Recovery of nanoferrites from metal bearing wastes: Synthesis, characterization and adsorption study

Manganese ferrite (MnFe2O4) nanoparticles were produced by surfactant-assisted method using as metal sources both synthetic chemicals and industrial wastes (spent Li-ion batteries and pyrite ash) and performing different thermal treatments (microwave, autoclave, furnace at different temperature, oven). Nanoferrites obtained using synthetic precursor by microwave-surfactant assisted hydrothermal route showed distinct XRD peak of spinel phase; nanoparticles were characterized by SEM, BET, magnetism and adsorption tests. Nanoferrites were found to have plate shape with 715 nm width size, 5.23 emu/g, 57 ± 1 m2/g surface size, 0.59 ± 0.03 mmol/g arsenic and 0.80 ± 0.04 mmol/g copper adsorption capacity. Thermal treatment performed during synthesis by microwaves gave the best results in terms of crystallinity, surface area, magnetism and metals sorption capacity. In particular, the ideal nanoparticles were found to have octahedron shape with 22.3 nm size, 38.63 emu/g magnetism, 159 ± 1 m2/g surface size, 0.63 ± 0.03 mmol/g As(V) and 1.17 ± 0.05 mmol/g Cu(II) adsorption capacity. Then experimental findings showed that using the same optimized conditions (microwave assisted hydrothermal route) waste precursors gave nanoferrites with different morphology, similar mineralogical phase, and improved characteristics in terms of magnetic properties, surface area and metal sorption capacity.