials? How is it achieved? Is it by burning or heating up to certain temperature?

On the other hand, what does calcine / calcination means?

 

[25362]

Some dictionary-type definitions:

activation: in chemistry, treatment of a substance by radiation, heat, or a reagent to produce a more rapid or complete chemical or physical change.

activated carbon (aka charcoal): powder, granular or pelleted form of amorphous non-graphitic carbon characterized by a very large surface area per unit volume because of the large number of pores. Can be activated, depending on the starting material, either chemically, helped by calcination, or by selective oxidation. The oxidation is carried out with air at low temperature, or steam, or CO2, or flue gas at high temperatures. Commercial grades are either gas-phase or liquid-phase adsorbents.

activated bauxite:crushed, screened and calcined bauxite, in particles that range from 20-60 and for 30-60 mesh grades; used in ore refining for filtering; aka filter bauxite.

activated clay: a special grade of absorbent/adsorbent fine-graded acid-treated clay used as filtering medium in refineries for removing solids or colorizing matter from lube oils and waxes.

fuller's earth: a fine-graded , natural, earthy material, such as clay, with a high adsorptive power, consisting principally of hydrated aluminum silicates; used as an adsorbent in refining and decolorizing oils and waxes, as a catalyst, and as a bleaching agent.

calcination: a process in which a material is heated below its melting point to effect a thermal decomposition (of hydrates, carbonates, etc.) expelling the volatiles, or to promote a phase transition other than melting.