Study on Preparation and Coagulation Properties of Polyferric Sulfate and Polyacrylamide Composite Flocculants

The paper adopts the chemical speciation method of direct oxidation to prepare polyferric sulfate (PFS), taking the ferrous sulfate(FeSO₄·7H₂O) as the raw material, and then compounds PFS with a certain quantity of polyacrylamide (PAM) to produce a stable homogeneous phase composite flocculent, polyferric sulfate - Polyacrylamide (PFS-PAM). In addition, the paper employs Kaolin clay suspension as the simulated sample to explore the optimum flocculation conditions of the mixtures, and compares flocculating effects of PFS-PAM with that using PFS, PAM, and PFSS alone. Among them, the parameters such as PFS/PAM mass ratio, amounts of composite flocculants, acidity, reaction temperature, settling time for turbidity elimination rate were evaluated. The results show that under conditions of PFS/PAM mass ratio for 44, pH value for 6.0~8.0, amounts of PFS-PAM 2.5mg/L, reaction temperature for 40°C, and settling time for 40 min, the turbidity elimination rate of PFS-PAM on Kaolin clay suspension could reach around 75%, while the turbidity elimination rate on oily wastewater even could reach up to 96%, which is much better than that achieved by using the single coagulant.