Self-Assembled Bolaamphiphile-Based Organic Nanotubes as Efficient Cu(II) Ion Adsorbents
- Kansas State University, Manhattan, KS (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
- Kansas State University, Manhattan, KS (United States)
- Argonne National Laboratory (ANL), Argonne, IL (United States)
Self-assembled organic nanotubes (ONTs) have been actively examined for various applications such as chemical separations and catalysis owing to their well-defined tubular nanostructures with distinct chemical environments at the wall and internal/external surfaces. Adsorption of heavy metal ions onto ONTs plays an essential role in many of these applications, but it has rarely been assessed quantitatively. Herein, we investigated interactions between Cu2+ and single-/quadruple-wall bolaamphiphile-based ONTs having inner carboxyl groups with different inner diameters, COOH-ONT10nm and COOH-ONT20nm. We first examined the effects of Cu2+ on their nanotubular structures using SAXS, STEM, and AFM. COOH-ONT10nm was stable in aqueous Cu2+ solution in contrast to COOH-ONT20nm owing to the presence of polyglycine-II-type hydrogen bonding networks within its wall. Subsequently, we studied the Cu2+ adsorption behavior of COOH-ONT10nm by monitoring the concentration of unbound Cu2+ using linear sweep anodic stripping voltammetry. The Cu2+ adsorption was quick, attributable to efficient Cu2+ partitioning through the open ends of the ONT, followed by fast Cu2+ diffusion in the uniform, relatively large nanochannel. More importantly, the Cu2+ adsorption capacity and affinity of COOH-ONT10nm were measured at different pH using the Langmuir adsorption model. The adsorption capacity was similar at the pH range examined, showing the participation of approximately 25% of the inner carboxyl groups in the adsorption. The adsorption affinity increased with pH, indicating the essential role of the deprotonated carboxyl groups in the Cu2+ adsorption. Most interestingly, the Langmuir adsorption constant was significantly higher than those of previously reported synthetic adsorbents and planar monolayer based on carboxyl binding sites. The high Cu2+ affinity of the ONT was attributable to the highly dense binding sites on the well-defined nanoscale concave structure of the inner channel. Furthermore, these results provide a valuable guideline to designing self-assembled nanomaterials for efficient chemical separations, detection, and catalysis.
- Research Organization:
- Kansas State Univ., Manhattan, KS (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
- Grant/Contract Number:
- SC0002362; AC02-06CH11357
- OSTI ID:
- 2484139
- Journal Information:
- Langmuir, Vol. 40, Issue 52; ISSN 0743-7463
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Organic nanotube
Bolaamphiphile
Copper (II) ion
Small-angle X-ray scattering
Polyglycine-II-type hydrogen bonding
Voltammetry
Langmuir adsorption model
Adsorption
Carboxyls
Hollow structures
Solution chemistry
X-ray scattering