• Categories:Applications
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• Time of issue:2023-08-27
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(Summary description)At present, the annual production of titanium dioxide in the world exceeds 6 million tons, most of which is used in pigments. Due to its high refractive index, good optical stability and chemical inertness, titanium dioxide is widely used in paint, rubber and plastic, paper, cosmetics and other industrial fields. In addition to conventional pigment applications, titanium dioxide is also used in other industrial sectors such as energy, pharmaceuticals, environmental and electronic materials.

    There are two industrial methods for producing the pigment titanium dioxide: the sulfuric acid method and the chlorination method.

    The sulfuric acid process was the first method for the production of anatase and rutile titanium dioxide. In this method, concentrated sulfuric acid is used to dissolve ilmenite (FeTiO3, containing 40% to 65% TiO2), titanium slag (containing 75% to 85% TiO2), or a mixture of the two in a certain proportion. Through the separation of insoluble impurities, a sulfuric acid solution of titanium is obtained. Hydrated titanium dioxide precipitation is achieved by adding suitable seed crystals and heating and boiling. The resulting precipitate is filtered and washed to remove acids and soluble impurities. Hydrated titanium dioxide is calcined at high temperature to obtain the primary pigment titanium dioxide. The chlorination process requires the use of titanium ore that is purer than the sulfuric acid process. Titanium ore first reacts with Cl2 under carbonic conditions, and the obtained titanium tetrachloride is purified by distillation. Titanium tetrachloride is oxidized at high temperature to generate titanium dioxide. The untreated pigment titanium dioxide is dispersed in water by a ball mill or sander to ensure the elimination of excessively large particles consisting of sintered aggregates. Dispersants are often used to promote the dispersion of titanium dioxide in water.

    After that, the production process usually inorganic coating of titanium dioxide particles, and then washing, filtration, drying, gas powder and other processes to produce TiO2 products.

    The production of titanium dioxide essentially extracts TiO2 from low-purity ores, mainly ilmenite: FeOTiO2. While the main impurity of ilmenite is iron, other metal impurities also contain manganese, chromium, vanadium, zinc, copper, lead, nickel, and, to a lesser extent, cadmium and mercury.

    The two production methods of titanium dioxide are to extract titanium dioxide from ore with sulfuric acid or chlorine. The sulfuric acid process typically requires the use of more than 3 tons of acid to produce 1 ton of titanium dioxide. Historically, all these acid and metal impurities have been discharged into the water. Although most of the chlorine in the chloride process is circular, the reaction impurities are excreted as metal chlorides. Both production methods have a large amount of harmful gas production.

The generation and discharge of industrial wastewater has also attracted great attention. In the past few decades, the environmental problems in titanium dioxide production have undergone very positive changes, and the environmental concept of green production has been widely accepted in Europe and the United States and other countries.