The Bayer process primarily focuses on alumina extraction, often overlooking other valuable elements. Lacking proper treatment, the resulting red mud poses significant ecological threats. Converting iron-containing phases, such as goethite and hematite, to magnetite during leaching is essential for improving alumina extraction and recovering iron resources. This study addresses this challenge by leveraging the reductive thermal properties of starch within an alkaline thermal environment to facilitate the transformation and recovery of iron oxides. We systematically investigated the effects of various process parameters, and analyzed hematite transformation using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and chemical analysis. The surface properties were characterized through zeta potential, wettability, and solvation tendency assessments. Our results indicate that increased temperature, mass ratio of starch to hematite(S/H), and sodium oxide concentration significantly promote hematite transformation. During simulated Bayer leaching at 260 °C, with 240 g/L sodium oxide, a mother liquor molecular ratio of 3.1, a liquid-to-solid ratio of 4, and a starch to iron oxide mass ratio of 0.5, we achieved an iron oxide reduction rate of 96.91 % after 60 min. Magnetite and de-silicated product (DSP) exhibit distinct surface properties compared to hematite, which facilitates the aggregation, growth, and separation of hematite from DSP. Furthermore, the direct addition of starch to the high-temperature Bayer leaching process of high-iron bauxite enhances the transformation and separation of iron phases while reducing sodium oxide content in red mud. This work represents significant progress in the efficient recovery of iron resources during alumina production, reducing red mud emissions and promoting the green and sustainable development of the alumina industry.

中文翻译：

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创新的淀粉基碱热还原赤铁矿：矿物相重构及其在拜耳工艺中的潜力的基础研究

拜耳工艺主要侧重于氧化铝提取，通常忽略其他有价值的元素。由于缺乏适当的处理，由此产生的红泥构成了严重的生态威胁。在浸出过程中将针铁矿和赤铁矿等含铁相转化为磁铁矿对于改进氧化铝提取和回收铁资源至关重要。本研究通过利用淀粉在碱性热环境中的还原热特性来促进氧化铁的转化和回收，从而解决了这一挑战。我们系统地研究了各种工艺参数的影响，并使用 X 射线衍射 （XRD）、X 射线荧光 （XRF）、扫描电子显微镜 （SEM） 和化学分析分析了赤铁矿的转变。通过 zeta 电位、润湿性和溶剂化倾向评估来表征表面特性。我们的结果表明，温度升高、淀粉与赤铁矿质量比 （S/H） 和氧化钠浓度显著促进赤铁矿转化。在 260 °C 下模拟拜耳浸出过程中，氧化钠为 240 g/L，母液分子比为 3.1，液固比为 4，淀粉与氧化铁质量比为 0.5,60 min 后氧化铁还原率为 96.91%。与赤铁矿相比，磁铁矿和脱硅产物 （DSP） 表现出独特的表面特性，这有利于赤铁矿与 DSP 的聚集、生长和分离。此外，在高温拜耳浸出过程中，高铁铝土矿的淀粉直接添加增强了铁相的转变和分离，同时降低了赤泥中的氧化钠含量。 这项工作代表了氧化铝生产过程中铁资源高效回收、减少赤泥排放以及促进氧化铝行业的绿色和可持续发展的重大进展。