delignify

Delignify is a verb meaning to remove lignin from plant material, especially wood. Lignin is a complex aromatic polymer that binds cellulose fibers, contributing to rigidity and resistance to decay. Delignification is a core step in pulp and paper production, where cellulose fibers must be freed from lignin to form usable pulp.

Industrial methods include chemical pulping (kraft and sulfite processes) which use alkaline or acidic conditions to break lignin bonds and solubilize it; wood chips are cooked to reduce lignin content. Organosolv pulping employs organic solvents to dissolve lignin. Biological approaches use ligninolytic enzymes, or white-rot fungi, to degrade lignin, sometimes as pretreatment to improve enzymatic hydrolysis of biomass.

Applications: delignified cellulose is essential for papermaking and for producing textile fibers like viscose and lyocell after bleaching; it also improves access to carbohydrates in lignocellulosic biomass for biofuels and biochemicals. Lignin removal is often balanced because lignin can contribute to fiber strength and to certain paper properties; over-delignification can weaken the material.

Environmental and analytical considerations: the degree of delignification is tracked by lignin content and the kappa number; pulping produces spent liquor containing sulfur compounds, organic solvents, or degraded lignin derivatives, raising environmental concerns; mills use chemical recovery and green processing strategies to mitigate impacts.

History: advances in chemical pulping in the 19th and 20th centuries enabled modern paper production.