Journal
ENVIRONMENT INTERNATIONAL
Volume 126, Issue -, Pages 234-241Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.envint.2019.02.036
Keywords
Cadmium; gamma-Al2O3; Precipitation; Cd-Al layered double hydroxide; Cd hydroxide phases; CdCO3
Categories
Funding
- National Key Research and Development Program of China [2018YFC1800503]
- Natural Science Foundation of Jiangsu Province, China [BE2018760]
- National Natural Science Foundation of China [41771276]
- 135 Frontier Projects of Institute of Soil Science, Chinese Academy of Sciences [ISSASIP1619]
Ask authors/readers for more resources
Apart from surface complexation, precipitation of minerals also plays an important role in reducing the mobility and transport of heavy metals in the environment. In this study, Cd(II) sorption species on surfaces of gamma-Al2O3 at pH 7.5 were characterized using multiple techniques. Results show that in addition to adsorption complexes, Cd hydroxide phases (Cd(OH)(2) precipitates and Cd-x(OH)(y) polynuclear complexes) were formed at the initial stages of Cd(II) sorption and gradually transformed to CdCO3 with time. In addition, Cd(II) formed Cd-Al layered double hydroxide (LDH) on gamma-Al2O3 under various conditions, independent of temperature and Cd loadings. The formation of Cd hydroxide phases and Cd-Al LDH could be ascribed to surface-induced precipitation because the bulk solution was undersaturated with respect to hydroxides. Cd-Al LDH formation on the Al-bearing mineral here is rather surprising because typically this occurs with elements of ionic radii similar to that of Al3+; this formation is unknown for metals such as Cd(II) with a much larger ionic radius. The thermodynamic feasibility of Cd-Al LDH formation was further confirmed by laboratory synthesis of Cd-Al LDH and density function theory (DFT) calculations. These results suggest that Cd precipitation on Al-bearing minerals can be an important mechanism for Cd immobilization in the natural environment. Additionally, the finding of Cd-Al LDH formation on Al-bearing minerals and the thermodynamic stability of Cd-Al LDH provides new insights into the remediation of Cd-polluted soils and aquatic systems.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available