Speciation characterization and coagulation of poly-silica-ferric-chloride：The role of hydrolyzed Fe（Ⅲ） and silica interaction

Speciation characterization and coagulation of poly-silica-ferric-chloride: Therole of hydrolyzed Fe(III) and silica interaction

The highly e cient inorganic polymer flocculants (IPFs) of the ferric-silica system is a new and promising coagulant. Interactionsbetween ferric species and silica play a large part in the coagulation of suspensions. These e ects are quite distinct from those associatedwith polymeric or colloid silica. However, although these species are key to coagulation e ciency, they have not been comprehensivelydiscussed. A new type of coagulant, poly-silica-ferric-chloride (PFSC), was synthesized by co-polymerization and characterized bytime complexation spectroscopy and photon correlation spectroscopy. Compared with traditional ferric salt, the results indicated thatPFSC had a higher molecular weight, lesser positive charge, lower Feb and higher Fec. The higher the Si/Fe ratio, the higher the silicaand lower the silicac found. The PFSC with appropriate polysilica acid not only obtained better coagulation/flocculation e ciency inturbidity removal, enhanced the flocculation index (FI) and provided less residual ferric, it also lowered water treatment costs comparedto traditional ferric salt. Results showed that PFSC could remove colloid particles in water by charge neutralization and sweeping,adsorption bridging mechanism.