Colloidal silicon dioxide is commonly utilized as an agent in pharmaceutical and food products. Manufacturers in various other sectors also utilize silicon since it is readily available and adaptable. This article focuses on the properties and applications of colloidal silicon dioxide.
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What is Colloidal Silicon Dioxide?
Colloidal silicon dioxide, in other terms known as ‘colloidal silica’, is a polymeric form of silicon. The non-toxic, naturally occurring element silicon is listed in the periodic-table and is widely employed in the industry.
It is abundant in nature because it accounts for a sizeable portion of the Earth's crust and is the second most prevalent element after oxygen. The water-based suspensions of crystalline silicon dioxide particles are known as colloidal silicon dioxide (SiO2).
These amorphous silica fragments are generated by the alkaline polymerization of silicon dioxide nuclei from silicate mixtures to create nanoscale silicon dioxide sols with a large surface area.
The silicon dioxide nanoparticle surface is then charged, enabling the particles to repel and create a stable dispersion or colloid. The stable dispersion formed is called colloidal silicon dioxide and has unique properties which can be applied to different applications.
Properties of Colloidal Silicon Dioxide
The types of colloidal silicon dioxide generated vary in a number of aspects or qualities. Particle-size distribution may vary from small to broad depending on the production process, and the typical range of particle size is 5–40 nm.
Colloidal silicon dioxide has the physical characteristics of light, loose, bluish-white-colored, flavorless, and amorphous powder. Conventional colloidal silicon dioxide consists of a negative (anionic) surface charge that is regulated with ammonium or sodium and is stable at a potential hydrogen (pH) range of 8 to 10.5.
Strong absorbability, a sizable surface area, and excellent flow behavior are a few of the excellent physicochemical properties of colloidal silicon dioxide.
The adjustable chemistry of the silanol-rich surface of the particles gives colloidal silicon dioxide additional properties, including hardness and high binding ability.
Another characteristic is colloid purity, which varies depending on the manufacturing procedure and ranges from a few ppb to hundreds of ppm of total contaminant concentration.
How Can Colloidal Silicon Dioxide be fabricated?
Sol-gel, hydrothermal, and chemical vapor deposition (CVD) methods have been used to fabricate colloidal silicon dioxide.
The sol-gel process is widely utilized to make pure silicon dioxide particles because of its capacity to regulate the physical appearance by methodical monitoring of reaction variables under ambient temperature.
The ion-exchange procedure is a part of the technique used to produce colloidal silicon dioxide using sodium silicate through the sol-gel method. With this technique, particle size and distribution of colloidal silicon dioxide may be easily controlled.
The technique also provides improved electric charge and high zeta for colloidal silicon dioxide particles. This makes the solution more stable, repelling aggregation and preventing agglomeration between particles.
Batllo et al., in the research titled ‘Colloidal silica: chemistry, properties and adaptations for electronic polishing applications’ reported the organic route for manufacturing colloidal silicon dioxide.
The organic route entails a number of steps designed to generate a silicon alkoxide which is hydrolyzed to colloidal silicon dioxide. Following solvent exchange, the resultant alcohol-based product is converted to an aqueous silicon dioxide solution.
The stöber method can also be used to produce colloidal silicon dioxide. The ammonia-induced hydrolysis and condensing of tetra-ethyl-orthosilicate (TEOS) in a water-based alcohol (typically ethanol) liquid is used in the fabrication.
Peptization is another fabrication method to manufacture colloidal silicon dioxide. Colloidal silicon dioxide is made via peptizing a hydro-wet gel derived from sodium-silicate fluid in a mix of pure water (H2O) and nitric acid (HNO3).
Lee et al. observed that colloidal silicon dioxide generated via peptization had a homogeneous particle size of about 20 nm. In addition, heat treatment is employed to decrease the density of the exterior silanol groups, rendering colloidal silicon dioxide more stable.
