Preparation of diethylenetriamine-functionalized thiosulfate intercalated ZnNiAl-LDHs and its removal behavior and mechanism of U(VI)

• A novel composite adsorbent (DETA-ZnNiAl-S 2 O 3 2- -LDHs) was synthesized. • DETA-ZnNiAl-S 2 O 3 2- -LDHs showed excellent removal performance for U(VI). • The mechanism of action of U(VI) with adsorbents includes adsorption and reduction. A new composite material, diethylenetriamine-functionalized thiosulfate intercalated zinc-nickel-aluminum hydrotalcite (DETA-ZnNiAl-S 2 O 3 2- -LDHs), was synthesized by introducing S 2 O 3 2- between ZnNiAl-LDHs layers and grafting diethylenetriamine for functionalization modification. The morphological structure and physicochemical properties of samples were analyzed using XRD, FTIR, SEM and BET characterization. By analyzing the results of the batch removal experiments, it was found that the removal process of U(VI) by DETA-ZnNiAl-S 2 O 3 2- -LDHs was more consistent with the pseudo-second-order and Langmuir isotherm models, and the process was endothermic and spontaneous. The maximum removal capacity of DETA-ZnNiAl-S 2 O 3 2- -LDHs reached 558.66 mg/g at pH of 6, contact time of 6 h, sample dosage of 0.004 g and temperature of 313 K. The removal of U(VI) by DETA-ZnNiAl-S 2 O 3 2- -LDHs involved adsorption and reduction: U(VI) bound to the laminar hydroxyl group and diethylenetriamine of the material through surface complexation, while the thiosulfate in the material reduced U(VI) to U(IV) and then removed it. In addition, DETA-ZnNiAl-S 2 O 3 2- -LDHs still showed superior removal performance under high salinity and complex co-existing ion environment. The results suggest that DETA-ZnNiAl-S 2 O 3 2- -LDHs have potential applications in the efficient remediation of radioactive wastewater.