Separation of Contaminants from Deinking Process Water by Dissolved Air Flotation: Effect of Flocculant Charge Density

Abstract

The effect of charge density of 5 cationic polyacrylamides (C-PAMs)and 3 anionic polyacrylamides (A-PAMs) in single and in dual treatments with a coagulant on the flocculation and removal of dissolved and colloidal material by dissolved air flotation (DAF) in papermaking has been studied. In single systems, good results were achieved both with low and high charge C-PAMs(1.0and 3.0–3.5 meq/g). In dual sy tems, high charge C-PAMs (3.0–3.5 meq/g)and A-PAMs (1.5 meq/g), were the most efficient. Results show that monitoring flocculation by a focused beam reflectance measurement (FBRM) allows paermakers to optimize the chemical dosages to maximize the separation efficiency of DAF units either with single or dual systems, which is not always possible with traditional methods as charge titration.