Recycled α-Fe2O3 nanoparticles adsorbents from Nd-Fe-B waste for methylene blue adsorption

Nanoparticles α-Fe2O3 were prepared using the waste liquid after recycling rare earths in Nd-Fe-B waste magnets. The most α-Fe2O3 particles have around 60-120nm diameters with the surface area of 144.51 m2 g -1 and pore size of around 5.0 nm. Methylene blue was used as a model pollutant to study the adsorption properties of the obtained α-Fe2O3 nanoparticles. The effects of contact time, pH value, loading mass of α-Fe2O3, and temperatures on the adsorption behavior were investigated. Results indicated that ultra-refined α-Fe2O3 particles can achieve an adsorption rate of 98% for the removal of methylene blue from waste liquids. Also, the removal of methylene blue by α-Fe2O3 particles presented an adsorption isotherm process which strongly fitted the pseudo-second-order kinetics model and Langmuir equation. The present work demonstrates a sustainable and efficient methodology for the re-use of Fe from magnet wastes and removal of MB, opening a promising and cost-effective avenue for the sewage-cleaning.