The daily growing demand for critical materials has further highlighted the importance of secondary sources such as industrial waste streams. Waste clay, a phosphate ore process tailing, contains a remarkable amount of critical materials such as P and REEs so that comparing to different phosphate ore process streams, waste clay presents the highest concentration of REEs after phosphate rock. Due to the enormous volume of this waste accumulated in Florida to date, this reserve can satisfy a great portion of U.S. domestic demand for REEs, as an example. However, due to its troublesome nature, this reserve poses severe environmental problems along with economic loss. Two required attempts are the removal of extremely fine-sized clays, followed by the recovery of phosphate content, which can pave the path for the recovery of REE-bearing phases. Different possible remedies or combination of them have been considered by various research/ industrial trials, including froth flotation, selective-flocculation, floc-flotation, cycloning, gravity separation, magnetic separation, leaching, etc., most of which have shown no promising solution because of failing to address economic and of course environmental concerns. Moving from mostly chemical separation processes to the primarily physical/ physicochemical processes with low operational costs and environmental impacts could be a general solution. This requires detailed mineralogical and elemental characterization, physicochemical, rheological, electrochemistry, surface chemistry, crystal chemistry, solution chemistry, and quantum chemistry investigations on each single and then mixed-phase systems composing waste clay. Such insights can help develop the fundamental knowledge, upon which more versatile and efficient solutions can be established.

每天对关键材料的需求不断增长，这进一步凸显了诸如工业废物流之类的二次资源的重要性。废粘土是磷酸盐矿石工艺的尾矿，其中包含大量的关键物质，例如P和REE，因此与不同的磷酸盐矿石工艺流相比，废粘土呈现出仅次于磷酸盐岩的最高REE浓度。例如，由于迄今为止在佛罗里达州积累的大量废物，该储备可以满足美国国内对稀土的很大一部分需求。然而，由于其麻烦性质，该保护区带来了严重的环境问题以及经济损失。两项必需的尝试是去除极细粒度的粘土，然后恢复磷酸盐含量，这可以为恢复含REE的相铺平道路。各种研究/工业试验已经考虑了不同的可能补救措施或它们的组合，包括泡沫浮选，选择性絮凝，絮凝浮选，旋流，重力分离，磁力分离，浸出等，其中大多数没有显示出有希望的解决方案因为未能解决经济问题，当然也没有解决环境问题。从较低的运营成本和对环境的影响，从大部分化学分离过程转变为主要的物理/物理化学过程可能是一个通用解决方案。这要求对组成废黏土的每个单相然后混合相的系统进行详细的矿物学和元素表征，物理化学，流变学，电化学，表面化学，晶体化学，溶液化学和量子化学研究。