Synthesis, characterization and coagulation behavior of a composite coagulation reagent by the combination of polyferric sulfate (PFS) and cationic polyelectrolyte

Abstract

Latest developments on the synthesis of novel coagulants have reported the formation of reagents constituting of both inorganic and organic materials. In this study, the preparation of new composite reagents was achieved, by combining the inorganic pre-polymerized iron-based polyferric sulfate (PFS) with the cationic polyelectrolyte (CP) poly-dimethyl-diallyl-ammonium chloride (PDMDAAC) under different CP/Fe weight ratio. The reagents were prepared by using two different methods: co-polymerization and composite polymerization. Moreover, they were characterized in terms of typical properties, stability and morphological analysis (XRD, FTIR, SEM). Their coagulation performance was evaluating by treating low and high turbid (kaolin–humic acid) suspensions, while the usage of the Photometric Dispersion Analysis (PDA) apparatus enabled the investigation of the applied coagulation mechanisms. The results show that the new coagulants present improved coagulation properties, including an excellent stability. Coagulation experiments reveal that the PFS–CP composite reagent exhibits a superior coagulation performance, when compared to conventional coagulants. PDA analysis shows that the improvement of kinetic parameters with increasing CP/Fe ratio (especially in comparison with PFS) is attributed to the nature and properties of the cationic polymer.