Production

The production of precipitated silica starts with the reaction of an alkaline silicate

Silicate

A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...

 solution with a mineral acid

Mineral acid

A mineral acid is an acid derived from one or more inorganic compounds. A mineral acid is not organic and all mineral acids release hydrogen ions when dissolved in water.-Characteristics:...

. Sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 and sodium silicate

Sodium silicate

Sodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles...

 solutions are added simultaneously with agitation to water. Precipitation

Precipitation (chemistry)

Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...

 is carried out under alkaline conditions. The choice of agitation, duration of precipitation, the addition rate of reactants, their temperature and concentration, and pH can vary the properties of the silica. The formation of a gel stage is avoided by stirring at elevated temperatures. The resulting white precipitate is filtered, washed and dried in the manufacturing process.

Na₂(SiO₂)_3.3(aq) + H₂SO₄(aq) → 3.3 SiO₂(s) + Na₂SO₄(aq)

Properties

The particles are porous. Primary particles with a diameter of 5 - 100 nm, and specific surface area 5-100 m²/g. Agglomerate

Agglomerate

Agglomerates are coarse accumulations of large blocks of volcanic material that contain at least 75% bombs...

 size is 1 - 40 µm with average pore size is > 30 nm. Density: 1,9 - 2,1 g/cm³.

Applications

• Filler
  Filler
  In general, a filler is something that is used to fill gaps. Specialized meanings of the word "filler" include:* Filler , dietary fiber and other ingredients added to pet foods to provide bulk...
  
  , softener
  Softener
  Softener may refer to:* Water softener* Fabric softener* Stool softener* Food softener* Plastic softener, generically known as a Plasticizer...
  
   and performance improvement in rubber
  Rubber
  Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
  
   and plastics
• Cleaning, thickening and polishing agent in toothpastes for oral health care
• Food processing
  Food processing
  Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...
  
   and pharmaceuticals additive as anti caking, thickening agent, absorbent to make liquids into powders.
• Food rheology
  Food rheology
  Food rheology is the study of the rheological properties of food, that is, the consistency and flow of food under tightly specified conditions. The consistency, degree of fluidity, and other mechanical properties are important in understanding how long food can be stored, how stable it will...
  
   modifier
• Defoamer
  Defoamer
  A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably....
  
  component.