赤泥中的稀土资源:分布、赋存和提取

REE resources in red mud: distribution, occurrence and extraction

铝土矿中通常含有一定量的稀土元素(REE),氧化铝生产过程导致矿石中几乎所有的REE都富集到赤泥中,其中喀斯特型铝土矿所产生赤泥中的REE含量相对更高,是潜在的REE二次资源,综合利用赤泥中的REE已成为研究热点之一。已有的研究表明,REE分布于赤泥的各个矿物相,包括铝土矿保留下来的矿物相或新形成的矿物相。类质同象可能是其中REE的主要赋存形式,含Fe或Ti的矿物是其主要载体矿物,存在少量REE独立矿物,硅酸盐矿物相或新形成的矿物相也是REE潜在载体矿物。目前,赤泥中REE回收利用多处于实验室研究阶段,包括直接酸浸、焙烧浸出和生物浸出等方法。对比结果表明,直接酸浸和焙烧浸出是有效的赤泥回收REE的方法,但难点是如何增加浸出的选择性,及简化工艺流程。此外,生物浸出的过程更绿色环保,可能成为未来最具前景的回收REE的方法。在回收过程中,设计和发展多元素回收工艺,将Fe、Al、Na、Ti和REE等元素均纳入提取回收流程,并将有用金属回收后所产生的残渣作为制备建筑装饰、催化支撑材料、吸附剂等的原材料,将是赤泥综合利用未来发展方向。

Bauxite usually contains a certain amount of rare earth elements(REE). The production process of alumina leads to the enrichment of almost all REE in the ore into red mud. The content of REE in red mud produced from karst bauxite is relatively high, and is a potential secondary REE resource. The comprehensive utilization of REE in red mud has become one of the research hotspots. Previous studies have shown that the REE is distributed in various mineral phases of red mud, including retained or newly formed mineral phases in bauxite. Isomorphism may be the main occurrence state of REE. Minerals containing Fe or Ti are the main REE carrier minerals. There is only a small amount of REE independent minerals. Silicate or newly formed mineral phases are also the potential REE carrier minerals. At present, the recovery and utilization of REE from red mud are mostly studied in the laboratory research stage, with methods including direct acid leaching, roasting and leaching, and bioleaching. The comparison results show that the direct acid leaching and the roasting and leaching are effective methods for the REE recovery from red mud, but the difficulty is how to increase the selectivity of leaching and to simplify the technological process. In addition, the bioleaching is more environmental friendly and may become the most promising method for recovering REE from red mud in the future. In the recovery process, the multi-element recovery process was designed and developed to extract and recover elements such as Fe, Al, Na, Ti and REE. The future development direction for comprehensive utilization of red mud could include that the residual slag produced by the extraction and recovery of useful metals from red mud will be used as raw materials for the preparation of building decoration materials, catalytic support materials, adsorbents and so on.