Synthesis, characterization and flocculation activity of novel Fe(OH)3–polyacrylamide hybrid polymer

A novel Fe(OH)3–polyacrylamide inorganic–organic hybrid polymer (FHPAM) was synthesized via free radical solution polymerization initiated by a redox initiation system ((NH4)2S2O8–NaHSO3) in an aqueous medium. Reaction parameters influencing the intrinsic viscosity and the yield of the hybrid polymer, such as initiator concentration, monomer mass fraction, temperature and reaction time were investigated and optimized. The results show that the maximum intrinsic viscosity and up to 94% yields of the hybrid polymer can be achieved using initiator concentration of 0.3% with acrylamide monomer mass fraction of 20% under solution polymerization at 40 °C for 7 h. The physicochemical properties of this hybrid flocculant were characterized with TEM, FTIR spectra, TGA, and conductivity. It was found that a chemical bond exists between Fe(OH)3 colloid and polyacrylamide chains in the FHPAM. The application of the hybrid polymer for the treatment of 2.5 g L−1 kaolin suspension indicates that it had an excellent flocculation capacity and its flocculation efficiency was much better than that of commercial available polyacrylamide (PAM) and polymeric ferric sulfate (PFS). The optimal conditions for the flocculation treatment of kaolin suspension were the FHPAM dosage of 40 mg L−1 at pH 7.0. The thermodynamic parameters for the flocculation process were calculated based on a statistical model. Interpretation of the results was given.

► The preparation of a novel Fe(OH)3–PAM hybrid polymer flocculant is achieved via free radical solution polymerization.
► Flocculation of kaolin suspensions using this novel Fe(OH)3–PAM hybrid polymer flocculant is revealed in this study.
► The statistical model was first applied for calculating the thermodynamic parameters for the kaolin flocculating process.