Ferrimagnetic coagulation process for phosphate ion removal using high-gradient magnetic separation

An efficient magnetic separation system for phosphate ion removal has been studied for developing a practical environmental protection technology for water purification in rivers, lakes, etc. using ferrimagnetic fine particles (FMFPs), which can be prepared from FeCl2 and FeCl3,aqueous solutions. With 15 mg/L of FeCl3 solution, without the addition of FMFP, phosphate ion recovery increased from 20 to 80% with increasing magnetic field from 0.8 to 8 T. By the addition of 5 mg/L of FMFP with 15 mg/L of FeCl3 solution, above 95% recovery was achieved in a wide range of magnetic field (H = 0.8-8 T). A high magnetic field gradient generated in the vicinity of steel wool caused the enhancement of the magnetic coagulation of the complex with phosphate ion and Fe(III) ion, and the paramagnetic iron-phosphate complexes were attracted to FMFP in the reactor, which resulted in high (95%) recovery in a wide range of magnetic fields.