Rare earth elements (REEs) are a series of chemical elements found in the Earth’s crust. Due to their unique chemical properties, REEs have become essential components of many technologies spanning a range of applications, including electronics, computer and communication systems, transportation, health care, and national defense. REEs are considered rare because they are found in relatively low concentrations and require further processing, which is technically and economically challenging. Control of the world’s operating REE mines is heavily consolidated which has resulted market insecurities. However, the demand for REEs continues to grow, creating a need for economically feasible approaches for REE recovery from nontraditional sources. New methods of recovery must be developed that can rapidly, accurately, and economically screen coal waste streams for high concentrations of REEs that would be suitable for separation and recycling.

This invention describes a portable luminescence-based fiber optic sensor for the detection and quantification of REEs in coal by-product waste streams. The device provides rapid results, with a lower limit of detection in the parts per-billion, for terbium, europium, dysprosium, and samarium. The device can be used with luminescence sensitizers to lower the limit of detection for the quantification of additional REEs. The rapid response time provided by the device can save the end user costs associated with inactivity during recovery or mining operations while potentially allowing for in line monitoring or rapid field sampling. Compared to conventionally used technology such as inductively coupled plasma-mass spectrometry, the novel sensor represents a more affordable, compact, and field ready option for REE detection.