Silica, or silicon dioxide (SiO2) in its pure form is colorless to white.  Rhodia’s silicas are amorphous precipitated silicas obtained from a process using essentially sand, which is the most abundant mineral present in the earth’s crust.

Rhodia manufactures amorphous precipitated silica by dissolving sand followed by re-precipitation. The silica thus formed is a synthetic silica which is amorphous in nature and is consequently totally harmless: it is used in animal and human nutrition. Rhodia only manufactures amorphous precipitated silicas which are available in standard or high performance grades.

Non-crystalline, or amorphous silica, is usually prepared by vapor-phase hydrolysis, precipitation or other processes that ensure the absence of crystalline silica.

In precipitated silica, the reaction mixture is held in the alkaline pH region, and offers limited aggregates of primary particles with a diameter of >5 n/m., and specific surface area (<350 m2/g). The production of precipitated silica starts with the reaction of an alkaline silicate solution with a mineral acid. Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. The resulting white precipitate is filtered, washed and dried. Precipitated silica's basic characteristics, which can be altered during the precipitation process, are particle size distribution, porosity, specific surface area and purity.

Precipitated silica is a safe amorphous (non-crystalline) mineral. According to the relevant United States and European Union standards, precipitated silica is non-hazardous with regard to manufacture, transportation and handling: it is an inert powder, considered non-toxic for humans.

Rhodia Silica Systems manufactures three main types of synthetic precipitated silicas:

• standard precipitated silica;
• precipitated silica for toothpaste (Oral-Care) and animal feed and human foodstuff (Nutraceutics) applications,  which require particular specifications;
• high performance precipitated silica which brings added value to our customers by facilitating their processes and enhancing the performance of their products.