Modified inorganic polymer flocculant-PFSi: its preparation, characterization and coagulation behavior

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment Technologies

Background:

• Inorganic polymer flocculants (IPFs) are emerging as advanced reagents for water and wastewater treatment.
• Iron-based IPFs are particularly desired due to their lack of toxicity.
• Tailoring the properties of polyferric silicate (PFSi) is crucial for optimizing its performance.

Purpose of the Study:

• To investigate a new protocol for preparing iron-based inorganic polymer flocculants (IPFs).
• To explore the effect of different silica modifiers (silicaA, silicaB, silicaC) on polyferric silicate (PFSi) properties.
• To analyze the species distribution and coagulation behavior of the synthesized PFSi variants.

Main Methods:

• Preparation of three distinct silica types (silicaA, silicaB, silicaC).
• Synthesis of polyferric silicate (PFSi) using these silica modifiers.
• Employing direct and indirect speciation methods to analyze iron species distribution.
• Examining the coagulation behavior of the prepared PFSi materials.

Main Results:

• The species distribution in PFSi is primarily determined by the type of silica used and the Si/Fe ratio.
• SilicaA and silicaB acted as precipitation inhibitors during Fe(III) hydrolysis, increasing monomers (Fe(a)) and decreasing colloidal species (Fe(c)) with increasing Si/Fe ratio.
• SilicaC showed minimal impact on the Fe(III) species distribution, and stabilization of oligomeric/polymeric species (Fe(b)) was not achieved under tested conditions.

Conclusions:

• The choice of silica modifier critically influences the speciation of iron in polyferric silicate.
• SilicaA and silicaB offer potential for controlling iron species, which could impact coagulation efficiency.
• Further research is needed to achieve stabilization of polymeric iron species for enhanced flocculant performance.