Sodium aluminate is an inorganic chemical used as an effective source of aluminum hydroxide in many industrial and technical applications. Pure sodium aluminum (anhydrous) is a white crystalline solid with various given NaAlO formula 2, NaAl (OH) 4 (hydrated), Na 2 O·Al 2 ö 3, or Na 2 Al 2 Ò 4. Sodium aluminate is commercially available in solution or solid form.
Other related compounds, sometimes called sodium aluminate, are prepared by reaction of Na 2 ö and Al 2 ö 3 as Na 5 AlO 4 containing discrete AlO 4 5-anions, sodium 7 Al 3 ö 8 and Na 17 Al 5 ö 16 contains complex polymer anions, and NaAl 11 ö 17, once mistaken for β alumina, phase alumina.
Anhydrous sodium aluminate NaAlO 2 contains a three-dimensional framework of corner-connected AlO 4 tetrahedra. The hydrated form of NaAlO 2 5/4H 2 O has layers of AlO 4 tetrahedrons connected into a ring. These layers are held together by sodium ions and water molecules. The water molecules form hydrogen bonds with the O atoms in the AlO 4 tetrahedra.
Sodium aluminate is manufactured by dissolving aluminum hydroxide (Al(OH) 3) in a caustic soda (NaOH) solution. At temperatures close to the boiling point, aluminum hydroxide (gibbsite) can be dissolved in 20-25% NaOH aqueous solution. Using a more concentrated NaOH solution will produce a semi-solid product. The process must be carried out in a steam-heated nickel or steel vessel. Aluminum hydroxide should be boiled with about 50% caustic soda in water until a pulp is formed. The final mixture must be poured into a tank and cooled; a solid substance containing about 70% NaAlO 2 is then formed. After this product is crushed, it is dehydrated in a rotary oven. The resulting product contains 90% NaAlO 2 and 1% water, and 1% free NaOH.
In water treatment, it is used as an auxiliary and coagulant in water softening systems to improve flocculation and remove dissolved silica and phosphate.
In construction technology, sodium aluminate is used to accelerate the solidification of concrete, mainly to work during frost.
Sodium aluminate is also used in paper industry, refractory brick production, alumina production, etc.
Sodium aluminate solution is an intermediate in the production of zeolite.