Striking analogies and dissimilarities between graphene oxides and humic acids pH-dependent charging and colloidal stability /
This study provides a comparative framework on the elucidation of analogies and differences in the interfacial protolytic processes and the associated colloidal behaviour of a typical humic acid (HA) and a set of single-layer graphene oxide (SLGO) and (multi-layered) graphite oxide samples in aqueou...
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| Format: | Article |
| Published: |
2020
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| Series: | JOURNAL OF MOLECULAR LIQUIDS
306 |
| doi: | 10.1016/j.molliq.2020.112948 |
| mtmt: | 31274258 |
| Online Access: | http://publicatio.bibl.u-szeged.hu/20665 |
| Summary: | This study provides a comparative framework on the elucidation of analogies and differences in the interfacial protolytic processes and the associated colloidal behaviour of a typical humic acid (HA) and a set of single-layer graphene oxide (SLGO) and (multi-layered) graphite oxide samples in aqueous electrolyte media. The pH dependence of the surface charge densities of HA and SLGO was explored at three different salt concentrations by potentiometric acid-base titration, along with simultaneous determination of zeta potential and hydrodynamic sizes. Charging curves obtained in the pH range of 3 to 10 by cyclic titrations reveal the presence of a small hysteresis, proving the chemical stability of SLGO and graphite oxides in weakly acidic and alkaline solutions. HA and SLGO display a parallel shift of the pH-dependencies of their negative charge densities with increasing ionic strength, demonstrating a unique combination of particle and polyelectrolyte-like behaviour, which is absent for multi-layered graphite oxide exhibiting charging curves that resemble to “classical” colloidal particles. An accurate purification of SLGO results in inherent change in its surface properties; however, the salt tolerance of aqueous HA solutions is still superior to that of SLGO dispersions. |
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| Physical Description: | Terjedelem:11-Azonosító:112948 |
| ISSN: | 0167-7322 |