Leaching process for terbium recovery from linear tube fluorescent lamps: optimization by response surface methodology

Abstract

Until now, rare earth elements (REEs) recycled from the green phosphor of waste fluorescent lamps (FLs), essentially terbium, remain a major challenge. The sulfuric acid effect on leaching efficiency of REEs from phosphor powder (PP) is investigated in this paper. According to a composite central design, experimental leaching study is performed under various parameters (acid concentration, leaching temperature, and time as well as liquid-to-solid ratio (L/S)). A statistical model of experiments and an analysis of variance are studied in order to predict leaching process. The results showed that by decreasing concentration and L/S ratio while increasing leaching time at optimal temperature value permits profitable terbium extraction. Afterwards, the developed statistical model is explored for an optimized response surface methodology. The obtained results were tested experimentally and showed best terbium extraction with 75%. Moreover, 0.01% for the major contaminant, that is calcium, is reached. This low calcium yield may have a further advantage during REE recovery in the downstream. Therefore, resulting solution under optimal conditions is treated with oxalic acid followed by a calcination of the solid precipitate. Finally, 43.57% and 49.38% are produced for terbium and yttrium oxides, respectively.

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

“…Responsiveness of the Ln 3+ detection method under high acidity is critical, as common mineral acids (H 2 SO 4 , HNO 3 , HCl) of concentrations 0.1−5 M are used to leach rare earth metals from waste, 16,22,28,43,44 such as used fluorescent lamps and cathode-ray tubes. 21,22,43,44 Additionally, as a result of an acidic treatment, not only cations of rare earth element ions are present in the final leaching solution but also ions of other metals such as aluminum, iron, copper, indium, and zinc. 17,44,45 As a result of our previous studies concerning interactions of the trivalent rare earth metal ions with different pyridyl-based ligands, we selected 4′-phenylterpyridine (ptpy) as a sensitizer ligand for the detection of Ln 3+ .…”

“…Recovery of lanthanide ions such as Nd 3+ can be achieved, e.g., from isolated components, such as Fe/Nd/B magnets. − In addition, significant concentrations of various lanthanide ions can be found in mining and wastewaters. ,− Trivalent lanthanide recovery of Eu 3+ and Tb 3+ are typically studied at concentrations of 0.3–5 mM (50–800 mg·L –1 ). − Examples for higher concentrations (5–50 mM, 0.8–7.5 g·L –1 ) are reported as well. − Trace concentrations (0.03–0.06 mM, 5–8 mg·L –1 ) of lanthanides such as the expensive terbium are also the subject of several recovery studies. − Generally, recovery dwindles as concentrations decrease. As of today, recovery is not possible by the majority of methods below a threshold concentration of trivalent lanthanides, which is estimated to be approximately <5 μM (<0.1 mg·L –1 ).…”

“…Responsiveness of the Ln 3+ detection method under high acidity is critical, as common mineral acids (H 2 SO 4 , HNO 3 , HCl) of concentrations 0.1–5 M are used to leach rare earth metals from waste, ,,,, such as used fluorescent lamps and cathode-ray tubes. ,,, Additionally, as a result of an acidic treatment, not only cations of rare earth element ions are present in the final leaching solution but also ions of other metals such as aluminum, iron, copper, indium, and zinc. ,, …”