Comparison and evaluation of alumino-silicate samples as a dual source of alumina and potash values

The current study evaluates mica, sericite, diaspore, and feldspar to extract aluminum and potassium values. Mechanical and thermal activation followed by HCl leaching is systematically investigated. Milling improved the surface area of mica, diaspore, and sericite (40-50 m(2)/g), whereas feldspar (32 m(2)/g) showed a limited response. Mica and sericite yielded 75-80% aluminum extraction, and diaspore yielded 70% potassium extraction after 8 h milling. The low alumina content in the feldspar and hard phase in the diaspore is responsible for the inadequate size reduction with limited aluminum dissolution (40-45%). The thermal activation energy of the NaOH baking for diaspore was 400 kJ/mol, mica (282 kJ/mol), and sericite (330 kJ/mol). The aluminum extraction was 72-80%, and potassium extraction was 55-84% at varying SiO2/Al2O3 ratios. The techno-economic assessment showed that alkali thermal treatment (8.1-12.6 kWh/kg Al2O3) consumed less energy than the milling treatment (28.9-37.9 kWh/kg Al2O3). Additionally, the specific HCl consumption is minimal in mica (1.85 kg), followed by diaspore (2.51 kg), sericite (5.47 kg), and feldspar (6.39 kg).