Magnetic field-induced self-assembly of urchin-like polymeric particles: mechanism, dispersity, and application in wastewater treatment

Pollutant treatment is critical in modern society and existing purification methods often cannot address this problem quickly and economically. Recently, hierarchically organized particles have attracted much academic attention in wastewater treatment because of their unusual geometry associated with the favorable properties of nanoscale units and three-dimensional assemblies synchronously. Here, we synthesized hierarchically organized Fe3O4/poly(glycidyl methacrylate-ethylene glycol dimethacrylate) (poly(GMA-EDMA)) meso-particles (UPPs) by a magnetic field-induced self-assembly strategy. Under the orientation of the external magnetic field, poly(GMA-EDMA) nanoparticles polymerized by GMA and EDMA organically self-assembled around Fe3O4 nanoparticles into mesoscale UPPs. The obtained UPPs showed high dispersity in both aqueous and organic solutions due to that the spikes on the surface of UPPs weaken attractive van der Waals forces between particles. The high dis-persity in solutions guarantees the high mass transfer efficiency between UPPs and solutions. Moreover, the incorporation of Fe3O4 nanoparticles endows UPPs with a fast reversible macroscopic assembly & disassembly ability by controlling the external magnetic field, which is beneficial to the collection and regeneration of UPPs. Taking advantage of the features, we grafted iminodiacetic acid (IDA) on the surface of UPPs to obtain a heavy metal ion adsorbent. The IDA-modified UPPs showed high adsorption capacities, fast adsorption rates, and good recyclability for Cu2+ and Pb2+. Besides, the IDA-modified UPPs can allow to be loaded by beta-FeOOH nano-catalyst, showing a good photocatalytic performance toward methylene blue, promising a great potential in wastewater treatment.