This paper focuses on the scandium speciation in bauxite residues of different origin. Insights into mineral-chemical similarities and differences of these materials will be presented and links to their natural geological background discussed. The presented research should provide fundamental knowledge for the future development of efficient and viable technologies for Sc-recovery from bauxite residues derived from different bauxites and accumulating at different localities. In total, five bauxite residues were investigated which originated from Greece, Germany, Hungary and Russia (North Ural & North Timan) using a combination of different analytical tools. Those included: laser ablation inductively coupled plasma mass spectrometry, X-ray absorption near edge structure (XANES) spectroscopy, μ-Raman spectroscopy as well as scanning electron microscopy and electron microprobe analyses. X-ray fluorescence and inductively coupled plasma mass spectrometry were used to determine the overall chemical composition. The investigated samples were found to exhibit a relatively homogenous distribution of Sc between the larger mineral particles and the fine-grained matrix except for Al-phases like diaspore, boehmite and gibbsite. These phases were found to be particularly low in Sc. The only sample where Sc mass fractions in Al-phases exceeded 50 mg/kg was the Russian sample from North Ural. Fe-phases such as goethite, hematite and chamosite (for Russian samples) were more enriched in Sc than the Al-phases. In fact, in Greek samples goethite showed a higher capacity to incorporate or adsorb Sc than hematite. Accessory minerals like zircon, rutile/anatase and ilmenite were found to incorporate higher mass fractions of Sc (>150 mg/kg), however, those minerals are only present in small amounts and do not represent major host phases for Sc. In Russian samples from North Ural an additional Ca-Mg rich phase was found to contain significant mass fractions of Sc (>500 mg/kg). μ-XANES spectroscopy was able to show that Sc in bauxite residue occurs adsorbed onto mineral surfaces as well as incorporated into the crystal lattice of certain Fe-phases. According to our observations the bauxite type, i.e. karstic or lateritic, the atmospheric conditions during bauxitization, i.e. oxidizing or reducing, and consequently the dominant Sc-bearing species in the primary bauxite influence the occurrence of Sc in bauxite residues. In karstic bauxites, underlying carbonate rocks can work as a pH-barrier and stabilize Sc. This prevents the Sc from being mobilized and removed during bauxitization. Hence, karstic bauxites are more prone to show a Sc enrichment than lateritic bauxites. Reducing conditions during bauxitization support the incorporation of Sc into clay minerals such as chamosite, which can dissolve and reprecipitate during Bayer processing causing Sc to be redistributed and primarily adsorb onto mineral surfaces in the bauxite residue. Oxidizing conditions support the incorporation of Sc into the crystal lattice of Fe-oxides and hydroxides, which are not affected in the Bayer process. The genetic history of the bauxite is therefore the major influential factor for the Sc occurrence in bauxite residues.

本文着眼于不同来源的铝土矿渣中的spec形态。将介绍这些材料的矿物化学相似性和差异性，并讨论其天然地质背景的链接。提出的研究应该为将来开发有效和可行的从不同铝土矿中并在不同地方积累的铝土矿残渣中回收Sc的技术提供基础知识。总共使用了多种分析工具，对来自希腊，德国，匈牙利和俄罗斯（北乌拉尔和北提曼）的五个铝土矿残留物进行了调查。其中包括：激光烧蚀电感耦合等离子体质谱法，X射线吸收近边缘结构（XANES）光谱，μ拉曼光谱以及扫描电子显微镜和电子探针分析。X射线荧光和电感耦合等离子体质谱法用于确定总体化学组成。发现所研究的样品在较大的矿物颗粒和细粒基质之间表现出相对均匀的Sc分布，除了硬铝矿，勃姆石和菱镁矿等Al相。发现这些相的Sc特别低。Al相中Sc的质量分数超过50 mg / kg的唯一样品是来自北乌拉尔的俄罗斯样品。铁相，如针铁矿，赤铁矿和硫铁矿（用于俄罗斯样品）比铝相富集更多的Sc。实际上，在希腊样品中，针铁矿的掺入或吸附Sc的能力比赤铁矿高。锆石等辅助矿物 发现金红石/锐钛矿和钛铁矿掺入较高质量分数的Sc（> 150 mg / kg），但是这些矿物质仅少量存在，并不代表Sc的主要宿主相。在来自北乌拉尔的俄罗斯样品中，发现另外的富含Ca-Mg的相含有大量的Sc（> 500 mg / kg）。μ-XANES光谱能够显示铝土矿残留物中的Sc发生吸附到矿物表面上以及掺入某些Fe相的晶格中。根据我们的观察，铝土矿类型（即岩溶或红土），铝土矿化（即氧化或还原）过程中的大气条件以及主要铝土矿中主要的含Sc物种会影响铝土矿残留物中Sc的发生。在岩溶铝土矿中 下层碳酸盐岩可以作为pH屏障并稳定Sc。这防止了Sc在铝土化过程中被动员和移除。因此，与红土铝土矿相比，岩溶铝土矿更容易表现出Sc富集。铝土矿化过程中的还原条件有助于将Sc掺入粘土矿物（例如硅铁矿）中，在拜耳加工过程中它会溶解和再沉淀，导致Sc进行重新分布，并主要吸附到铝土矿残余物中的矿物表面上。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。这防止了Sc在铝土化过程中被动员和移除。因此，与红土铝土矿相比，岩溶铝土矿更易于显示Sc富集。铝土矿化过程中的还原条件有助于将Sc掺入粘土矿物（例如硅铁矿）中，在拜耳加工过程中它会溶解和再沉淀，导致Sc进行重新分布，并主要吸附到铝土矿残余物中的矿物表面上。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。这防止了Sc在铝土化过程中被动员和移除。因此，与红土铝土矿相比，岩溶铝土矿更容易表现出Sc富集。铝土矿化过程中的还原条件有助于将Sc掺入粘土矿物（例如硅铁矿）中，在拜耳加工过程中它会溶解和再沉淀，导致Sc进行重新分布，并主要吸附到铝土矿残余物中的矿物表面上。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。铝土矿化过程中的还原条件有助于将Sc掺入粘土矿物（例如硅铁矿）中，在拜耳加工过程中它会溶解和再沉淀，导致Sc进行重新分布，并主要吸附到铝土矿残余物中的矿物表面上。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。铝土矿化过程中的还原条件有助于将Sc掺入粘土矿物（例如硅铁矿）中，在拜耳加工过程中它会溶解和再沉淀，导致Sc进行重新分布，并主要吸附到铝土矿残余物中的矿物表面上。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。氧化条件支持将Sc掺入Fe-氧化物和氢氧化物的晶格中，而在Bayer过程中不受影响。因此，铝土矿的遗传历史是铝土矿残留物中Sc发生的主要影响因素。