Effect of EDTA organic coating on the spin canting behavior of maghemite nanoparticles for lead (II) adsorption

EDTA functionalized γ-Fe₂O₃ nanoparticles, with controlled-sizes between 4 and 8 nm and specific surface areas up to 272 m²/g, were prepared using modified co-precipitation routes and systematically characterized using local, surface and global experimental methods. The functionalized nanoparticles behave as a magnetic trilayer-like system formed by ferrimagnetic spinel-like grains, a spin-glass-like layer as a spacer, and a cover of iron hydroxide layer with antiferromagnetic interactions. The fraction of the Fe canted spins in the spacer layer and the specific surface area are directly related to the amount of the iron hydroxide thin layer. Small (large) amounts of the iron-hydroxide layer on the nanoparticle surfaces reduce (increase) the canted Fe spin fraction, decreasing (increasing) the exchange bias effect found in the functionalized NPs. The nanoparticles with the largest specific area were applied for Pb(II) adsorption and showed a reduction of Pb(II) concentration in contaminated water to a limit less than 10 μg L⁻¹ for an equilibrium time of 7 h. The EDTA tailored γ-Fe₂O₃ nanoparticles showed efficient Pb(II) adsorption, easy magnetic removal, and recycling properties, making this nanohybrid adsorbent a good potential candidate for a water cleaning process.