Rapid Spectrometer-Free Luminescence-Based Detection of Tb3+ and Eu3+ in Aqueous Solution for Recovery and Urban Mining

A novel and robust procedure was developed for the rapid qualitative and semi-quantitative detection of trivalent terbium and europium in aqueous solution without significant process costs. The detection does not require a spectrophotometer, as the evaluation is done "on the fly" with the bare eye based on an optical signal. Sensitive detection is even possible in acidic solution and the presence of heavy metal ions. Therefore, the method presented can be used for an urban mining approach for the evaluation of an Eu3+ and/or Tb3+ content in real systems, such as wastewater or leaching solutions. The detection procedure consists of an optical read-out of the luminescence signal simultaneous to separation of various chemical species. Detection is triggered by a sensitization of the emission of the trivalent lanthanide ions during a thin-layer chromatography (TLC) process. 4′-Phenylterperydine is present in an eluent and used as an ultra-fast complexation agent functioning as highly effective photoluminescence sensitizer. The detection is done for concentrations suitable for the lanthanide recovery with the detection limit being 0.01 mM (typical lanthanide recovery limit is 0.3 mM). The novel process therefore can be used for an evaluation of suitability and profitability of their extraction from a respective solution even in the presence of various other metal ions and anions. The method developed also has potential for the detection of other luminescent rare-earth ions.