What Is Lead Sulfate?
Lead sulfate is an inorganic compound consisting of lead sulfate and lead ions combined with the chemical formula PbSO4.
It has a mass of 303.26 g/mol, a density of 6.29 g/cm3, and a density of 1170°C. At normal temperature and pressure, it has the appearance of a white solid.
Uses of Lead Sulfate
1. Lead-acid batteries
Lead sulfate is used as a cathode and anode active material for the electrodes of lead-acid batteries. The relatively low cost of lead as an electrode material makes it possible to manufacture storage batteries with high-cost performance. Lead dioxide is used as the electrode for the positive electrode and lead for the negative electrode, and lead sulfate has been used as the electrolyte for both.
Dilute sulfuric acid is ionized by water to SO₄²- and H⁺, which reacts with sulfate ions to form lead sulfate, PbSO₄, at the negative electrode. Lead sulfate adheres to the surface of the anode in solid form, and the mass of the anode increases rapidly. In addition, electrons generated by the oxidation of lead are transferred to the cathode through conductors.
In addition, hydrogen ions are also released into the electrolyte, and the hydrogen ions are directed to the cathode, where free electrons have gathered, and move through the electrolyte, which is the principle of the battery. The cathode plate, on the other hand, accepts the free electrons and hydrogen ions from the anode and undergoes a chemical reaction with lead dioxide and dilute sulfate. As a result, lead Sulfate and water are formed, and the lead sulfate adheres to the cathode plate in the same manner as the anode plate.
The lead sulfate and other substances adhering to the surface of the cathode plates due to discharge cause a recharging reaction that returns the battery to the state it was in before discharge, allowing it to be used repeatedly. The positive electrode is oxidized to lead oxide (IV) by recharging, and the negative electrode is reduced to solid lead, which is a property of lead-acid batteries.
2. Pigment
Lead sulfate has been used as a white pigment in various situations since ancient times because of its white color. Lead sulfate has also been found in the treasures of the Shosoin Repository in Nara, Japan.
Lead sulfate is also characterized by its use as one of the raw materials for coloring pigments such as yellow lead and molybdate orange. However, in recent years, there has been a growing movement toward the elimination of lead-containing paints due to concerns about the adverse effects of lead-containing paints on the human body.
3. Other
Other applications include glazes, catalysts, and resin stabilizers.
Properties of Lead Sulfate
1. Physical Properties
It is a white or colorless, crystalline or crystalline powder solid in appearance. It is soluble in excess alkali hydroxide as lead hydroxide ions, but its solubility in water is almost negligible at 0.0425g/1L at 25℃. It is also insoluble in organic solvents such as ethanol and acetone.
The crystal structure is stable with a barium sulfate-type structure and a rectangular crystal structure. Its melting point is 1,170°C, but decomposition begins at around 1,000°C. It decomposes to lead(II) oxide or lead(III) tetroxide while generating sulfur dioxide and sulfur trioxide.
2. Lead Sulfate Manufacturing Process
Lead sulfate is produced by the reaction of a water-soluble lead compound with a strong acid, such as lead sulfate and lead nitrate, or lead sulfate and lead acetate, accompanied by heating. Lead sulfate is obtained as a white precipitate.
In addition, a paste made by adding dilute sulfate to lead(II) oxide is used as the active material in lead-acid batteries, which contains various basic salts with compositions such as PbSO4·PbO、PbSO4·2PbO、PbSO4·3PbO、PbSO4·4PbO. In addition, water is a byproduct of this reaction.
When lead sulfate reacts with lead, lead sulfate and hydrogen are formed, but a film of insoluble salts is formed on the surface of the reactants, which must be heated to facilitate the reaction.
Other Information on Lead Sulfate
Hazards of Lead Sulfate
Lead sulfate is highly toxic and may cause cancer, harm the fetus in pregnant women, and damage the organs (kidneys, nervous system, digestive system, and blood system). Therefore, it is necessary to wash hands thoroughly and wear rubber gloves, lab coats, masks, and protective goggles when handling it.
In addition, because of its harmful effects on aquatic organisms, its release into the water is strictly regulated.