A new step in the Bayer process has been used to recover NaOH and to reduce its content in red mud. After digestion, the residue is separated from the Bayer liquor and goes through press filters, which enables the recovery of NaOH and decreases the moisture content. It is well known that red mud is one of the most important sources of scandium. For this reason, the goal of this work was to characterize a Brazilian red mud (BRM) for scandium recovery. The sample was collected after the press filter system process. Analysis of energy-dispersive X-ray fluorescence (EDXRF), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), and X-ray diffraction (XRD) was performed. Microwave digestion using an acid mixture was carried out to determine the concentration of the main elements. Fe 2 O 3 represented 40% of the BRM, and the Sc concentration was 43 mg/kg. The SiO 2 content was 24%, which is the highest value found in the literature, whereas the sodium concentration was the lowest. A literature review was carried out to compare results with BRM, as well as the current studies for recovery of scandium by the leaching/ion-exchange process. Scandium recovery using a leaching/ion exchange process may be possible with efficiency higher than 90%. The greatest challenge is the occurrence of silica gel formation during leaching. Graphical abstract

中文翻译：

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压滤系统铝土矿渣的表征：钪提取的比较研究和挑战

拜耳工艺中的一个新步骤已用于回收 NaOH 并降低其在赤泥中的含量。消化后，残渣从拜耳液中分离出来，通过压滤机，可以回收氢氧化钠并降低水分含量。众所周知，赤泥是最重要的钪来源之一。出于这个原因，这项工作的目标是表征用于钪回收的巴西赤泥 (BRM)。在压滤系统过程之后收集样品。进行了能量色散 X 射线荧光 (EDXRF)、扫描电子显微镜/能量色散 X 射线光谱 (SEM/EDS) 和 X 射线衍射 (XRD) 的分析。使用酸性混合物进行微波消解以确定主要元素的浓度。Fe 2 O 3 占 BRM 的 40%，Sc 浓度为 43 mg/kg。SiO 2 含量为24%，这是文献中发现的最高值，而钠浓度最低。进行了文献综述以比较与 BRM 的结果，以及目前通过浸出/离子交换过程回收钪的研究。使用浸出/离子交换工艺回收钪可能效率高于 90%。最大的挑战是在浸出过程中会形成硅胶。图形概要 使用浸出/离子交换工艺回收钪可能效率高于 90%。最大的挑战是在浸出过程中会形成硅胶。图形概要 使用浸出/离子交换工艺回收钪可能效率高于 90%。最大的挑战是在浸出过程中会形成硅胶。图形概要