Xiangxia Wei1 Jun Ding1

1, National University of Singapore, Singapore, , Singapore

Ferrite-based magnetic material has wide applications due to excellent chemical stability, good mechanical hardness, and remarkable magnetic properties. However, it is limited to be processed into thick films or simple shapes by the exisiting approaches. To obtain complex geometries for the extensive applications, extrusion-based three-dimensional (3D) printing is attractive. Herein, a soft magnetic ferrite ((Ni,Zn)Fe2O4) with the desired mesh architecture is obtianed and applied as a magentic filter for the treatment of heavy-metal-contaminated water due to its serious toxicity. This filter can effectively capture the quasi-superparamagnetic Fe3O4 nanoparticles after sufficient adsorption of heavy metal ions under an external magnetic field as low as 0.07 T instead of the traditional strong field up to 2 T. Interestingly, after one single filtration process, the heavy metal concentration could be significantly decreased from 1 mg L-1 to satisfy the drinking water standard recommended by the World Health Organization (e.g., <0.01 mg L-1 for Pb(II)). In the end, the fabricated filter is convenient to be recovered by simple ultrasonic washing and nanoparticles can be well-regenerated by the adjustment of pH, which can avoid byproducts and secondary pollution. Overall, a proof-of-concept magnetic device for effective heavy metal removal is demostrated by a combination of adsorption and subsequent low-field separation using the 3D-printed magnetic filter. It will also have a great impact on other environmental and biomedical issues, for example, antibiotics contamination.