The Rapid Release Process and Mechanism of Nutrients in Biomimetic Weathered Granite Rock Powder

Ecological restoration of waste slag sites is often constrained by topsoil scarcity and nutrient deficiency. Therefore, this study investigated organic acid-matured granite rock powder (M-GRP) to evaluate its mineral nutrient-release behavior and structural evolution, with the aim of developing it as a compost mineral additive. The results showed that 0.2 mol/L malonic acid, a solid-to-liquid ratio of 1:75, and maturation at room temperature for 8 h provided effective nutrient release from granite rock powder. Characterization analysis showed that protons and organic groups in malonic acid promoted the dissolution of feldspar and illite in granite rock powder, accompanied by the substantial dissolution of clinochlore and calcite. Feldspar and illite exhibited severe dissolution at edges and protrusions, forming pits and pores. Malonic acid treatment decreased the unit-cell volume and interplanar spacing of the surviving mineral phases and interplanar spacing, and increased surface roughness, lattice defects, and surface disorder. Quartz remained comparatively stable, with its morphology and crystal structure preserved. In addition, the specific surface area of M-GRP increased, accompanied by changes in its pore structure and pore-size distribution. These results provide a theoretical basis and technical support for the resource utilization of rock powder.