Efficient removal of trace thallium from NH4ReO4 solutions using titanium dioxide nanofibers

A highly effective, stable, and recyclable adsorbent based on titanium dioxide nanofibers (TNFs) was fabricated via a one-step hydrothermal synthesis. The application of TNFs for the deep removal of thallium (Tl) from ammonium perrhenate (NH4ReO4) solutions was investigated. The effect of different factors, including hydrothermal temperature and time (120–170 °C, 4–10 h), adsorbent surface area (3–12 cm2), initial concentration of Tl(III) (2–10 mg/L) and pH (2–10) on the removal performance, was analyzed using batch adsorption experiments. Kinetic analysis revealed that the removal process followed a pseudo-first-order model. The adsorption data of TNFs were analyzed using Freundlich and Langmuir isotherms, with the Langmuir isotherm showing the best fit and indicating a theoretical maximum adsorption capacity of 767.2 mg m−2. Thermodynamic studies demonstrated the adsorption process was characterized by physisorption, being spontaneous, and exothermic. Under optimized conditions, TNFs demonstrated successful removal of Tl(III) from NH4ReO4 solutions with limited adsorption of rhenium (Re) and arsenic (As) ions. Acidity and reusability tests confirmed the significant stability and excellent recoverability of TNFs. The proposed TNFs serve as an effective, and stable adsorbent with a high affinity for Tl(III), offering a viable and efficient approach for the purification of NH4ReO4 solutions.