Physico-Chemical nanomaterials science

Adsorption of Sr2+ and Cu2+ from aqueous solutions by surface aminated nanoporous activated carbon fibers

Diyuk V. E.1., Grishchenko L. M.1, Klymchuk V. Yu.1, Mischanchuk A. V.2, Mariychuk R.3, Boldyrieva O. Yu.1, Lisnyak V. V.1,3
1 Faculty of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Street, 64/13, Kyiv 01601, Ukraine.
E-mail: ob@univ.kiev.ua
2 Chuiko Institute of Surface Chemistry of NAS of Ukraine, General Naumov Street, 17, Kyiv 03164, Ukraine.
3 Prešov Universirty in Prešov, Ul. 17 novembra, 1, Prešov 15 080 01, Slovakia.

Here we report on the chemical, thermal and adsorption properties of surface aminated nanoporous activated carbon fibers (ACFs). The bromination of nanoporous ACFs by using treatment with liquid bromine was followed by amination with selected amine: ethylenediamine, diethylamine, monoethanolamine, or sulfolanylethylenediamine to lead to an efficient two-step synthesis of the surface-aminated nanoporous ACFs. Elemental analysis was indicated a grafting density of about 1.0 mmol of bromine per gram of nanoporous ACFs. Brominated surface has reasonable hydrolytic stability in hot water, at below 100 °C, which is a reason for the substitution of 62–95% of the surface bromine by amino groups. The surface-aminated nanoporous ACFs have moderate heat resistance and thermal stability; thermal decomposition and detachment of amino groups are registered between 170 and 460 °C. Effective adsorption of 80–90% of copper (II) and cadmium (II) metal ions from very dilute water solutions were achieved with the surface-aminated nanoporous ACFs. Experimental adsorption data were analyzed by fitting them to the Langmuir and Dubinin-Radushkevich (DR) isotherms. In this way, we proved sufficient energy homogeneity of the carbon surfaces and suggested adsorption in the nanopores of the carbon sorbents, correspondingly. For the surface-aminated nanoporous ACFs, the constant describing the adsorption/desorption equilibrium for each model have the values by 4 to 6 times higher while the DR adsorption energies have the values only by 1.5 to 3 times higher than those found for unmodified nanoporous ACFs.