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

Abstract

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 Eu 3+ and/or Tb 3+ 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.

A photoluminescence assay with a portable device for rapid, sensitive and selective detection of europium and terbium

“…Table 1 highlights the signicance of our protocol, with sensitivity over two orders of magnitude higher than other published methods for Eu 3+ . 8,[11][12][13][14][15][16][17][18][19] The luminescence behaviour of lanthanides is controlled by three types of transitions: LMCT, 4f-5d transitions, and 4f-4f transitions. 2,20 The lower energy 4f-4f transitions have low absorption coefficients (typically <3 M −1 s −1 ).…”

“…Table 1 highlights the significance of our protocol, with sensitivity over two orders of magnitude higher than other published methods for Eu 3+ . 8,11–19…”

“…Photoluminescent sensing methods have advantages for lanthanide detection due to their high sensitivity, portability, rapid measurement time, and low instrument cost. [8][9][10] Lanthanides have inherently sharp, almost line-like emission bands involving 4f-4f transitions, as the 4f orbital is effectively shielded by 5s and 5p orbitals. Consequently, element-specic emission bands make lanthanides excellent analytes for photoluminescence-based detection.…”