Here we show that spontaneous oxidation of MnO nanoparticles into MnO/Mn 3 O 4 core/shell nanoparticles has the effect of a local pressure, decreasing the MnO cell parameter and increasing strain, resulting in the increase of the MnO antiferromagnetic/paramagnetic transition temperature T N . These effects are more severe in smaller nanoparticles.

Magnetic separation in water remediation processes is of great interest in current environmental technologies. An important aspect in this field has been the development of efficient sorbents for water purification units, namely by exploiting other functionalities that might originate more sustainable technologies. This chapter describes the state-of-art on the chemical preparation of magnetic sorbents comprising inorganic particles and biopolymer matrices. Fundamental aspects related to nanoparticle synthesis of iron oxides and nanomagnetism will be first addressed. The use of these particles in biopolymers matrices such as polysaccharides will be then reviewed as an innovative strategy aiming at production of eco-friendly sorbents for magnetic separation.

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