Mechanistic insights into de-inking

Abstract

Mechanistic parallels between de-inking and laundering are complicated by the greater role of mechanical forces in de-inking processes. However, laboratory experiments indicate that ink removal from ledger paper, newspaper and a newspaper/magazine mixture is related to the de-inking surfactant cloud point — a clear parallel with detergency. This suggests there are similarities in the mechanisms of ink and soil detachment from fibers. Both the rollback mechanism and emulsification probably occur in the removal of liquid inks from cellulose fibers. The importance of solubilization in detaching ink from cellulose is less clear. This mechanism may compete with ink detachment promoted by the mechanical disaggregation of fibers. The softening of solid inks facilitates the detachment from cellulose by hydrodynamic forces. This process may well dominate the surfactant-promoted wetting and adsorption effects thought to operate in solid soil removal from cloth. Ink softening promotes the agglomeration of dispersed ink particles when they collide.