Jump to main content
Jump to site search


Surface Defect Enhances the Adsorption Affinity and Selectivity of Mg(OH)2 towards As(V) and Cr(VI) Oxyanions: A Combined Theoretical and Experimental Study

Abstract

The surface defects of adsorbents are generally considered to be the active sites for adsorbates, and the adsorption behaviors of a variety of pollutants in wastewater are strongly influenced by the surface defects of adsorbents. With simple chemical and structural properties, nano-Mg(OH)2 exhibits a high adsorption affinity and selectivity to heavy metals from wastewater, and the insight into the surface complex structures of heavy metals on the Mg(OH)2 surface is fundamental for both the mechanism and application of defective adsorbents in wastewater treatment. In this study, the impact of surface defects of Mg(OH)2 nanoplates on the structure, energy, and adsorption kinetics of toxic heavy metal oxyanions (HAsO42- and CrO42-) is investigated by combining the first-principles calculations and batch experiments. The first-principles calculations illustrated that the heavy metal oxyanions can steadily incorporate into the surface defects forming inner-sphere complexes. The incorporated heavy metal oxyanions have strong charge-charge and chemical bonding interactions with the surface defect sites, much stronger than the hydrogen bonding interaction with the surface OH sites. Besides, the adsorption affinity of surface defects towards heavy metal oxyanions is stronger than the other oxyanions (e.g. SO42- and NO3-), indicating the high adsorption selectivity of heavy metal oxyanions over other oxyanions. The batch adsorption experiments verified that the adsorption of defect-rich Mg(OH)2 adsorbents towards heavy metal ions, e.g. As(V) and Cr(VI), is favorable even under the condition of low concentration (mg/L level). These findings reveal the significance of surface defects of Mg(OH)2 in extracting As(V) and Cr(VI) from low concentration solutions. The proposed strategy of surface defect fabrication should provide a useful insight into designing effective adsorbents for the selective extraction of heavy metal oxyanions at low concentration.

Back to tab navigation

Supplementary files

Publication details

The article was received on 17 Jun 2018, accepted on 09 Oct 2018 and first published on 10 Oct 2018


Article type: Paper
DOI: 10.1039/C8EN00654G
Citation: Environ. Sci.: Nano, 2018, Accepted Manuscript
  •   Request permissions

    Surface Defect Enhances the Adsorption Affinity and Selectivity of Mg(OH)2 towards As(V) and Cr(VI) Oxyanions: A Combined Theoretical and Experimental Study

    X. Ou, X. Liu, W. Liu, W. Rong, J. Li and Z. Lin, Environ. Sci.: Nano, 2018, Accepted Manuscript , DOI: 10.1039/C8EN00654G

Search articles by author

Spotlight

Advertisements