Insight into the Mechanism of Cd2+ Removal by MgAl Layered Double Hydroxides with Different Host-Guest Interactions.

ABSTRACT

Layered double hydroxides (LDHs) have shown great potential as adsorbents for the removal of heavy metals. Nevertheless, how the host-guest interactions of LDHs affect the removal mechanism remains to be less explored. Herein, CO3 2- /NO3 - /SO4 2- /Cl- intercalated MgAl-LDHs with different host-guest interactions were fabricated and their removal mechanism for Cd2+ was investigated. The removal capacity increased in the order of MgAl-CO3 (127.3 mg/g)DFT calculations revealed that compared to the CdAl-LDHs formation the Gibbs free energy of the CdCO3 formation was lower, which made it easier to remove Cd2+ as CdCO3 on MgAl-CO3 . Conversely, isomorphic substitution of MgAl-NO3 to obtain CdAl-LDHs was a free energy reduction process.