Abstract
Adsorption of Hg2+ and methylmercury (MeHg) to multi-walled carbon nanotubes (MWCNTs) modified, respectively, with hydroxyl, amine and carboxyl groups was studied. The effect of various factors like the initial pH, natural organic matter (NOM), Cl- and adsorbent dose on the sorption efficiency were evaluated. It was found that amine-modified MWCNTs showed a strong adsorption capacity to Hg2+ and MeHg, and the removal efficiency could reach up to 92% (0.5 g/L MWCNTs, and 100 μg/L Hg2+ and MeHg) which is independent of pH. NOM had complex effects on the adsorption of Hg2+ and MeHg to MWCNTs. Cl- inhibited the adsorption of Hg2+ and MeHg to MWCNTs. The adsorption of Hg2+ and MeHg was found to be inhomogeneous and homogeneous chemisorption, respectively. Our results suggested that MWCNTs modified with different functional groups can efficiently adsorb both Hg2+ and MeHg in aqueous environment.
Highlights
Because of its long distance migration and bioaccumulation, mercury as a global pollutant has been attracting widespread attention [1,2]
We studied the removal efficiency of Hg2+ and MeHg from aqueous solution by pristine multi-walled carbon nanotubes (MWCNTs) and MWCNTs modified with carboxylic functional group (MWCNTs-COOH), hydroxyl functional group (MWCNTs-OH), and amino functional group (MWCNTs-NH2), respectively
While no major functional group was identified for the pristine MWCNTs, symmetric and asymmetric methylene stretching bands appeared at ~2962 and ~2884 cm−1 were detected in functionalized MWCNTs
Summary
Because of its long distance migration and bioaccumulation, mercury as a global pollutant has been attracting widespread attention [1,2]. Mercury in environment and biological body mainly exists in three forms including Hg0, Hg2+ and methylmercury (MeHg). MeHg is the most toxic organic mercury and is ubiquitous in the aquatic environment [7]. Mercury pollution comes mainly from industrial production, mercury mine and non-ferrous metals processing factory [8]. Various kinds of methods have been used to remove heavy metals from aqueous solutions including ion exchange, chemical precipitation, biological treatment, membrane filtration and adsorption [9]. Carbon nanotubes (CNTs), as adsorbents in the field of environment, have attracted more and more attention, because of their unique structure and chemical properties [10,11,12]
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