The effect of pH on pulping and flotation of mixed office wastepaper

The effect of pulping reagents on the deinking flotation of laser-printed w astepaper was investigated with regard to the removal efficiency of toner a nd mineral filler particles at different pH values. These results show that caustic pulping causes the toner to be released from the fibres as larger particles and a poor floatation response is obtained On the other hand, neu tral pulping not only causes the toner to be released as smaller particles but also increases the simultaneous floatation removal oftener and mineral filler particles. On the basis of these flotation results and atomic force microscopy force experiments, it is known that the remarkable removal of mi neral fillers and toner particles under acidic conditions is related to the heterocoagulation oftener and filler particles.