Reusable superparamagnetic raspberry-like supraparticle adsorbers as instant cleaning agents for ultrafast dye removal from water

Herein, a particle system of so‐called raspberry‐like supraparticles, capable of dye removal from water within a few seconds, is presented. These particles are micron sized and assembled of smaller silica nanoparticles as adsorber and iron oxide nanoparticles which act, due to their superparamagnetic properties, as switchable magnets. With this particle design, it is possible to tailor the adsorber structure and adjust the magnetic properties. Using very small silica nanoparticles (10 nm) combined with superparamagnetic iron oxide nanoparticles (10 nm), to build the supraparticles, turned out to result in a system with which a deeply methylene blue dye colored water could be clarified within 60 seconds via dye adsorption on the particles and their subsequent magnetic separation. A comparison with assembled supraparticles from larger primary nanoparticles revealed the role of the primary nanoparticles to create a porous particle structure which comes with an apparent capillary effect to take up the dye. The system could be regenerated either thermally or by acid treatment and reused consecutively as magnetically recoverable adsorber. Due to the building block principle of the system, modification towards other adsorption tasks should be easily possible this therefore turns such particle systems into an ideal platform to build tailored adsorbers.