Impacts of key preparation factors on polymerization and flocculation performance of polyferric silicate sulfate (PFSiS)

Polyferric silicate sulfate (PFSiS) was prepared by copolymerization of polysilicic acid (PSi) and Fe 2 (SO 4 ) 3 , and the impacts of the key preparation factors, the ratio of Si/Fe (R Si/Fe ) and the pre-aging time of PSi (T), on the polymerization and flocculation performances of PFSiS were explored in this work. PFSiS with different R Si/Fe and different T were prepared, and the physicochemical properties and flocculation performance of PFSiS on hydrophobic dye (Disperse yellow), anionic hydrophilic dye (reactive turquoise blue) and cationic hydrophilic dye (methylene blue) were compared. The crystal structure and chemical bond of PFSiS were characterized by XRD and FTIR, respectively. The molecular dynamics simulation was used to compare the molecular structures of PFS and PFSiS formed by PSi with different polymerization degree. The results show that the R Si/Fe and T can impact the polymerization degree of PSi. When the R Si/Fe and T is small, there are a lot of (OH) 3 SiO - neutralize with positively charged Fe-polymer during copolymerization, which reduces the neutralization ability of PFSiS, resulting in a worse flocculation performance on RTB. This situation does not affect the improvement of the flocculation performance on DY due to the strengthening of adsorption bridging capacity. With the increase of the R Si/Fe and T, the improvement of the PSi polymerization degree produces long chains of Si-polymer bonded with positively charged Fe-polymer in PFSiS, which has both electric neutralization and excellent adsorption bridging capacity and makes its flocculation performance on three kinds of dye wastewaters better. High R Si/Fe and T influence the neutralization ability and the viscosity of PFSiS and reduce the flocculation performance on DY and RTB. At the same dose, the decolorization rate of PFSiS on DY is 54% higher than that of PFS, but there is little difference on RTB. PFSiS also maintains the part flocculation ability of PSi on MB, but it is affected by positively charged Fe-polymer.