Abstract In this article, we present the results of the mineralogical quantification of airborne dust from an urban area located in the Brazilian state of Minas Gerais in the vicinity of a gold mine. Three samples were collected at different points to assess spatial consistency. Results showed that the mineralogy, in relation to both major minerals and accessory minerals, is very similar for all samples, being predominantly composed of muscovite and quartz, which together account for around 60% to 75% by weight. The accessory minerals are clinochlore, albite, dolomite, calcite and kaolinite and the averages for each range from 4% to 13%. The only trace mineral with concentration below 1% was pyrite which has a concentration below 1%. The results provide an indication that the mining area is not the sole source of local dust, although the mine's contribution is significant.

Magnetite nanosized particles synthesis was achieved by two different routes. Assessment of microstructure was carried out aiming at comparing the outcome of synthesis parameters on the crystallinity, distribution of particle dimension and magnetic activity of nanosized particles precipitated in aqueous solution. Increasing of the nanoparticles crystallite size by stirring could be evidenced by the results. Temperature does not significantly affect crystallite size and crystallinity. The type of precursor was the factor that most contributed to the definition of crystallinity and particle size distribution. The route which used FeSO4.7H2O as precursor favored large crystallite sizes and crystallinity, while the route which used Fe2SO4.7H2O and FeCl3.6H2O as precursors resulted in much smaller crystallite sizes and crystallinity.

The introduction of magnetic properties in adsorbent materials has the aim of improving solid-liquid separation processes. In this work, a magnetic composite was synthesized through the precipitation of manganese oxide in the presence of magnetite particles using O2 as an oxidant. The composite proved to be chemically and physically stable within a wide range of pH values. The composite characterization indicated that hausmannite (Mn3O4) represents the precipitated manganese phase and that magnetite undergoes no phase transformation during the synthesis. The composite and Mn3O4 particles were used to remove As(III) from aqueous solutions. The magnetic composite and Mn3O4 sample presented high and similar affinity for As(III), with maximum sorptive capacities of 14 mgAs g solid-1 (0.0048 mmolAs m-2solid) and 20 mgAs g solid-1 (0.0049 mmolAs m-2solid), respectively, at pH 5.0. The combination of an active high surface area sorbent (Mn3O4) with a magnetic phase (Fe3O4) allows for efficient As(III) removal and solid/liquid separation.