Construction of polydopamine-functionalized phosphate-intercalated Mg-Fe layered double hydroxide for efficient removal of U(VI)

Polydopamine-coated phosphate-intercalated Mg-Fe layered double hydroxides (PDA/phos-LDH) were fabricated to capture U(VI). Phosphate was intercalated in the layers of LDH because of its strong affinity for U(VI) species and the PDA was employed to provide massive binding sites for U(VI) by promoting the dispersion of LDH in the matrix. Experimental results revealed that the introduction of phosphate and PDA significantly increased the removal amount for U(VI) because of the increased functional groups (including PO43- , -OH, -NH2 and aromatic ring). The highest removal amount of PDA/phos-LDH (pH = 3.0, T = 298 K) reached 912.0 mg/g within 60 min, which was higher than many other LDH-based adsorption materials. After 5 repeated uses, the uptake percentage was still as high as 81.4 %. In addition, the excellent dynamic adsorption performance further confirmed the potential of PDA/phos-LDH in the actual processing of U(VI)-containing wastewater. Ion exchange, complexation, electrostatic attraction, cation-& pi; interaction and precipitation were confirmed to play prominent roles in U(VI) removal. In a word, PDA/phos-LDH was an exceptional adsorbent for U(VI) immobilization.