PDF(Pubmed)
Abstract：
The excessive exploitation of rare earth elements (REEs) has caused major losses of non-renewable resources and damage to the ecosystem. The processes of mining and smelting produce massive amounts of wastewater with low concentrations of REEs. Consequently, the enrichment and recovery of low-concentration REEs from wastewater has significant economic and environmental value. For this purpose, operation under large phase ratios (the flow rate ratio between the aqueous phase and extractant) is more desirable and economically viable. However, the traditional REE extraction process suffers from the uneven dispersion of the extractant and the difficulty of phase separation, which leads to long extraction times and large consumption of extractants. Hence, there is an urgent need to develop a green and efficient technique to extract low concentrations of REEs from wastewater. In this work, a droplet-based microfluidic technique was used to continuously extract and recover low-concentration REEs at large phase ratios. Snowman-shaped magnetic Janus nanoparticles were added to the continuous phase as emulsifiers to facilitate uniform extractant dispersion and rapid phase separation. Several key factors affecting the extraction efficiency, including pH, residence time, and the amount of added Janus nanoparticles, were systematically investigated. Compared to batch extraction, droplet-based microfluidic extraction with the addition of Janus nanoparticles showed the advantages of a large specific surface area and fast phase separation during extraction. Meanwhile, the Janus nanoparticles exhibited good emulsification performance after three extraction cycles. In summary, the Janus nanoparticle-stabilized droplet generated by microfluidic methods provides a feasible path for the efficient enrichment and recovery of low-concentration REEs.
摘要：
稀土元素（REE）的过度开发造成了不可再生资源的重大损失和生态系统的破坏。采矿和冶炼过程会产生大量的废水，稀土元素浓度较低。因此,从废水中富集和回收低浓度稀土具有重要的经济和环境价值。为此,在大的相比(水相和萃取剂之间的流速比)下操作是更理想的和经济上可行的。然而,传统的稀土萃取工艺存在萃取剂分散不均匀、相分离困难等问题,这导致提取时间长和提取剂的大量消耗。因此，迫切需要开发一种绿色高效的技术来从废水中提取低浓度的稀土元素。在这项工作中,基于液滴的微流控技术用于在大的相比下连续提取和回收低浓度的REE。将雪人形磁性Janus纳米颗粒作为乳化剂添加到连续相中，以促进均匀的萃取剂分散和快速的相分离。影响提取效率的几个关键因素,包括pH值,停留时间,和添加的Janus纳米粒子的量，进行了系统的调查。与分批提取相比，添加Janus纳米颗粒的基于液滴的微流体萃取显示出在萃取过程中具有较大的比表面积和快速的相分离的优点。同时,在三个提取循环后,Janus纳米颗粒表现出良好的乳化性能。总之,通过微流体方法产生的Janus纳米颗粒稳定的液滴为有效富集和回收低浓度REE提供了可行的途径。
