A rotary magnetic separator integrating nanoparticle-assisted water purification: Simulation and laboratory validation

This work introduces a continuous flow process for the implementation of magnetic nanoadsorbents in drinking water treatment practices based on their complete recovery using a rotary separation setup with an arrangement including the use of permanent magnets. Magnetostatic analysis and computational fluid dynamics were combined to simulate the generated magnetic field of a Halbach array of magnets fixed in a PMMA disk, and the flow behavior of a Sn-based magnetic nanocomposite dispersion under the influence of the alternating field. The rotating speed and direction, the flowrate of the dispersion and the immersion level into the dispersion tank were proven to be the critical parameters to maximize capture and separation of the nanocomposite from the flowing water. To validate the efficiency of the designed setup, the corresponding magnetic separator was built and adapted as a unit in a sequence with a stirring tank which brings Cr(VI)-polluted water in contact with the nanocomposite. The experimental operation involved the use of a tin oxyhydroxide (abhurite), a phase known for its high uptake efficiency on Cr(VI), loaded with 20%wt. Fe3O4 nanoparticles which act as the magnetic carrier for the post-treatment recovery. The developed pilot unit achieved a complete water purification, for Cr(VI) concentrations up to 100 μg/L even for low contact times such as 15 min whereas the in line magnetic separator offered a total (100 %) capture of the nanocomposite providing solid-free and purified water.