Shining Light on Titanium Dioxide: Science behind its Manufacturing and Applications

Titanium Dioxide is everywhere you look! This wonder material is the most widely used white pigment on the planet, hiding in everything from the paint on your walls to the sunscreen on your nose. But what exactly is it, and how does it find its way into so many of our everyday products?

In this blog post, we’ll delve into the fascinating world of Titanium Dioxide. We’ll explore its unique properties, like its high refractive index that makes things bright and white and uncover its surprising applications in everything from food coloring to cosmetics. We well be also imparting the intricate details in the manufacturing process of Titanium Dioxide.

Introduction

Titanium Dioxide (TiO2) is a widely recognized bright white substance, primarily employed as a vivid colorant across various everyday items. Beyond its common usage, it possesses numerous lesser-known attributes that render it a highly valuable ingredient in our efforts to combat climate change and mitigate skin cancer risks. TiO2, an inorganic compound utilized for nearly a century, boasts non-toxic, non-reactive, and luminous properties crucial for enhancing the whiteness and brightness of diverse materials. Notably, it stands out as one of the brightest and whitest pigments, renowned for its reflective abilities and its capacity to both scatter and absorb UV rays.

• Brilliant: TiO2 exhibits unparalleled brilliance, color strength, opacity, and pearlescence unmatched by any other substance. Its unique properties make it a sought-after choice for achieving vibrant and visually striking results in various applications.
• Resistant: With exceptional resistance to heat, light, and weathering, TiO2 plays a vital role in preventing the degradation of paints and films, as well as the embrittlement of plastics. Its resilience ensures longevity and durability in a wide range of materials, even under harsh environmental conditions.
• Protective: The ability of TiO2 to scatter and absorb UV radiation makes it an indispensable ingredient in sunscreen formulations. By effectively shielding the skin from harmful UV rays, TiO2 aids in the prevention of skin damage and reduces the risk of cancer, highlighting its crucial role in sun protection.
• Powerful: TiO2 serves as a potent photocatalyst, particularly in solar panels, harnessing solar energy for various applications. Additionally, it exhibits the capability to reduce pollutants in the air, contributing to environmental remediation efforts and promoting cleaner air quality, showcasing its versatility and impact beyond traditional uses.

Manufacturing Process

Two primary methods, the Sulfate Process and the Chloride Process, utilize the principal ores ilmenite and rutile, respectively, for the manufacturing of Titanium Dioxide. Ilmenite typically contains 45-60% TiO2, while rutile can contain up to 99% TiO2. Although these ores are mined globally, the majority of production occurs in Australia and South Africa. Major Titanium Dioxide producers balance their production between these two processes, with both yielding the oxide in rutile crystal form. However, the Sulfate Process can also produce an alternative form, anatase, suited for specialized applications. While the Sulfate Process operates as a batch process, the Chloride Process runs continuously. Approximately 65% of the world’s Titanium Dioxide production is estimated to be based on the Chloride Process.

The Chloride Process

The Chloride process commences by blending raw materials with gaseous chlorine within a fluidized bed reactor, operating at temperatures approximately between 900˚C to 1000˚C, with coke serving as a reducing agent. This process yields a gas stream comprising titanium tetrachloride (TiCl4), carbon oxides, and all impurity metals present in the feedstock in the form of metal chlorides. However, certain impurities like silica and zirconium may not undergo chlorination and consequently accumulate within the reactor.

The Chloride process for producing Titanium Dioxide involves several key steps:

• Purification: The initial gas stream containing titanium tetrachloride (TiCl4) is cooled and treated to remove impurities like metal chlorides. These impurities solidify and are separated, leaving highly purified TiCl4.

• Conversion: The purified TiCl4 is further cooled and condensed into a liquid state. This liquid is then fed into a high-temperature reactor (above 1500°C) where it reacts with oxygen. This reaction produces Titanium Dioxide (TiO2) and releases chlorine gas, which is recycled back to the beginning of the process.

• Cleaning and Finishing: Residual chlorine clinging to the TiO2 particles is removed through a water-based process (hydrolysis). Finally, the pure TiO2 undergoes various surface treatments, milling, and drying to achieve the desired final product.

Waste Management: The chloride process generates waste products including unreacted coke and ore solids, as well as an acidic solution containing iron chloride (iron chloride waste acid).  These metal chloride impurities can be harmful to the environment.  Typically, they are neutralized with lime or limestone and then landfilled.  In rare cases, some facilities may inject these waste salts into deep wells.

Chlorine Consumption: The amount of chlorine consumed in this process is directly tied to the iron oxide content in the raw material.  More iron oxide requires more chlorine for conversion, with a portion being lost as hydrochloric acid during the process.

Reaction:

2TiO2 + 3C + 4Cl2 → 2TiCl4 + 2CO + CO2

TiCl4 (impure gas) → TiCl4 (pure liquit)

TiCl4 + O2 ➞ TiO2 + 2 Cl2

Sulfate Process

The sulphate process stands as the pioneering technology for producing Titanium Dioxide pigment commercially. In this method, ilmenite (containing 40% – 60% TiO2), titanium slag (with 72% – 85% TiO2), or a meticulously balanced mixture of both are treated with concentrated sulphuric acid (98%). The addition of carefully measured amounts of steam, water, and diluted sulphuric acid triggers a highly exothermic reaction. Lithopone, a white pigment consisting of a blend of barium sulfate (28% – 30%) and zinc sulfide (68% – 70%), alongside trace quantities of zinc oxide, is also produced through this process.

