Preparation, characterization and coagulation behaviour of polyferric magnesium silicate (PFMSi) coagulant

Abstract

A composite coagulant polyferric magnesium silicate (PFMSi) was synthesized by co-polymerization. The structure and morphology of PFMSi were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscope microphotographs; meanwhile, the coagulation efficiency was evaluated under different ratios of Fe/Si, Mg/Si, basicity ([OH]/[M] ratio), and dosage. The results suggested that the PFMSi coagulant shows an amorphous phase structure, and new chemical compounds had been formed; simultaneously, the different preparation conditions had major effects on coagulation performance. Additionally, the raw water collected from Pearl River was used as a treated water sample to verify the coagulation efficiency of PFMSi. Overall, it is suggested that PFMSi is an efficient coagulant in the removal of turbidity, UV254 and total organic carbon, and it shows a markedly better coagulation performance than polymeric aluminium and non-modified coagulant. The study of coagulation kinetics and zeta potential showed that adsorption-bridging was the main mechanism for the introduction of silicon.