causticized

Causticized is a term used to describe a substance that has undergone a process of causticization. This process typically involves treating a material, often a plant-based substance like wood or straw, with a caustic alkali, most commonly sodium hydroxide (caustic soda) or potassium hydroxide. The purpose of causticization is to break down the complex structure of the material, particularly its cellulose and hemicellulose components. This breakdown solubilizes certain components and alters the physical properties of the material, making it more amenable to further processing.

In the context of papermaking, causticization is a crucial step in the alkaline pulping process, such as the Kraft process. Here, wood chips are treated with a mixture of sodium hydroxide and sodium sulfide, known as white liquor. This alkaline solution breaks the lignin bonds that hold the wood fibers together, separating the cellulose fibers to form pulp. The spent liquor, now containing dissolved lignin and other wood components, is then processed to regenerate the sodium hydroxide and sodium sulfide, a recovery process also referred to as causticizing.

Beyond papermaking, causticization can be applied to other organic materials for various purposes. For instance, it can be used in the production of certain types of animal feed by increasing digestibility, or in the modification of agricultural residues for biofuel production. The term implies a chemical alteration caused by the action of a strong alkali, leading to changes in solubility, structure, and reactivity.