What is the Difference Between Colloidal Silica and Reactive Silica?Ĭolloidal and reactive silica are two forms of silicon present in the water supply. Such methods include lime softening, ion exchange, reverse osmosis, ultrafiltration, and electrocoagulation. There are different methods we can use to remove reactive silica from a water supply. In other words, reactive silica is the non-polymeric form of silica. Reactive silica is any monomeric silica, including the ionized forms and potentially any dissolved dimer of silicon. There are many different applications of colloidal silica, including papermaking where it is used as a drainage aid, in nanomedicine production, in producing high-temperature binders, investment casting, carbonless paper, in catalysis, as a moisture absorbent, etc. We can call this type of silica as precipitated silica or silica sols. However, if we keep the pH slightly on the alkaline side (above pH=7), then the silica particles remain separated and tend to grow gradually.

If we add a salt to the colloidal silica suspension (or if the pH is reduced below 7), the silica particles in the suspension tend to fuse with each other, forming chains. However, the initial acidification of water-glass solution (sodium silicate solution) yields silicon hydroxide, Si(OH)4. Combination of these subunits depends on the conditions of polymerization that is present in the colloidal suspension. Generally, silica particle subunits are in the size range of 1 to 5 nm. We can prepare colloidal silica via a multi-step process in which an alkali silicate solution is partially neutralized, leading to the formation of silica nuclei. Therefore, we can describe colloidal silica as a hydrophilic substance which is capable of forming hydrogen bonds.įigure 01: Silica Particle Surface in Water

When silica particles are in the water, the surface of colloidal silica in contact with water is covered by siloxane bonds and silanol groups. The silica structure in this suspension can be described as amorphous, nonporous, and typically spherical silica particles. Side by Side Comparison – Colloidal Silica vs Reactive Silica in Tabular FormĬolloidal silica is a suspension of silica particles in the liquid phase. Typically, silica in water supply exists in two forms: reactive silica and colloidal silica. This substance forms when silicon and oxygen react with each other and another metal or mineral.

Silica or silicon dioxide is a crystalline compound that is common in most rocks, mineral, and sand. The key difference between colloidal silica and reactive silica is that colloidal silica is the polymeric form of silicon, whereas reactive silica is the non-polymeric form of silicon.

Silica in water