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.

中文翻译：

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一种中低品位铝土矿生产氧化铝的清洁方法及硅钾复合肥的联产方法

优质铝土矿的稀缺和赤泥堆积的增加严重阻碍了氧化铝行业的可持续发展。本研究提出了一种新的“钙化-钾碱”（CPA） 方法，该方法利用 KOH 而不是 NaOH 来模拟拜耳溶解过程。该方法将产物从水合硅酸钠-铝酸盐 （Na2O-Al2O3-1.7SiO2-nH2O） 转化为硅酸钾-铝酸盐 （K2O-Al2O3-SiO2）。在最佳条件下（240 g/L K2O、260 °C、钙硅比 0.2 和 60 分钟反应时间），氧化铝提取率达到 82.53 %，产品中氧化铝含量为 99.4 %。固体产物还含有 19.82% 的 SiO2 和 11.52% 的 K2O，有效 SiO2 和 K2O 分别占 26.8% 和 88.2%。与拜耳法相比，CPA 显著提高了氧化铝浸出率，同时确保转化产品符合硅钾肥的相关标准。此外，转化后的赤泥可用于生产矿物二氧化钾肥，解决了赤泥积累问题，缓解了钾肥的供需压力。这种方法不仅提高了经济效益，而且为中低品位铝土矿的高效利用和清洁生产提供了新的参考方案。