Reaction

FeTiO3 + 2H2SO4 → TiOSO4 + FeSO4 + H2O (Dissolution of the raw material)

TiOSO4 + H2O → TiO2n.H2O + H2SO4 (TiO2 precipitation)

TiO2n∙H2O → TiO2+ nH2O (TiO2 calcination and conditioning)

The resulting solution contains dissolved titanyl sulphate (TiOSO4) and iron sulphate (FeSO4) in sulphuric acid. If ilmenite is used as the feedstock, a reduction process is necessary to convert any ferric ions (Fe3+) to ferrous (Fe2+) ions, aiding in subsequent separation steps. To ensure complete iron dissolution, the solution is passed through scrap metal in an iron reduction step before clarification in a tank, allowing undissolved ore and solids to settle. The titanium solution is then concentrated and hydrolyzed to precipitate Titanium Dioxide hydrated. Filtration separates the hydrated Titanium Dioxide from ferrous sulphate and sulphuric acid. Iron sulphate is separated from the Titanium Dioxide production liquors through concentration and cooling. The hydrated Titanium Dioxide slurry undergoes calcination to grow crystals to their final size, removing residual water and H2SO4. The dried Titanium Dioxide proceeds to finishing, involving milling and potential chemical treatments like surface coating with silica or alumina. This finishing process, similar to the chloride method, includes coating, milling, and drying operations.

Major Applications of Titanium Dioxide

1. Cosmetics & Personal Care

In cosmetics, pigment-grade Titanium Dioxide is employed to conceal blemishes and enhance skin brightness. Its inclusion enables the application of thinner layers of makeup, achieving the desired effect with greater efficiency.

1. Pulp & Paper

Titanium Dioxide finds extensive use in coating paper, where its properties enhance its appearance and functionality. By incorporating Titanium Dioxide into paper coatings, manufacturers achieve a whiter, brighter, and more opaque finish. This not only enhances the visual appeal of the paper but also improves its overall quality. The Titanium Dioxide particles scatter light effectively, resulting in increased brightness and opacity. Additionally, the coating process allows for smoother printing and better ink adhesion, ensuring high-quality graphics and text. Overall, Titanium Dioxide plays a crucial role in enhancing the aesthetics and performance of paper products across various industries.

1. Paints & Coatings

Titanium Dioxide offers a dual benefit in paints, providing both opacity and durability. Its presence ensures that the paint effectively conceals underlying surfaces, imparting a solid, uniform appearance. Moreover, Titanium Dioxide enhances the paint’s resistance to environmental factors such as UV radiation, moisture, and abrasion, thereby extending the lifespan of the painted surface. By shielding against degradation and wear, Titanium Dioxide contributes significantly to the longevity of painted structures and surfaces. This combination of opacity and durability makes Titanium Dioxide an indispensable ingredient in paint formulations, ensuring not only aesthetic appeal but also long-lasting protection for various applications.

1. Plastics & Rubber

Titanium Dioxide plays a crucial role in mitigating the adverse effects of light exposure on plastics and other materials. By incorporating Titanium Dioxide into their composition, manufacturers can effectively minimize brittleness, fading, and cracking caused by prolonged exposure to light. The presence of Titanium Dioxide acts as a shield, absorbing and scattering harmful UV radiation, thus reducing the degradation of the material. This protective mechanism helps preserve the structural integrity and aesthetic appearance of plastic products, prolonging their lifespan and ensuring their durability in various applications.

Market Outlook

The future growth of the Titanium Dioxide market is expected to be largely driven by the increasing demand for paints and coatings. This is because Titanium Dioxide makes paints brighter by scattering light. It also improves their hiding power (opacity) and gives them a nice shine.  In fact, paints and coatings used about 40% of all Titanium Dioxide globally in 2023, and this number is expected to keep climbing.  The growing need for paints and pigments in various industries, including construction, personal care, and pharmaceuticals, is another factor that will likely boost demand for Titanium Dioxide. The global Titanium Dioxide market and is expected to grow at a CAGR of 5.08% by the year 2034.

Titanium Dioxide Main Players

Major players in the Global Titanium Dioxide market are The Chemours Company, Tronox Holdings Plc, Lomon Billions Group, Venator Materials Plc, KRONOS, The Louisiana Pigment Company, LP (KRONOS-Huntsman/Tioxide JV), The Kerala Minerals & Metals Limited, Indian Rare Earths Limited (IREL), and Cochin Minerals & Rutile Ltd (CMRL), and Others.

Conclusion:

In conclusion, Titanium Dioxide (TiO2) is a versatile and valuable material with a wide range of applications beyond its well-known use as a white pigment in paints and coatings. Its light-scattering properties make it ideal for sunscreens and cosmetics, while its photocatalytic abilities offer eco-friendly solutions for pollution reduction and energy saving. From everyday products like toothpaste and food coloring to advanced applications in construction materials, TiO2 plays a significant role in our daily lives and contributes positively to both the economy and environmental well-being. Fueled by rapid urbanization, the demand for paints, coatings, and pigments is likely to rise. As a result, this surge is expected to propel the global Titanium Dioxide market forward, as its exceptional light-scattering properties (high refractive index) make it the go-to white pigment for paint and coating production.