Superefficient separation of Th(IV) and U(VI) by lignin-derived magnetic biochar via competitive adsorption mechanism

Thorium (Th) and uranium (U) separation remains a huge challenge due to their high similarity in chemical behavior. In this study, lignin-derived magnetic biochar (AL-Fe/BC), which can provide functional sites for adsorbing Th(IV) and U(VI), was synthesized for the selective extraction of Th(IV) from the binary U(VI)-Th(IV) matrix. Characterizations results confirm the successful zero-valent iron loading, and the AL-Fe/BC exhibited a developed polyporous structure, high surface area, stable crystallinity, high defects degree, and advantageous magnetic feature of expedient recovery from water without energy consumption. The optimist AL-Fe/BC-800 showed an outstanding adsorption capacity with a maximal Th(IV) uptake of 2000 mg/g, and a small absorp-tion of 3 mg/g of U(VI) (Th(IV) = 180 mg/L, U(VI) = 20 mg/L, AL-Fe/BC-800 = 0.05 g/L). Moreover, the separation factor of Th(IV) from the Th(IV)-U(VI) matrix reached 90,000 even concomitant with high a con-centration of co-existing ions. The active adsorption sites on AL-Fe/BC-800, such as COOH, C-OH, C=O, pyridinic N, graphitic N, and pyrrolic N, exhibited a stronger binding affinity with Th(IV) than U(VI), achieving selective Th(IV) adsorption via a chemisorption process on the basis of competitive adsorption. In summary, AL-Fe/BC-800 is a potential adsorbent in industrial application for the superefficient separation of Th(IV) and U(VI) with high-performance magnetic recovery, promoting the sustainable development of nuclear industry, espe-cially considering the necessary development of Th(IV) fuel.