A method of enhancing the recovery of useful coal or potassium chloride or borax from screenbowl centrifuge separation operations comprising adding to the screenbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said cationic terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent of one or more nonionic monomers.