Highly efficient removal of aqueous Cu(II) and Cd(II) by hydrothermal synthesized CaAl-layered double hydroxide

Adsorbents with a large adsorption capacity and rapid removal rate are required for wastewater treatment containing heavy metal ions. Thus, CaAl-layered double hydroxide (CaAl-LDH) was successfully fabricated by a simple hydrothermal method as an efficacious sorbent to capture Cu(II) and Cd(II) ions in water. The as-synthesized CaAl-LDH exhibited the representative peaks of an LDH, good crystallinity, and a hexagonal lamellar structure. The entire adsorption process of CaAl-LDH for aqueous Cu(II) and Cd(II) was highly efficient and fast. The theoretical maximum removal capacities of CaAl-LDH for Cd(II) and Cu(II) were 1035.4 and 381.9 mg/g, respectively. Cu(II) and Cd(II) ions were adsorbed quickly in the first 60 min, and the kinetics data were generally consistent with a pseudo-second-order model. CaAl-LDH had a large distribution coefficient for Cd(II) (7.55 ×105 mL/g) and Cu(II) (4.78 ×105 mL/g). The possible mechanisms were precipitation, isomorphic substitution, and surface complexation. The results of this study demonstrate the potential applicability of CaAl-LDH for adsorption of heavy metals from aqueous solution.