Influence of Si/FeO42− mol ratio on coagulation of poly-silicic-ferric coagulant from fly ash extract

Ploy-high-ferric-silicic coagulant from fly ash extract with various Si/FeO₄^2- mol ratios was prepared using potassium ferrate. The influence of Si/FeO₄^2- mol ratio on both structure morphology and influence mechanism of poly-high-ferric-silicic was investigated. The coagulation efficiency using poly-high-ferric-silicic as coagulant in treating lead wastewater in comparison with that using PFPS as coagulant was studied. The results show that the relative amount of Si or Fe in poly-high-ferric-silicic has a limit ratio. Poly-high-ferric-silicic can give the optimum complex action of Si and Fe only at the optimum Si/FeO₄^2- ratio range which is near the limit of Si/FeO₄^2- ratio. Color, turbidity and Pb²⁺ removal efficiency are excellent and treatment effects are stable in treatment lead wastewater, especially the removal of Pb²⁺ has been up to 96% more and the poly-high-ferric-silicic dosage is low. Therefore, by comparison, the poly-high-ferric-silicic is a superior coagulant in lead wastewater treatment.