Scaling up magnetic filtration and extraction to the ton per hour scale using carbon coated metal nanoparticles

To fully benefit of the promising features of magnetic nanoparticle filtration as a large scale liquid purification method effective ways to remove nanoparticles from rapidly moving streams are required. The present work investigates the feasibility of pilot scale magnetic filtration at affordable costs and space requirements as a result of significantly improved magnetization when using metal nanoparticles. Using standard equipment, we demonstrate continuous magnetic extraction at 1 m3 water per hour. Highly stable carbon coated metal nanoparticles were used as mobile extraction agents due to their excellent accessibility and fast separation. The nano-size of the particles reduced the adsorption time and thus permitted fast processing of water. Nanoparticles with a metal core (>140 A m2 g−1) instead of traditional iron oxide allowed efficient particle removal in a non-optimized, steel wool filled cartridge of 135 cm3 at a flow rate of 1 m3 h−1. Instead of electromagnets with considerable energy consumption, permanent magnets (no electrical supply needed) could be used. These findings confirmed recent suggestions on the use of magnetic filtration for the treatment of large volumes without significant pressure drop.