Flocculation kinetics and floc characteristics of dye wastewater by polyferric chloride-poly-epichlorohydrin-dimethylamine composite flocculant

The polyferric chloride-poly-epichlorohydrin-dimethylamine (PFC-ECH-DAM) composite flocculants with different OH/Fe ratios, Fe to organic ECH-DAM mass ratios and cross-linker types were comparatively investigated in terms of formed floc aggregation process and floc characteristics for the treatment of synthetic dyeing wastewater. The effect of OH/Fe molar ratio (B value), Fe to ECH-DAM mass ratio (MR value), cross-linker type and ECH-DAM addition on floc characteristics was investigated as function of flocculant dosage and dye wastewater pH. The results demonstrate that the synergic effect of PFC with ECH-DAM promoted the formation of larger flocs with higher growth rate and wider distribution of floc sizes. During the coagulation of reactive red (K-2BP) dyeing wastewater, strengthened floc properties can be obtained at higher flocculant dosage ranges (>80 mg/L) and solution pH of about 7.5. The floc TWV values appear to show that the predominant flocculation mechanism of PFC-ECH-DAM are bridging adsorption and sweep flocculation. In addition, relatively lower OH/Fe molar ratio, higher Fe to ECH-DAM mass ratio and utilizing polyethylene polyamine as cross-linker were favorable for the formation of flocs with larger size, higher growth rate and larger size variation. (C) 2013 Elsevier B.V. All rights reserved.