Use of magnetite nanoparticles and magnetic separation for the removal of metal(loid)s from contaminated mine soils.

Magnetite nanoparticles have been successfully used for removal and immobilization of contaminants in water, yet their application in soils combined with in situ magnetic separation remains unexplored. We evaluated the effectiveness and optimal conditions for using magnetite nanoparticles combined with magnetic separation to remove metal(loid)s from contaminated mine soils. Soil samples were incubated (15, 45 days) with varying doses of magnetite (0, 25, 50 g kg⁻¹) and moisture (dry, field capacity) and separated using electromagnet or permanent magnet. This technique achieved up to 44 % As, 65 % Cd, 60 % Cu, 47 % Fe, 40 % Mn, 65 % Pb, and 62 % Zn removal, leaving minimal residual magnetite in the soil. These high removal efficiencies were attributed to the nanoparticles' magnetic properties, adsorption capacity and ability to form aggregates with soil particles. Optimal conditions were 25 g kg⁻¹ of magnetite incubated for 45 days at field capacity and separated by the electromagnet. Higher doses (50 g kg⁻¹) offered minimal improvement at increased costs. The combined use of magnetite nanoparticles and in situ magnetic separation demonstrated a low-impact and cost-effective method for reducing metal(loid) concentrations to levels that facilitate subsequent soil remediation strategies.