One-pot synthesis of magnetic Prussian blue for the highly selective removal of thallium(I) from wastewater: Mechanism and implications

Thallium (Tl) often enters the environment via mineral exploitation and utilization. The main restriction of Tl removal is the interference of high concentrations of coexisting ions in wastewater, therefore, enhancing the selectivity for Tl is essential to its treatment. Magnetic Prussian blue particles (Fe3O4@PB), an ion-sieving ma-terial with an open structure, were synthesized through a "one-pot" method at room temperature for the highly selective removal of Tl+. The removal percentage of Tl+ was over 92% even when the concentration of coexisting ions (e.g. Zn2+, Cd2+, Cu2+, and Pb2+) were 10,000 times higher than the initial concentration of Tl+. The maximal experimental removal capacity was 528 mg Tl/g Fe3O4@PB, and the removal percentage remained steady at pH 3-10. The high selectivity of Fe3O4@PB for Tl+ is attributed to the fact that hydrated Tl+ has a smaller hydrated diameter and a lower hydration free energy than other coexisting ions, while the rapid adsorption kinetics of Tl+ results from the negative surface charge and the network of nanocapillaries of the Fe3O4@PB. Overall, a new low-cost material that is easy to synthesize and has superior Tl+ removal capacity with extremely high selectivity for Tl+ was obtained for effective magnetic removal of thallium from wastewater.