Ultrafast and Highly Selective Sequestration of Radioactive Barium Ions by a Layered Thiostannate

As a simulant of hazardous ²²⁶Ra²⁺, the simultaneously selective and rapid elimination of radioactive ¹³³Ba²⁺ ions from geothermal water is necessary but still challenging. In this paper, we demonstrated the usability of a layered thiostannate with facile synthesis and inexpensive cost, namely, K₂Sn_4-S_8- (KTS-3, x = 0.65-1), for the remediation of radioactive ¹³³Ba²⁺ in multiple conditions, including sorption isotherm, kinetics, and the influences of competitive inorganic/organic ions, pH values, and dosages. KTS-3 has a strong barium uptake ability (171.3 mg/g) and an ultrafast adsorption kinetics (about 2 min). Impressively, it can achieve a high preference for barium regardless of the excessive interference ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, and humic acid) and acidic/alkaline environments, with the largest distribution coefficient K_d value reaching 6.89 × 10⁵ mL/g. Also, the Ba²⁺-laden products can be easily eluted by a concentrated KCl solution, and its adsorption performances for barium resist well even after five consecutive cycles. In addition, owing to the regular appearance and excellent mechanical strength, the prepared KTS-3/PAN (PAN = polyacrylonitrile) granule displays a good removal efficiency in the flowing ion-exchange column. These advantages mentioned above render it very promising for the effective and efficient cleanup of radioactive ¹³³Ba²⁺-contaminated wastewater.