Effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes: Relationship with NOM properties

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2012-08, Vol.200-202, p.627-636
• Main Authors: Sun, Wei-Ling, Xia, Jing, Li, Si, Sun, Fang
• Format: Article
• Language: English
• Subjects: Absorbance; Adsorption; Applied sciences; carbon; Carbon content; carbon nanotubes; Chemical engineering; Correlation; Cu(II); Exact sciences and technology; Fluorescence; heavy metals; hydrophobic bonding; Multi wall carbon nanotubes; Multi-walled carbon nanotubes; Natural organic matter; organic matter; oxygen; sorption isotherms; Spectra; X-ray photoelectron spectroscopy
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2012.06.118

► Effect of NOM characteristics on the Cu adsorption by MWCNTs was investigated. ► Cu adsorption by MWCNTs increased with increasing NOM concentration. ► The aromaticity is a key factor for NOM sorption on MWCNTs. ► O-containing functional groups play critical roles in NOM effect on Cu adsorption. The effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes (MWCNTs) was investigated. Particular attention was paid to the relationship between NOM properties and NOM adsorption and their effects on the Cu(II) adsorption by MWCNTs. The results showed that the NOM adsorption data were well fit to the Freundlich isotherm model, and the MWCNTs that had higher oxygen content had lower KF (Freundlich constants) values. The KF values for the different types of NOM varied greatly and were proportional to the aromatic carbon content, the specific ultraviolet absorbance at 275nm, and the TOC-normalized fluorescence intensity of the F3 peak at ∼460nm. In contrast, they had negative linear correlations with the absorbance ratios at 250nm and 365nm and the TOC-normalized fluorescence intensity of the F1 peak from 250nm to 300nm. The results indicated that π–π and hydrophobic interactions were the predominant NOM adsorption mechanisms by the MWCNTs. The Cu(II) adsorption by the MWCNTs increased with increasing NOM concentrations due to the complexing of Cu(II) with the adsorbed NOM. This was confirmed by XPS and FTIR spectra. The increased degree of Cu(II) adsorption was positively correlated with the carboxyl carbon content, carboxyl group content, and the polarity index of the NOM. The findings in this study highlight that the NOM characteristics are responsible for controlling the NOM adsorption and its effects on heavy metal sorption by MWCNTs.