Magnetic Metal–Organic Framework Enhanced Inorganic Coagulation for Water Purification

Abstract

Green water treatment technologies are widely popular, and magnetic coagulation is one of the most popular methods and has been successfully applied in industry. Among them, magnetic seeds are crucial for the flocculation of contaminants. The objective of this work was to investigate the potential of magnetic metal–organic frameworks (MMOFs) as a seed in assisting polymeric ferric sulfate (PFS) flocculant, specifically exploring their applicability in algal-contaminated water. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, ferrite timing spectroscopy, and flocculation tests were used to characterize the structure and flocculation properties of MMOFs and PFS (PFS-MMOFs) composites, highlighting the stability of magnetic seed MMOFs and the flocculation effect of the composites. The results show that MMOFs have good dispersion and stability in acidic PFS solutions, which are favorable for engineering applications. MMOFs and PFS are bonded by hydrogen bonds, which enhance the polarity and dispersion of MMOFs, as well as the molecular chains of PFS. In the presence of MMOFs, it affected the distribution of iron species in the PFS, which means that the performance of coagulation may be changed. Coagulation with PFS-MMOFs was effective under different hydraulic conditions. It also showed better results than PFS in terms of dissolved organic carbon (DOC) removal and ultraviolet absorption value at 254 nm (UV254). In addition, the PFS-MMOFs in algal-infested waters were superior to the PFS. Overall, the findings tested in this study indicated that MMOFs are good magnetic seeds for remediation of water pollution in conjunction with PFS, potentially enhancing conventional coagulation.