In one process of water purification, for example, aluminum sulfate, Al ₂ (SO ₄ ) ₃ , or alum (usually potassium aluminum sulfate , KAl(SO ₄ ) ₂ ), is mixed with lime ( calcium hydroxide, Ca(OH) ₂ ) in a container of water to be purified. The reaction between these compounds results in the formation of a gelatinous precipitate aluminum hydroxide. As the precipitate settles out of solution , it adsorbs on its surface particles of dirt and bacteria that were suspended in the impure water, which can then be removed by filtering off the aluminum hydroxide precipitate.

It is used in a number of chemical operations, for example, as a filtering medium and in ion-exchange and chromatography devices.

Aluminum hydroxide is popular as an antacid. to bring relief from "heartburn." A few of the more common commercial antacids containing aluminum hydroxide are Amphojel, Di-Gel, Gelusil, and Maalox.

Aluminum hydroxide is also used as a mordant in dyeing and manufacture of certain paint pigments.

Additional uses of aluminum hydroxide include the manufacture of aluminosilicate glass, a high melting point glass used in cooking utensils, the waterproofing of fabrics, and the production of fire clay, paper, pottery, and printing inks.