Why Is FAS Used for Deinked Pulp (DIP) Bleaching?

“Deinked pulp brightness is often limited by residual chromophores rather than lignin. FAS provides reductive bleaching under alkaline conditions. Fibre yield loss is generally small when process conditions are controlled. Actual brightness gain depends on furnish, ink system, consistency, pH, temperature, reaction time, metal ions and FAS dosage.”