Layered double hydroxides@carbon quantum dots driven ultrafast cadmium mineralization by decoration-metal ion chelation boosted calcium vacancy

Cadmium pollution has become a globally concerning environmental issue due to its bioaccumulative propensity and potential health threats, and thus many cadmium remediation materials have been developed. However, with low cadmium concentration, partial existing remediation materials including layered double hydroxides (LDHs) show the prolonged reaction time (> 30 min) and low removal efficiency. Therefore, it is appealing to further develop ultrafast, easy-to-operate, and efficient cadmium remediation materials. In this study, we have developed an ultrafast and efficient cadmium remediation material using carbon quantum dots (CQDs) decorated calcium‑aluminum layered double hydroxides (CaAl-LDHs) via non-covalently functionalization. It is disclosed that the CQDs modification could induce the increment of calcium vacancy in LDHs layers, which reduces the cadmium adsorption energy barrier and promotes the isomorphous substitution. With such a calcium vacancy regulation strategy, the cadmium adsorption capacity showed 25.2% enhancement and the mineralization time reduced from 30 min to 30 s. This work has proposed an effective and ultrafast cadmium adsorbent by regulating the calcium vacancy and provided a promising approach to develop heavy metal remediation materials with non-covalently functionalization strategy.