3 Alkaline Decomposition Methods for Preparation of Zirconium Sulfate

Zirconium and sulfuric acid can produce a variety of compounds, the most common ones being acidic zirconium sulfate and basic zirconium sulfate. Acidic zirconium sulfate, also known as zirconyl sulfuric acid, is widely used in industry, and its molecular formula is H2[ZrO(SO4)2]•3H2O or Zr(SO4)2•4H2O. The tetrahydrate of zirconium sulfate appears as hexagonal plate crystals, while the anhydrous form is a white powder. It is a main intermediate product of zirconium and can be used as a white leather tanning agent. The preparation of zirconium sulfate from zircon involves three steps: alkali decomposition, preparation of zirconium sulfate solution, and precipitation of acidic zirconium sulfate. This article focuses on explaining these three methods of alkali decomposition. Currently, there are three methods of alkali decomposition, namely the sodium hydroxide melting method, the sodium carbonate sintering method, and the lime sintering method.

Zirconium(IV) sulfate - Wikipedia

Sodium Hydroxide Fusion Method

The sodium hydroxide fusion method, also known as the alkali fusion method, involves adding zircon and sodium hydroxide to the reaction tank in a 1:1.3 ratio and reacting them at a temperature of 923-973K to form Na2ZrO3. The main reaction formula is ZrSO4+4NaOH=Na2ZrO3+Na2SiO3+2H2O, and the decomposition rate of zircon can reach about 99%. The alkali fusing material is then washed with water to remove soluble impurities such as excess alkali and sodium silicate. The resulting filter cake is sent for leaching to obtain a zirconium sulfate solution. The washing materials include sodium zirconate, sodium zirconium silicate, hydrated zirconia, and sodium titanate. The main features of this method are the low reaction temperature and the high decomposition rate of zirconium.

Sodium Carbonate Sintering Method.

Sodium carbonate sintering method, also known as the direct sintering method, involves putting zircon and sodium carbonate in a pan-type ball forming machine in a molar ratio of 1:3 to create pellets. The mixture is then sintered in a rotary kiln at 1373K, and the main reaction that takes place is:


After the firing process, the material is crushed and washed with water to eliminate soluble impurities such as sodium silicate. The resulting mixture is then filtered to obtain a filter cake, mainly comprising of sodium zirconate, which is later leached to produce a zirconium sulfate solution. Alternatively, zircon and sodium carbonate can be used in a molar ratio of 1:1.3. In this case, the primary sintering reaction is:


As observed from the reaction formula, the sintered product primarily consists of sodium silicon zirconate. The sintered product is then decomposed using sulfuric acid. During this process, zirconium produces zirconium sulfate and enters the solution, while silicon forms silicic acid, which can be effectively polymerized and removed during filtration. Although this method saves a significant amount of sodium carbonate, it consumes a considerable amount of acid and requires high reaction temperatures. The decomposition rate of zircon is approximately 95%.

Lime Sintering Method

The lime sintering method involves adding zircon and limestone (or chalk) in a molar ratio of 1:3, with an excess of 10% to 20% limestone. Then, calcium chloride with a mineral content of 5% is added, mixed evenly, and sent into a rotary kiln at a temperature of 1373-1473K for 4-5 hours. The decomposition rate of zircon is about 97%-98%. After sintering, the material is first washed with a cold solution containing 5% to 10% HCl to remove excess CaO, CaCl2, and most of Ca2SiO4. The generated colloidal silicic acid is also removed together with the solution. The resulting calcium zirconate is then leached with a solution containing 25% to 30% HCI at a temperature of 358-363K. Alternatively, sulfuric acid can be used for leaching. The biggest advantage of this method is that the decomposition agent is cheap and easy to obtain, but it has the disadvantage of high decomposition temperature and low decomposition rate.


In summary, zirconium sulfate is an important industrial material produced through alkali decomposition of zircon. The three primary methods of alkali decomposition are the sodium hydroxide fusion method, sodium carbonate sintering method, and lime sintering method. Each method has its advantages and disadvantages in terms of decomposition rate, reaction temperature, and cost of decomposition agents. Ultimately, the choice of method depends on the specific requirements of the production process.

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10 Common Zirconium Products and Their Applications

1. Zirconium Silicate

Zirconium silicate is an important variety in traditional zirconium products. The product is made of zircon sand, which can be obtained after grinding, calcining and powdering. It is a high-quality and cheap opacifying agent for ceramic glazes.

Zirconium silicate is mainly used for color glazes of architectural ceramics, daily-use ceramics and electric porcelain. It is also widely used in high-grade refractory materials, precision casting, emulsified glass and other industries.

2. Zirconium Carbonate

Zirconium carbonate is a source of zirconium that is insoluble in water but is easily transformed into other zirconium compounds. It is mainly used as an additive for cosmetics, waterproofing agent, flame retardant, opacifying agent, and surface aid for fibers and paper, and can also be used to prepare zirconium-cerium composite catalytic materials. It is an important raw material in the textile, papermaking, paint, and cosmetic industries, and its consumption has been increasing in recent years.

3. Zirconium Oxychloride

Zirconium oxychloride is the main raw material for the production of other zirconium products such as zirconium dioxide, zirconium carbonate, zirconium sulfate, composite zirconium oxide, and the separation of zirconium and hafnium to prepare metal zirconium and hafnium. In addition, it can be used in textiles, leather, rubber additives, metal surface treatment agents, paint drying agents, refractory materials, ceramics, catalysts, fire retardants, and other products. The primary source material for zirconium oxychloride is zircon sand.

4. Fused Zirconia

Fused zirconia is mainly used in the production of glazes and refractory materials. Due to the high content of impurities in fused zirconium, its use is sometimes limited.

5. Zirconium Sulfate

Zirconium sulfate is an intermediate raw material for the production of zirconium chemicals and metal zirconium and hafnium. It is also an important raw material for the production of leather tanning agents, wool treatment agents and paint surface oxidants. Additionally, it can be used as a catalyst carrier, amino acid and protein, precipitant and deodorant.

Consumption Structure of Zirconium Products
Consumption Structure of Zirconium Products

6. Zirconium Dioxide

Zirconium dioxide, or zirconia, is a non-toxic, odorless white solid. It has sufficient stability in alkaline solutions and many acidic solutions. ZrO2 ceramic is suitable for precision ceramics, electronic ceramics, optical lenses, glass additives, electrolytic zirconia bricks, ceramic pigments, enamel, artificial gemstones, refractory materials, grinding and polishing and other industries and products.

7. Composite Zirconia

Composite zirconia, referring to stabilized zirconia, is a non-toxic, odorless white powder. It has stable chemical properties and controllable specific surface area. It is the basic raw material for the manufacture of various special ceramics, advanced refractory materials, optical communication devices, and new energy materials.

8. Nuclear Grade Zirconium

Nuclear-grade zirconium is mainly used as the structural material of nuclear-powered aircraft carriers, nuclear submarines, and civil power reactors, and the cladding of uranium fuel elements. It is an important strategic metal.

9. Industrial Grade Zirconium

Industrial-grade zirconium is mainly used in the production of chemical acid and alkali-resistant equipment, the military industry, the electronics industry, pipeline valve materials, special high-strength, and high-temperature alloy materials, and getters for electric vacuum and lighting bulb industries.

10. Metallurgical Grade Zirconium

Metallurgical grade zirconium is used as a firearms sponge zirconium combustion agent and is also suitable for alloy additives and metallurgical deoxidizers, the chemical industry, civilian flash fireworks, etc.