What is zinc sulfate?

Zinc sulfate is an inorganic white substance with the chemical formula of ZnSO₄.nH₂O. This compound is one of the most widely used zinc salts, with various applications in industry and agriculture.

Zinc sulfate is soluble in water and in the presence of lime or carbonate compounds in the soil, it is precipitated as carbonate salt which is insoluble in water.

The heptahydrate zinc sulfate has crystalline form and the anhydrous form is white powder. If it is contaminated with cadmium, its color turns to light yellow, which leads to low-quality product with lower price. Also, zinc sulfate may be contaminated with heavy elements such as lead, cadmium, arsenic and nickel, the main reason being that these elements are associated with zinc mineral ore, so it is not suitable to use as fertilizer in agriculture and causes soil and plant contamination.

Zinc sulfate production method

The industrial method for zinc sulfate production is the reaction between diluted sulfuric acid and zinc oxide mineral soil, or zinc smelter slag, or zinc oxides. However, it should be noted that most zinc slag contains large amounts of chlorine due to the use of ammonium chloride, and the produced zinc sulfate using zinc slag contains excessive amounts of chlorine that is harmful for plants. The solution obtained from the reaction of soil or zinc concentrate with sulfuric acid, contains lead, cadmium, nickel, manganese, and cobalt.

Lead sulfate is precipitated due to its very low solubility product constant, Ksp, and is separated by a press filter. To separate cobalt and manganese, these ions can be converted to higher oxidation states by the use of strong oxidants such as potassium permanganate or ozone gas injection. Then by increasing the pH of the solution with adding calcium carbonate or hydrated lime, manganese, and cobalt are deposited and separated from the zinc solution. This reaction takes place at high temperature and is called heat treating. The resulting cake contains cobalt and manganese oxides and is called cobalt cake or hot cake. Cadmium and nickel ions are also separated from solution by reduction and cementation to metal cadmium and nickel by adding zinc powder to the solution. This reaction takes place at low temperatures and is called cold treating, and the resulting filter cake is called as cold cake or nickel cake.

How to dissolve zinc sulfide (sphalerite) soil in sulfuric acid

Zinc sulfide soil or concentrate, does not dissolve directly in sulfuric acid. It can be dissolved in high pressure  (8-10 bar) vessels, in the presence of oxygen gas.

Very pure zinc sulfate is produced by the reaction of sulfuric acid with zinc oxide or zinc carbonate and then cooling of the solution and crystallization. This substance is used for medical and pharmaceutical purpose.

Applications and uses of zinc sulfate

• As fertilizer in agriculture to supply zinc for wheat, pistachios, grapes, and citrus
• Manufacture of synthetic silk and zincolith
  
• Used in livestock and poultry concentrate
• Production of electrolytes
• Production of zinc phosphates
• Production and manufacturing of degreasers and paint stripper

Hamun industrial group, one of the main producers of zinc ingots and zinc sulfate in Iran, is ready to supply and sell zinc sulfate to domestic and foreign farmers and industrialists all around the world.

• Zinc grade : 33%
• Seeding: Dry powder produced by Dreyer spray
• Packaging: 25 kg bags or 500 to 1000 kg jumbo bags