The key difference between zinc oxide and titanium dioxide is that zinc oxide (ZnO) is a better UV absorber across more wavelengths when compared to titanium dioxide (TiO2).
Zinc oxide is the oxide of zinc having the chemical formula ZnO, whereas titanium dioxide is the oxide of titanium having the chemical formula TiO2. Both zinc oxide and titanium dioxide are inorganic compounds. Both these compounds are white in colour; thus, it is difficult to identify them separately just by looking at them. However, they have very distinct chemical and physical properties.
CONTENTS
1. Overview and Key Difference
2. What is Zinc Oxide
3. What is Titanium Dioxide
4. Side by Side Comparison – Zinc Oxide vs Titanium Dioxide in Tabular Form
5. Summary
What is Zinc Oxide?
Zinc oxide is the oxide of zinc metal, having the chemical formula ZnO. It appears as a white solid. However, it occurs naturally in the form of zincite. But most of the zinc oxide we use in industry is produced synthetically. There are 3 processes for this: indirect process (French process), direct process (American process) and wet chemical process.
Figure 01: Zinc Oxide Appearance
Furthermore, this substance is insoluble in water; thus, it is useful in many applications. For example, as an additive of rubber, plastic, ceramic, glass, cement, lubricants, etc. Besides, zinc oxide is also used in ceramic industry due to its favourable properties like high heat capacity, high heat conductivity, low thermal expansion and high melting point.
Moreover, zinc oxide crystallizes in two main forms: hexagonal structure and cubic structure. The Mohs scale hardness for this material is 4.5. Also, it is an amphoteric oxide. Though it is insoluble in water, it dissolves in most acids. Sometimes, solid zinc oxide can dissolve in alkalis as well. It gives soluble zincates.
What is Titanium Dioxide?
Titanium dioxide is the oxide of titanium metal, and it has the chemical formula TiO2. It appears as a white solid and is insoluble in water. Also, it is a naturally occurring oxide of titanium metal; this mainly occurs in three forms as ilmenite, rutile and anatase.
Figure 02: Titanium Dioxide Appearance
In the production process, the most often used material is ilmenite. Rutile also can be used as a source, and we can get titanium dioxide via the chloride process. More importantly, we can convert ilmenite into pigment grade titanium dioxide. There are two methods for this: sulfate process and chloride process.
Moreover, titanium dioxide as a pigment is the main form that has wide applications. It is due to its brightness and high refractive index. We can use this pigment to provide whiteness and opacity for paints, coatings, plastics, paper, food, medicine, toothpaste, etc. Furthermore, it is a component of sunscreens because of its strong UV light absorbing capability.
What is the Difference Between Zinc Oxide and Titanium Dioxide?
Zinc oxide is the oxide of zinc having the chemical formula ZnO, whereas titanium dioxide is the oxide of titanium having the chemical formula TiO2. When considering the chemical formulas, zinc oxide has one oxygen atom per metal atom where titanium dioxide has two oxygen atoms per titanium atom.
Furthermore, the key difference between zinc oxide and titanium dioxide is that the zinc oxide is a better UV absorber across more wavelengths, while titanium dioxide is not a good absorber of UV rays since its UV absorption spectrum is not as broad. Moreover, when considering toxicity and safety, zinc is a mineral nutrient we need while titanium is a toxic heavy metal; therefore, zinc oxide is much safer than titanium dioxide. Therefore, this is a vital difference between zinc oxide and titanium dioxide.
Summary – Zinc Oxide vs Titanium Dioxide
Zinc oxide and titanium oxide are the most stable oxides of the metals zinc and titanium. However, there is a distinct difference between zinc oxide and titanium dioxide, mainly in terms of their properties. Zinc oxide is a better UV absorber across more wavelengths when compared to titanium dioxide. Moreover, zinc oxide is much safer than titanium dioxide as the latter is a toxic heavy metal.
Reference:
1. Mckeen, Laurence W. Fatigue and Tribological Properties of Plastics and Elastomers. Elsevier, 2016.
2. Mohapatra, Shyam S., et al. Nanocarriers for Drug Delivery: Nanoscience and Nanotechnology in Drug Delivery. Elsevier, 2019.
Image Courtesy:
1. “Zinc oxide” By w:User:Walkerma – Own work (Public Domain) via Commons Wikimedia
2. “Titanium(IV) oxide” By The original uploader was Walkerma at English Wikipedia. – Transferred from en.wikipedia to Commons (Public Domain) via Commons Wikimedia