Magnetic nanoparticle recovery device (MagNERD) enables application of iron oxide nanoparticles for water treatment

An optimized permanent magnetic nanoparticle recovery device (i.e., the MagNERD) was developed and operated to separate, capture, and reuse superparamagnetic Fe₃O₄ from treated water in-line under continuous flow conditions. Experimental data and computational modeling demonstrate how the MagNERD’s efficiency to recover nanoparticles depends upon reactor configuration, including the integration of stainless-steel wool around permanent magnets, hydraulic flow conditions, and magnetic NP uptake. The MagNERD efficiently removes Fe₃O₄ in the form of a nanopowder, up to > 95% at high concentrations (500 ppm), under scalable and process-relevant flow rates (1 L/min through a 1.11-L MagNERD reactor), and in varying water matrices (e.g., ultrapure water, brackish water). The captured nanoparticles were recoverable from the device using a simple hydraulic backwashing protocol. Additionally, the MagNERD removed ≥ 94% of arsenic-bound Fe₃O₄, after contacting As-containing simulated drinking water with the nanopowder. The MagNERD emerges as an efficient, versatile, and robust system that will enable the use of magnetic nanoparticles in larger scale water treatment applications. [Figure not available: see fulltext.]