Preparation and Characterization of a Composite Coagulant: Polyferric Titanium Sulfate

In this study, a novel composite coagulant polyferric titanium sulfate (PFTS) was synthesized and the kaolin-fulvic acid simulated water was employed to verify the coagulation efficiency. To obtain the optimal conditions for preparing the composite coagulant, the parameters affecting the coagulation performance such as Ti/Fe, P/Fe, OH/Fe, and oxidizer dosage were evaluated by single factor experiments and response surface methodology. The structure and morphology of PFTS were investigated by some conventional methods and those affecting coagulation–flocculation behaviors such as coagulant dosage, water sample initial pH, were also examined. Flocs properties of PFTS were investigated by Mastersizer 2000. The results indicated that PFTS presented a porous and a compacted gel network structure, in which some major phase structure and chemical bonds were discovered. The jar tests demonstrated the superior coagulation performance at coagulant dosage of 20–30 mg/L and the optimum pH range of 7–8. The optimum synthetic conditions were Ti/Fe, P/Fe, OH/Fe molar ratio and oxidant adding speed of 0.13, 0.25, 0.29, and 4 mL/min, respectively. Under the optimal condition, the residual turbidity, (Dissolved organic matter) DOC removal and residual iron of 0.82, 53 %, and 0.08 mg/L, respectively, could be acquired by PFTS. The flocs analysis results manifested that the dominant mechanism in flocs growth is absorption-bridging and sweeping coagulation, while charge neutralization mechanisms is the primary in the formation of compact flocs.