Novel devices for the extraction and recovery of rare-earth metals through recycling of waste

Efficient waste management practices can utilize waste as a resource for the recovery of valuable metals. Rare-earth metals have significant economic importance and are currently in high demand because of their strategic industrial applications. These metals are critical to the development of advanced devices. However, the supply of critical metals from naturally occurring ores is facing scarcity due to the technological bottlenecks, mining restrictions, and geopolitical issues. Industrial and urban waste can be a useful resource for the recovery of these metals. Since conventional methods release toxic emissions into the environment, new technologies for metal recovery from waste should be investigated. Microfluidic devices such as membranes and coiled flow inverters may be an alternative technology for waste recycling. The aim of this paper is to review the possible applications of microextraction technology for metal recovery, and to gain an insight to the metal ion transport in microfluidic devices that can provide enhanced mass-transfer rates. The relevant published literature show that device fabricated in various helical shapes with 90° bends in flow trajectory can potentially replace conventional extraction systems. Studies demonstrate that nearly six-times enhancements in separation efficiencies have been achieved with respect to the values of Sherwood number obtained for gas–liquid contact operations when coiled membrane modules replace conventional extractors. The microfluidic devices for metal recovery from waste may therefore be considered for future industrial applications.