Selective Tl(I) Removal by Prussian Blue–Zero Valent Iron Nanoparticles

Thallium (Tl) is a trace metal with high toxicity and exists in the aquatic environment as Tl(III) and Tl(I). Tl(I) is a major species in industrial wastewater and natural water, which has high solubility, stability, and mobility and is difficult to remove. In this study, Prussian blue–zerovalent iron nanoparticles (PB-nZVI) were successfully prepared at room temperature. The performance of PB-nZVI in removing Tl(I) was studied and compared with PB and nZVI. The experimental results showed that PB-nZVI can remove Tl(I) efficiently (>97%) in a pH range of 3–9, while the highest removal rates of PB and nZVI for Tl(I) were only 83.8% and 53.1% (pH = 9), respectively. Additionally, the variation of Tl(I) removal efficiency in different relative parameters has been studied, such as Tl(I) initial concentration, dosage of absorbent materials, and coexisting cations (K⁺, Ni²⁺, Pb²⁺, Zn²⁺, Ca²⁺, Mg²⁺, Cd²⁺, and Cu²⁺). PB-nZVI showed extremely high selectivity for Tl(I), and the efficiency of Tl(I) removal was slightly affected by the coexisting cations with 100 and 1000 mg/L. However, the Tl(I) removal by PB and nZVI was significantly inhibited under identical conditions. The involved mechanisms are as follows: adsorption, precipitation, and ion exchange. The synergistic effect of PB and nZVI enables PB-nZVI to efficiently remove thallium from wastewater.