What is the Difference Between Fumed Silica and Precipitated Silica

The key difference between fumed silica and precipitated silica is that fumed silica is usually small in size, whereas precipitated silica is usually larger in size.

Fumed silica is a type of silica produced in flame. It consists of microscopic droplets of amorphous silica fused into branched chainlike 3D secondary particles that can get agglomerated into tertiary particles. Precipitated silica is a type of silica that is amorphous and appears as a white, powdery material.

CONTENTS

1. Overview and Key Difference
2. What is Fumed Silica  
3. What is Precipitated Silica
4. Fumed Silica vs Precipitated Silica in Tabular Form
5. Summary – Fumed Silica vs Precipitated Silica 

What is Fumed Silica?

Fumed silica is a type of silica produced in flame. It consists of microscopic droplets of amorphous silica fused into branched chainlike 3D secondary particles that can get agglomerated into tertiary particles. It is also known as pyrogenic silica.

This fumed silica powder has an extremely low bulk density and a large surface area. The structure is 3 dimensional, which allows an increase in viscosity and thixotropic behavior upon using it as a thickener or reinforcing filler.

When considering the important properties of fumed silica, it has a very strong thickening effect. Primarily, the particle size is 5-50 nm. These particles are nonporous, and they have a surface area of around 50-600 m2/g.

The method used for fumed silica production is flame pyrolysis of silicon tetrachloride or quartz sand that is vaporized in a 3000 Celsius degrees electric arc. The most common global producers of fumed silica are Evonik, Cabot Corporation, and Wacker Chemie.

What is Precipitated Silica?

Precipitated silica is a type of silica that is amorphous and appears as a white, powdery material. This material is produced through precipitation from a solution consisting of silicate salts. There are three major types of amorphous silica as pyrogenic silica, precipitated silica, and silica gel. However, precipitated silica has the greatest commercial significance. Unlike pyrogenic silica, precipitated silica is not essentially microporous.

Usually, precipitated silica production starts with the reaction of a neutral silicate solution with a mineral acid. We need to add sulfuric acid and sodium silicate solutions simultaneously with agitation to water. Moreover, we can carry out precipitation in acidic conditions. We need to avoid the formation of a gel by stirring it at elevated temperatures.

When considering the properties of precipitated silica, they are porous, and the diameter ranges between 5-100 nm. The specific surface area ranges between 5-100 m2/g. There are different important applications such as using as a filler, softener, for cleaning, thickening, and polishing agents, for food processing, pharmaceutical productions, etc.

What is the Difference Between Fumed Silica and Precipitated Silica?

Fumed silica is a type of silica produced in flame. It consists of microscopic droplets of amorphous silica fused into branched chainlike 3D secondary particles that can get agglomerated into tertiary particles. Precipitated silica is a type of silica that is amorphous and appears as a white, powdery material. The key difference between fumed silica and precipitated silica is that fumed silica is usually small in size, whereas precipitated silica is usually larger in size.

The below infographic presents the differences between fumed silica and precipitated silica in tabular form for side by side comparison.

Summary – Fumed Silica vs Precipitated Silica

Silica is silicone dioxide. There are different forms of silica, such as fumed silica and precipitated silica. The key difference between fumed silica and precipitated silica is that fumed silica is usually small in size whereas precipitated silica is usually larger in size.

Reference:

1. “Fumed Silica.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Sio2 130m2 per gram under blue book 1600dpi” By Achim Hering – Own work (CC BY 3.0) via Commons Wikimedia
2. “Fumed silica process” By MagentaGreen – Own work (CC BY-SA 3.0) via Commons Wikimedia