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 andsemi-quantitative detection of trivalent terbium and europium in aqueous solution withoutsignificant process costs. The detection does not require a spectrophotometer, as theevaluation is done"on thefly"with the bare eye based on an optical signal. Sensitivedetection 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 theevaluation of an Eu3+and/or Tb3+content in real systems, such as wastewater or leachingsolutions. The detection procedure consists of an optical read-out of the luminescencesignal simultaneous to separation of various chemical species. Detection is triggered by a sensitization of the emission of the trivalentlanthanide ions during a thin-layer chromatography (TLC) process. 4 '-Phenylterperydine is present in an eluent and used as anultra-fast complexation agent functioning as highly effective photoluminescence sensitizer. The detection is done for concentrationssuitable for the lanthanide recovery with the detection limit being 0.01 mM (typical lanthanide recovery limit is 0.3 mM). The novelprocess therefore can be used for an evaluation of suitability and profitability of their extraction from a respective solution even in thepresence of various other metal ions and anions. The method developed also has potential for the detection of other luminescentrare-earth ions.