Abstract:

Polysilicicferric (PSF) coagulant with various Si／Fe ratios(PSF 0.5and PSF 3 represent Si／Fe molar ratios of 0.5 and 3, respectively), was prepared by co-polymerization. The alkalization experiments of PSF and coagulation performance of PSF in treating surface water collected from the Songhua River and sewagewater from Nangang district in Harbin  were investigated. The results showed that some informationassisted  the reaction mechanism between Si and Fe and the species transformation could be captured by the  alkalization experiment.The alkalization experiment further improved validation of  the SiFe reaction mechanism: much larger morphology based on Si-O-Fe-O-Fe-O-Si bond was immediately formed and then the unstable Fe-O-Fe bond breaks with increasing of thecopolymerization time in lower ratios of PSF (such as PSF 0.5) at initial copolymerization stage. While for higher ratios of PSF (such as PSF 3), only a small amount of Fe3+ participates in complexation with PS at the initial copolymerization stage, and species based on the SiOFeOSiOSi bond was formed. The optimum doses of PSF 05and PSF 3 are 85mg／L and 105mg／L for surfaces water and are 70mg／L and100mg／L for sewage water according to the removal of turbidity, UV254 an

d COD, respectively. PSF 3 gave a lower restabilization dose for turbidity rem

oval than PSF 05, while the contrary was true for UV254 and COD removal.

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Key words: Si, Fe, alkalization, coagulation