The use of cationic surfactants to enhance the deinking of coated fine papers

A deinking process is based on two fundamental operations: defibering and deinking. Defibering depends on added chemicals and shear stress applied to a wastepaper suspension. The defibering operation and the added chemicals control ink removal. In this study disintegration stock concentration, rotor speed and disintegration time are used to optimise defibering to a Somerville index less than 0.01%. Higher stock concentrations always represent minimum specific energy consumption (SEC) due to shear and acceleration effects. The effect of cationic surfactant and addition points of chemicals are evaluated. When cationic surfactant is used to enhance ink removal the best performance is achieved with disintegration at basic pH and flotation at neutral pH. The addition of cationic surfactant in the flotation step is beneficial as it minimises ink dispersion.