Adsorptive Removal of Radioactive Cesium from Model Nuclear Wastewater over Hydroxyl-Functionalized Mxene Ti₃C₂T_<i>x</i>

Abstract

Selective removal of 137Cs from nuclear wastewater is still a challenge due to the issues of efficient adsorbent exploitation and high concentrations of competitive ions. In this study, two-dimensional-layered Mxene Ti3C2Tx achieved the surface alkaline modification with KOH to be used as an efficient adsorbent for Cs+ removal from model wastewater. Hydroxyl-modified Ti3C2Tx obtained improved the delamination morphology and surface structure compared with the pristine Ti3C2Tx. In addition, the F species in Ti3C2Tx were efficiently removed and the hydroxyl groups were increased after modification. The adsorption efficiency of Cs+ over the hydroxyl-modified Ti3C2Tx was significantly enhanced, being attributed to the improvements in morphology, structure, and properties. 0.05 g of an optimal adsorbent achieved 90% removal of Cs+ with 5 mg·L–1 initial concentration in 50 mL of model wastewater within 5 min at ambient temperature and neutral conditions. Hydroxyl-modified Ti3C2Tx also exhibited high adsorption selectivity for Cs+ in the presence of competitive metal ions such as K+, Na+, Mg2+, and Ca2+. The mechanism study revealed that the ion exchange between [Ti–O]−H+/Cs+ mainly contributed to Cs+ adsorption, and the complexation between the oxygen-containing groups [Ti–O] in modified Ti3C2Tx and Cs was also involved. The hydroxyl-modified Ti3C2Tx was easy to regenerate and exhibited good recyclability for Cs+ adsorption.