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

Activated carbons were synthesized by FeCl3-activation of Tara gum at different temperatures (400-1000 degrees 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 degrees 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 (approximate to 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 degrees C were obtained, which fitted well to hyperbolic and Langmuir equations, respectively. At 20 degrees 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.