The hydroandradite (HA) is an efficient and ideal desilication product to deal with the bauxite and red mud based on the alkali-thermal process, while the selection of iron source is crucial for the HA generation. This work investigates the effects of various natural iron minerals on the alkali-thermal formation HA in aluminate solution by comparing with synthetic sodium ferrate. The Gibbs free energy changes of HA formation with different iron oxides were calculated based on the complex silicate theory, and the preferential conversion order for HA formation was obtained thermodynamically. The solubility data of various iron minerals in aluminate solution were determined and correlated by the Apelblat model. The contribution order of iron minerals for HA formation was obtained, and the goethite is the best alternative to replace sodium ferrite by comparing to hematite and magnetite. The phase transformation of HA is above 80% in the presence of goethite, and the alkali content in reaction product is as low as 0.20%. Moreover, the effect mechanism of goethite on HA formation was discussed and established.

中文翻译：

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碱热过程中铁矿物对水钙铁矿形成的影响


水钙铁矿（HA）是一种基于碱热法处理铝土矿和赤泥的高效、理想的脱硅产品，而铁源的选择对于HA的生成至关重要。本工作通过与合成高铁酸钠进行比较，研究了各种天然铁矿物对铝酸盐溶液中碱热形成 HA 的影响。基于复合硅酸盐理论，计算了不同铁氧化物形成HA的吉布斯自由能变化，并从热力学上得到了HA形成的优先转化级。各种铁矿物在铝酸盐溶液中的溶解度数据通过 Apelblat 模型确定并关联。得出了铁矿物对HA形成的贡献顺序，与赤铁矿和磁铁矿相比，针铁矿是替代铁酸钠的最佳替代品。在针铁矿存在下，HA的相变率在80%以上，反应产物中碱含量低至0.20%。此外，还讨论并建立了针铁矿对HA形成的影响机制。