Fabrication of ultra-thin MgAl layered double oxide by cellulose templating and its immobilization effect toward heavy metal ions: cation-exchange and deposition mechanism

Abstract

To remedy the heavy metal ion (HMI) pollution, unravel the relationship of material microstructure and removal performance and clarify relevant mechanism, magnesium-aluminum layered double oxide (MgAl-LDO) has been fabricated via a template method using cellulose. The variously performed characterizations show that ultra-thin flakes of about 5 nm are successfully accessible with the size of 50 ~ 100 nm. They are smaller than the ones prepared without the addition of cellulose. The distinctive structural feature endows the newly-synthesized LDO with large removal capacity for HMIs. Towards Cd2+, Pb2+ and Cu2+, the removal capacity reaches as high as 1422.3, 1336.8 and 1135.4 mg·g−1, respectively. Moreover, the highly achieved durability makes our LDO applicable to treating the polluted water. The mechanism of cation exchange along with deposition has been postulated. The Mg-OH moiety in the sample is found to dominate the HMI removal. The experimental findings are borne out by the first-principle density functional theory calculations on geometries, thermodynamics and electronic structures.