Effect of PEO molecular weight on the flocculation and resultant floc properties of polymer-induced PCC flocs

The tensile strength of precipitated calcium carbonate flocs, formed with the poly(ethylene oxide) (PEO) cofactor flocculation system, was measured as a function of PEO molecular weight together with two types of cofactor, a commercial sulphone containing phenolic resin and a linear copolymer of vinyl phenol and sodium acrylate. The floc tensile strength ranged from 10 to 130 nN when PEO molecular weight was increased from 2 to 8 million Dalton. The two types of cofactors gave approximately the same range of tensile strengths, however, the elongation at break was about 800% for the vinyl phenol-based cofactor whereas the commercial cofactor gave only about 300% elongation. It was postulated that elongation is an important predictor of floc survivability in turbulent flow.