Non-linear hydrodynamic effects on iron recovery from fine tailings in a fluidized bed separation column

The increasing generation of fine iron ore tailings has intensified the search for alternative beneficiation technologies capable of overcoming the limitations of conventional separation routes. In this study, a mineral separation column operating under a controlled fluidized bed regime was investigated as a physical separation approach for the recovery of iron from fine tailings. The tailings were characterized in terms of particle size distribution and moisture content, confirming their predominantly fine nature and challenging behavior for traditional gravity and flotation processes. A Box–Behnken experimental design was applied to systematically evaluate the effects of fluidization velocity, solids mass, and collection height on iron recovery. The statistical analysis demonstrated that the process is governed by significant main effects, interactions, and quadratic terms, highlighting its intrinsically non-linear behavior. Analysis of variance confirmed the adequacy of the quadratic model, with no significant lack of fit, ensuring reliable interpretation of the experimental results. Response surface and contour analyses revealed well-defined optimal operating regions, in which iron recovery was maximized without compromising bed stability. The results showed that intermediate fluidization velocities, combined with suitable solids loading and collection heights, promote a favorable balance between drag forces, gravitational effects, and particle–particle interactions, leading to efficient stratification within the separation column. The strong agreement between experimental data, statistical modeling, and hydrodynamic interpretation demonstrates the robustness and predictability of the proposed separation process. Compared to conventional beneficiation routes, the fluidized bed separator exhibits greater operational stability and reduced sensitivity to feed variability, indicating its potential for industrial application and scale-up. The findings provide a solid technical basis for the development of innovative and sustainable strategies for iron recovery from fine mineral tailings.