Magnetic beneficiation of nepheline syenite from the Rio Pardo Stock, Brazil: Influence of particle size

This study investigates an iron removal process combining size classification and magnetic separation applied to nepheline syenite from the Rio Pardo Stock (Southern Alkaline Province, Bahia, Brazil) to evaluate its suitability for ceramic and glass applications. The rock consists predominantly of feldspars (microcline and albite), with subordinate nepheline, cancrinite and biotite. Following crushing, grinding and particle-size classification, the −0.85 to +0.053 mm fractions were treated by dry Rare Earth Roll Magnetic Separation (13,000 G), whereas the <0.053 mm fraction was processed separately by Wet High-Intensity Magnetic Separation (WHIMS) under the same magnetic field. The influence of particle size on iron removal was evaluated. The highest non-magnetic recoveries (81.5–84.4 wt.%) were achieved in the intermediate particle-size fractions (0.50–0.15 mm), whereas the lowest Fe ₂ O ₃ content (0.36 wt.%) was obtained in the −0.075 + 0.053 mm fraction. Although the <0.053 mm fraction yielded the highest non-magnetic mass yield (93.0 wt.%), its Fe ₂ O ₃ content increased to 0.50 wt.%. Considering only the material subjected to magnetic separation (4771.4 g), the non-magnetic product represented 80.18 wt.% of the magnetic separation feed. The results demonstrate the beneficiation potential of the Rio Pardo nepheline syenite deposit, producing concentrates with Fe ₂ O ₃ contents as low as 0.36 wt.% and high alkali recoveries suitable for ceramic and glass applications.