Nepheline syenite as a sustainable remineralizer: technological characterization and K-release potential

Silicate rocks, such as nepheline syenite, present a sustainable alternative to reduce fertilizer imports due to their high K content and reactivity^1,2. Samples from GO and RJ were characterized and activated to assess their use³. The GO sample exhibits 8.07% structural K₂O, 90% ≤1 mm, and mineralogy composed of feldspars, muscovite, and dolomite. Activation with CaO and calcination at 1000 °C increased K extraction to 4.5% (citric acid) and 6.5% (oxalic acid), representing a 16-fold increase over the in natura rock. For the RJ samples (fresh and weathered rocks), characterization by XRF, XRD, FTIR, SEM, TGA, and Zeta potential revealed microcline and quartz as phases, with K₂O contents of ~9.5%. The fresh rock presented 85% ≤2 mm, while the weathered sample retained approximately 50% in this fraction. Analyses confirmed thermal stability and negative surface charge across pH 1–13, evidencing the technical potential of this rock as a sustainable remineralizer.