Treatment of heavy metal ions in wastewater using layered double hydroxides: A review

ABSTRACT

Heavy metal ions are toxic, and their toxicities change with different valence states, charges, and radii. Among the methods used for heavy metal ion removal, adsorption is widely employed due to its low cost and simple operation. As natural anionic clays, layered double hydroxides (LDHs) have drawn considerable attention for their use in the removal of anionic pollutants (such as heavy metal anions) due to their high removal efficiency and environmental friendliness. This article reviews the effects of the charge, type, and radius of the cations in the laminates of LDHs and the anions in the LDH interlayers, as well as the charge and radius of the heavy metals and the conditions (such as pH, coexisting ions, and temperature) on removing heavy metal ions with LDHs. The removal mechanisms have also been discussed. LDHs are hugely promising as an application for removing heavy metal ions that exist in different ionic forms by controlling the type and condition of LDHs.

GRAPHICAL ABSTRACT

KEYWORDS:

• Adsorption
• anions exchange
• heavy metal ions
• layered double hydroxides

Additional information

Funding

National Natural Science Foundation of China [grant number 51374157], [grant number 51504170]; Program for New Century Excellent Talents in University [grant number NCET-12-0713]; Nature Science Foundation of Hubei Province of China [grant number 2013CFA106], [grant number 2015CFB506]; and Postgraduate Education and Innovation Foundation of Wuhan Institute of Technology [grant number CX2016180].