Adsorption of phenol onto chitosan hydrogel scaffold modified with carbon nanotubes

Abstract Chitosan hydrogel scaffold modified with carbon nanotubes (HyCNT) was produced and applied for phenol adsorption. Adsorbent was characterized from scanning electron microscopy (SEM), infrared spectrum (FT-IR), atomic force microscopy (AFM), crosslinking degree (CD), gel strength (GS) and Bennett, Emmet and Teller (BET) method. Isotherms were performed in different temperatures. The experimental data were adjusted to the Freundlich, Dunibin-Radushkevich and Temkin isotherm models and thermodynamics parameters were estimated. The kinetics behavior were evaluated using different stirring rate (50, 100 and 150 rpm). The results show the adsorbent presented a porous surface and heterogeneous structure and was possible proved the modification of hydrogel in relation to the crosslinking agent and the insertion of the carbon nanotubes. The HyCNT presented specific surface area of 1130 m2 g-1 and pore sizes from 40 to 150 µm. AFM images show the formation of carbon nanotubes clusters in the chitosan matrix. The Dubinin-Radushkevic model was the most appropriated to represent the equilibrium data and the maximum adsorption capacity was 404.2 ± 2.10 mg g-1, at 30 °C. Thermodynamics parameters indicated that the adsorption was favorable and exothermic with an enthalpy change of -50.01 ± 0.20 kJ mol-1. The pseudo-second-order model kinetic was the most adequate to represent the phenomenon of adsorption at all rotations.