General Discussion

Sodium chlorate (NaClO₃) is a powerful inorganic oxidizing agent produced on an industrial scale primarily for the manufacture of chlorine dioxide, a key bleaching agent in the pulp and paper industry. It is manufactured through the electrolysis of a hot, saturated sodium chloride brine in large, undivided cells. This electrochemical process involves the anodic oxidation of chloride ions to form chlorate, with simultaneous hydrogen evolution at the cathode. The resulting solution is then crystallized to yield white, crystalline NaClO₃. It is a strong oxidizer, meaning it readily donates oxygen to support combustion of flammable materials; as such, it is classified as a hazardous material that requires careful handling and storage, separate from organic compounds, acids, and reducing agents to prevent fire or explosion.

The dominant global application for sodium chlorate, accounting for over 90% of production, is as the on-site precursor for chlorine dioxide (ClO₂) generation in pulp mills. Chlorine dioxide, produced by reducing sodium chlorate with a reducing agent like methanol or hydrogen peroxide in an acidic medium, has become the standard for environmentally preferable elemental chlorine-free (ECF) bleaching, as it produces fewer toxic dioxins. Beyond pulping, sodium chlorate is used as a non-selective herbicide and defoliant, most infamously in the formulation of "Agent Green" during the Vietnam War. It also finds use in smaller-scale applications such as uranium ore processing, in the production of other chlorates and perchlorates (like potassium chlorate for matches and pyrotechnics), and as an oxidizing agent in some chemical synthesis processes. Its production and use are tightly linked to the pulp industry's environmental practices and regulations.