Performance and mechanism of removing thallium from rare earth mine tailwater using MnO4−-intercalated MgAl layered double hydroxide

Efficient removal of trace thallium (Tl) from rare-earth mine tailwater remains challenging because conventional precipitation and monofunctional adsorption often provide insufficient purification and may cause secondary metal release. Herein, a permanganate-intercalated Mg Al layered double hydroxide (LDH-MnO 4 ) was synthesized via a calcination-reconstruction strategy. The material reached removal equilibrium within 30 min and exhibited a Langmuir-derived maximum Tl uptake capacity of 426.99 mg/g. The combined XPS, XRD, TEM, Raman, and Mn K-edge XAFS analyses indicated a removal mechanism that was dominated by interlayer-confined oxidation-precipitation and supplemented by surface complexation. Interlayer MnO 4 − promoted Tl(I) oxidation to Tl(III) and was converted into lower-valence MnO x species. LDH-MnO 4 maintained high Tl(I) removal efficiency over pH 5–7 and achieved 99.59% removal from actual rare-earth mine tailwater containing 6.87 μg/L Tl at a dosage of 50 mg/L. Meanwhile, the dissolved Mn concentration showed a net decrease from 3.60 to 0.35 mg/L under the tested tailwater conditions. The preliminary direct-reagent cost was estimated at 1.51 CNY/m 3 under the tested conditions, supporting further evaluation of LDH-MnO 4 for trace Tl removal from rare-earth mine tailwater.