Heteroagglomeration as a mechanism of retaining CaCO3 particles on the fibrils of cellulosic fines: A study by laser light diffraction and microscopy

Mutual agglomeration involving contrasting types of particles can be expected to play a major role during the formation of paper. The present work employed laser diffraction particle size analysis, as well as microscopy, to characterize the state of agglomeration between cellulosic fines and precipitated calcium carbonate (PCC) particles. Primary fines from bleached hardwood kraft pulp were compared with fines collected from the same pulp after mechanical refining. Various ratios of cellulose to PCC were studied. Results were consistent with a process of heteroagglomeration occurring mainly between the PCC and slender cellulosic fibrils associated with the cellulosic fine particles. Adhesive attachments were formed between the PCC and cellulosic surfaces in spite of their having the same sign of zeta potential.