A clean method for alumina production and the coproduction of silicon-potassium compound fertilizer from middle and low grade bauxite ore

The scarcity of high-quality bauxite and the increasing accumulation of red mud significantly hinder the sustainable development of the alumina industry. This study proposes a novel “calcification-potassium alkali” (CPA) method, which utilizes KOH instead of NaOH to simulate the Bayer process for dissolution. This method transforms the product from hydrated sodium silicate-aluminate (Na₂O-Al₂O₃-1.7SiO₂-nH₂O) to potassium silicate-aluminate (K₂O-Al₂O₃-SiO₂). Under optimal conditions (240 g/L K₂O, 260 ℃, calcium-silicon ratio 0.2, and 60 min reaction time), the alumina extraction rate reached 82.53 %， with a product containing 99.4 % alumina. The solid product also comprised 19.82 % SiO₂ and 11.52 % K₂O, with effective SiO₂ and K₂O accounting for 26.8 % and 88.2 %, respectively. Compared to the Bayer method, CPA markedly enhances the alumina leaching rate while ensuring that the transformation product complies with the relevant standards for silica-potash fertilizer. Furthermore, the transformed red mud can be utilized in the production of mineral silica-potassium fertilizer, addressing the issue of red mud accumulation and alleviating the supply and demand pressures for potash fertilizer. This approach not only improves economic benefits but also offers a new reference scheme for the efficient utilization and clean production of low and medium-grade bauxite.