Industrial Applications Of Colloidal Silicon Dioxide
Colloidal silicon dioxide has potential use in medicine (drug-resistant bacterial biofilms), textile, casting, and stiffener in hard coating reagents. Micro-particles of colloidal silicon dioxide have recently been used to manufacture paper. To prevent particles from forming larger agglomerates, a steady dispersion is crucial for producing paper.
Colloidal silicon dioxide is not soluble in water and, therefore, inert. As a result, it is employed as a covering or coating agent for dietary supplements and pharmaceutical pills. The trade name for a commercially accessible medical-grade colloidal silicon dioxide is “Aerosil”.
Colloidal silicon dioxide is commonly found in food products. This is because it can operate as a freely flowing agent. It is present in salt and bicarbonate of sodium (baking soda). It is also present in herbs and spices and a variety of other food products that require an anti-caking ingredient.
LUDOX® colloidal silica is another colloidal silicon dioxide-based product that is utilized in a variety of applications, such as a fining agent in the production of beer and wine and a high-temperature binder in the fabrication of aerospace parts.
Colloidal silicon dioxide can also be employed as a thickening additive in dyes, shampoos, and cosmetics. It is commercially available as "Cab-o-Sil" (thickening agent).
Research Applications Of Colloidal Silicon Dioxide
There has been a significant amount of research and development work dedicated to investigating novel uses of colloidal silicon dioxide.
Sahiner et al. recently described the practical application of colloidal silicon dioxide (SiO2) granules as a substitute catalyst for renewable energy carriers in the methanolysis of NaBH4 for H2 generation.
Mesoporous silica (MPS) is a type of synthetically engineered colloidal silicon dioxide with highly structured pores on the mesoscale (2-50 nm). Owing to their large surface area, tunable pore size and volume, MPS have gained attention in applications, including drug/protein/gene delivery and tissue engineering.
Lee et al. discovered that MPS (altered colloidal silicon dioxide) nanoparticles reduced the expression of inflammatory cytokines in macrophages, including interleukin-6 (IL-6).
These findings suggest that MPS (colloidal silicon dioxide) could be used in biological and biotechnological applications.
Colloidal silicon dioxide products are non-agglomerated, nanosized, spherical and stable silicon dioxide dispersions.
The chemical modification of colloidal particles allows for control of their shape, stability, mechanical, chemical, and physical properties. As a result, colloidal silicon dioxide is favored for a wide range of applications.
Recently, scientific and analytical efforts have been concentrated on creating colloidal silicon dioxide products using modified and novel fabrication processes to improve their present qualities. This is being done for colloidal silicon dioxide to be utilized in unexplored industrial or research fields.
References and Further Reading
Allen H. et al. (1996) The Colloidal Stability and Surface Chemistry of Stöber Silica.
Lee S. et al. (2011) The comparative effects of mesoporous silica nanoparticles and colloidal silica on inflammation and apoptosis. Biomaterials. 1;32(35), pp.9434–43.
Sahiner N. & Yasar A.O. (2016) A New Application for Colloidal Silica Particles: Natural, Environmentally Friendly, Low-Cost, and Reusable Catalyst Material for H2 Production from NaBH4 Methanolysis. Industrial & Engineering Chemistry Research. 2;55(43), pp.11245–52.
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What Is Colloidal Silicon Dioxide? | Sciencing [Internet]. [cited 2023 Jul 28]. Available from: https://sciencing.com/colloidal-silicon-dioxide-8725504.html
Batllo F. et al. (2018). Colloidal silica: Chemistry, properties and adaptations for electronic polishing applications. China Semiconductor Technology International Conference, CSTIC 2018. 2018 May 29; pp.1–4.
Lee Y. K. et al. (2000) Preparation of colloidal silica using peptization method. Colloids and Surfaces A: Physicochemical and Engineering Aspects 10;173(1–3), pp. 109–16.
AEROSIL® [Internet]. [cited 2023 Jul 28]. Available from: https://www.l-i.co.uk/products/aerosil-fumed-silica
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