Effect of humic acids on physicochemical property and Cd(II) sorption of multiwalled carbon nanotubes

► Four sequentially-extracted peat humic acids (HAs) were coated on three MWNTs. ► Surface-bound HAs introduced O-containing groups and negative charges on the MWNTs. ► Surface-bound HAs greatly increased Cd(II) sorption by the MWNTs. ► The increase was a result of chemical complexation and electros...

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Bibliographic Details
Published in:Chemosphere (Oxford) 2012-11, Vol.89 (11), p.1316-1322
Main Authors: Tian, Xiaoli, Li, Tingting, Yang, Kun, Xu, Yong, Lu, Huifeng, Lin, Daohui
Format: Article
Language:English
Subjects:
adsorbents
Adsorption
Applied sciences
Biological and physicochemical phenomena
Biological and physicochemical properties of pollutants. Interaction in the soil
cadmium
Cadmium - chemistry
carbon nanotubes
Earth sciences
Earth, ocean, space
electrostatic interactions
Engineering and environment geology. Geothermics
Environmental Pollutants - chemistry
Exact sciences and technology
Heavy metal
heavy metals
humic acids
Humic Substances
metal ions
Nanomaterials
Nanotubes, Carbon - chemistry
Natural organic matter
Natural water pollution
peat soils
physicochemical properties
Pollution
Pollution, environment geology
Soil and sediments pollution
soil remediation
Sorption
surface area
Water treatment and pollution
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Summary:► Four sequentially-extracted peat humic acids (HAs) were coated on three MWNTs. ► Surface-bound HAs introduced O-containing groups and negative charges on the MWNTs. ► Surface-bound HAs greatly increased Cd(II) sorption by the MWNTs. ► The increase was a result of chemical complexation and electrostatic attraction. ► Later-extracted HA was favorable for the coating but increased less sorption. Carbon nanotubes (CNTs), as a type of superior adsorbents for both organic and inorganic contaminants, are increasingly introduced into the environment. Ubiquitous natural organic matter (NOM) would coat on the released CNTs and change their physicochemical properties and sorption of contaminants. The effects of four sequentially extracted humic acids (HAs, as a model NOM) from a peat soil on the physicochemical properties and Cd(II) sorption of three multiwalled CNTs (MWNTs) with different surface areas were investigated. The MWNTs as purchased with very few oxygen-containing functional groups had relatively low sorption capacities (0.93–1.49mgg−1) for Cd(II) and the sorption capacity increased with increasing surface area of the MWNTs. Surface-coating with the HAs lowered surface areas of the MWNTs but greatly increased their sorption capacities (5.42–18.4mgg−1). The MWNT-bound HAs introduced oxygen-containing functional groups and negative charges to the MWNT surfaces, which could thus increase the apparent sorption of Cd(II) through chemical complexation and electrostatic attraction, respectively. The later-extracted HAs with lower polarity were more favorable for the surface-coating but increased less Cd(II) sorption by the MWNTs. The results are expected to shed light on understanding the underlying mechanism of the effect of NOM on the sorption of heavy metal ions by CNTs.
ISSN:0045-6535
1879-1298
DOI:10.1016/j.chemosphere.2012.05.082