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

[Display omitted] •Novel ultra-thin (5 nm) MgAl-LDO was fabricated by the cellulose template.•High removal performance was achieved toward toxic Cd2+, Pb2+ and Cu2+.•HMI-substituted LDH and precipitate (base or salt) are recognized in product.•Mg-OH moiety of sample is unraveled to play a key role in the removal process.•Cation-exchange mechanism along with deposition is postulated by experiment and DFT. 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.