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

Abstract Activated carbons were synthesized by FeCl 3 -activation of Tara gum at different temperatures (400–1000 °C). The activating agent and the precursor were physically mixed at different ratios (r = FeCl 3 :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 m 2 ·g −1 and a pore volume near 1 cm 3 ·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.