Abstract
Abstract The flocculation of a specially prepared sol of kraft lignin by polyethylene oxide (PEO) was studied. The effects of polymer dosage, sol concentration, pH, and electrolyte addition (NaCl and CaCl2) on the flocculation behavior were investigated. The efficiency of lignin removal increased with increasing electrolyte concentration, valency of the counterion, and decreasing pH of the sol. In all cases maximum flocculation occurred at an optimum polymer dosage (O.P.D.) which was found to be independent of pH and electrolyte concentration within the intervals studied. The O.P.D. (as percentage of the sol concentration) was found to be independent of the sol concentration. The mechanism of restabilization was studied by heating the stable dispersions to temperatures exceeding the θ-temperature of the PEO. The critical flocculation temperature was found to coincide with the θ-temperature of the PEO (enthalpic stabilization). The mechanism of flocculation is discussed and it is concluded that bridging oc...
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