Efficient and Superstable Mineralization of Toxic Cd<sup>2+</sup> Ions through Defect Engineering in Layered Double Hydroxide Nanosheets
Wenbo Xiong, Jikang Wang, Xianggui Kong, Geoffrey I. N. Waterhouse, Huijie Liu, Ye Wang, Shihua Liu, Ya‐Wen Wang, Shaoquan Li, Yufei Zhao, Haohong Duan
Abstract
Water and soil pollution caused by toxic cadmium ions (Cd 2+ ) is a serious threat to animals, plants, and human health. Discovering low-cost mineralizers which can efficiently and stably immobilize Cd 2+ ions is therefore imperative for wastewater treatment and soil remediation. In this work, we report the successful development of a novel mineralizer for Cd 2+ ion capture. A magnesium–aluminum layered double hydroxide (MgAl-LDH) with a monolayer structure (MgAl-mono) was first prepared and then calcined at 350 °C for 4 h to produce a defective MgAl-mono-350. MgAl-mono-350 offered a very high Cd 2+ removal capacity (1385.5 mg/g at 25 °C) and the ability to reduce the concentration of Cd 2+ in aqueous solution from 100 ppm to less than 50 ppb in 15 min (meeting the discharge standard of industrial wastewater). Detailed characterization and computational studies revealed that MgAl-mono-350 possessed abundant oxygen defects, thereby enabling superstable mineralization of Cd 2+ via isomorphous substitution process,and the Cd 2+ ions are immobilized in the generated CdAl-LDH structure. MgAl-mono-350 also offered outstanding selectivity for Cd 2+ ions over other common ions. This work demonstrates the potential of defect-engineered LDH materials for the selective removal of heavy metals from polluted water.