Adsorption of antipyrine by activated carbons from FeCl3-activation of Tara gum

Abstract

Activated carbons were synthesized by FeCl3-activation of Tara gum at different temperatures (400–1000 °C). The activating agent and the precursor were physically mixed at different ratios (r = FeCl3:precursor, 0.5–3.0 wt). At r = 2 and 800 °C the most developed porosity was achieved, with a BET surface area of 1680 m2·g-1 and a pore volume near 1 cm3·g-1, corresponding mostly to micropores (˜75%). The carbons were fully characterized and tested for the aqueous-phase adsorption of antipyrine, used as model emerging pollutant. The kinetic curves and adsorption isotherms at 20, 40 and 60 °C were obtained, which fitted well to hyperbolic and Langmuir equations, respectively. At 20 °C, the saturation adsorption capacity was around 275 mg·g-1 AC. The free energy of adsorption varied from -40.2 to -35.7 kJ·mol-1, while values close to -3 kJ·mol-1 and 112 J·mol-1·K-1, were obtained for the enthalpy and entropy of adsorption, respectively.