Dissolution-aggregation behavior of water-soluble nanographites and their adsorptive characteristics for 2-naphthol in aqueous solutions.
Carbon black was severely oxidized by concentrated nitric acid at 373 K, and the oxidation product was fractionated by ultrafiltration into five groups of a few nanometer-sized water-soluble aromatic compounds, which we called water-soluble nanographites (WSNG1-5). Most WSNGs dissolve in neutral and alkaline 0.1 moldm(-3) NaCl solutions, but precipitate in acidic solutions. The pH values at which the WSNGs begin to precipitate decreased as the molecular size of the WSNGs was lowered. WSNG3, which possesses a moderate molecular size among the WSNGs, adsorbed more 2-naphthol from acidic solutions than from neutral solutions. The maximum uptake of 2-naphthol on WSNG3 at the saturated concentration was, however, independent of the pH, both resulting in 1.28 mmolg(-1). This quantity indicates that each WSNG3 molecule adsorbs one and one-half 2-naphthol molecules. The maximum uptake was much greater than that of the graphitized carbon black (BET surface area, 77 m(2)g(-1)) and was equal to that of Amberlite XAD-2 (334 m(2)g(-1)). An increase in the molecular size of the WSNGs enhanced the adsorbate-adsorbent interaction, but decreased the maximum uptake of 2-naphthol at the saturated concentration.
Kamegawa
Katsumi
K
National Institute of Advanced Industrial Science and Technology (AIST) Kyushu, 807-1, Shuku, Tosu, Saga, 841-0052, Japan. k.kamegawa@aist.go.jp
Nishikubo
Keiko
K
Kodama
Masaya
M
Adachi
Yoshio
Y
Yoshida
Hisayoshi
H