Modeling Uranyl Adsorption on MoS2/Mo2CT x Heterostructures Using DFT and BOMD Methods

Uranyl ions prefer to be adsorbed atdeprotonated O siteson the Mo2COH surface and S sites on the MoS2 side of the MoS2/Mo2CT (x) heterojunctions. More importantly, the oxidation stateU-(VI) can be reduced to U-(V) and then to U-(IV) caused by the strongreducibility of the Mo2COH surface at room temperature,whereas the uranyl complex can move freely on the MoS2 surface. Uranium-bearingwastewaters exert a great threat to the ecologicalenvironment due to its high radiotoxicity level. The designing andfabrication of novel adsorption materials can be promoted for radionuclideelimination from wastewater. In this work, results from density functionaltheory and Born-Oppenheimer molecular dynamics simulationsare reported for the uranyl adsorption behavior on the MoS2/Mo2CT (x) heterostructure inthe gas phase and in an aqueous environment. Uranyl ions prefer tobe adsorbed at deprotonated O sites on the Mo2COH surfaceand S sites on the MoS2 side of the heterojunctions, resultingin the formation of bidentate configurations. In addition to coordinationinteraction, H-bond and van der Waals interactions can also play animportant role in binding configurations. More importantly, the oxidationstate U-(VI) can be reduced to U-(V) and then to U-(IV) caused by thestrong reducibility of the Mo2COH surface at room temperature,whereas the uranyl complex can move freely on the MoS2 surface.However, the coordination number of U with respect to H2O in the first hydration shell on the Mo2COH surface remainsunchanged and is found to be 3, which is similar to that on the MoS2 surface. This work provides novel nanosorbents for the removalof uranyl from wastewater. The present viewpoint provides valuablemechanistic interpretations for uranyl adsorption and will give asupplement to the experimental research.

Automated summary

This study shows that uranyl ions prefer to be adsorbed at deprotonated O sites on the Mo2COH surface and S sites on the MoS2 side of the MoS2/Mo2CT(x) heterojunctions, resulting in the formation of bidentate configurations. In addition to coordination interaction, H-bond and van der Waals interactions also play an important role in binding configurations. Moreover, the oxidation state U-(VI) can be reduced to U-(V) and then to U-(IV) due to the strong reducibility of the Mo2COH surface at room temperature, while the uranyl complex can move freely on the MoS2 surface. This research provides novel nanosorbents for uranyl removal from wastewater and valuable mechanistic interpretations for uranyl adsorption.