Klordioxid

Klordioxid, or chlorine dioxide (chemical formula ClO2), is an inorganic compound consisting of a chlorine atom bonded to two oxygen atoms. It is typically encountered as a yellow to reddish-yellow gas at room temperature and is soluble in water, where it forms weakly acidic species such as chlorous acid. The molecule is a radical with an odd number of electrons, which gives it distinctive reactivity and paramagnetism.

ClO2 is a strong, selective oxidizer. It reacts readily with a wide range of substrates, including organic matter, metals, and inorganic compounds. In water treatment and pulp bleaching, its oxidizing action is valued for its ability to break down impurities while forming fewer chlorinated byproducts compared with chlorine. However, in aqueous solutions it can disproportionate, forming chlorite (ClO2−) and chlorate (ClO3−) species as byproducts, and it decomposes under heat, light, or in contact with reducing agents.

Industrial production of chlorine dioxide typically involves the controlled, partial reduction of sodium chlorate in acidic solution, using reducing agents to release ClO2 gas, which can then be captured or dissolved. Handling requires careful controls because ClO2 is a reactive oxidizer that can pose fire and explosion risks at high concentrations and dry conditions.

Common applications include pulp and paper bleaching, drinking-water and sanitizing processes, and odor control. Safety concerns center on inhalation exposure, irritation of skin and eyes, and the potential formation of chlorite and chlorate in treated water. Environmental fate generally leads to oxidation products such as chlorite and chlorate, rather than persistent accumulation.