Adsorption Kinetics and Thermodynamics of Auramine-O on Sugarcane Leaf-Based Activated Carbon

The removal efficiency, adsorption kinetics, and thermodynamics of Auramine-O (AO) onto sugarcane leaf-based activated carbon prepared by ammonium dihydrogen phosphate were investigated systematically. The optimal AO removal conditions were found to infuse 1.2 g/L sugarcane leaf-based activated carbon in 200 mg/L AO solution which the initial pH (pH0) was 9.0 for 180 minutes. The adsorption kinetics of AO was described well by the pseudo-second-order and intra-particle diffusion model. The intra-particle diffusion was not the exclusive rate controlling step in the adsorption process. The isotherm obeyed the Langmuir isotherm with a high correlation coefficient (R2 > 0.99), and the thermodynamic analysis suggested that ΔG < 0, ΔH > 0, and ΔS > 0, which indicated that the adsorption of AO onto sugarcane leaf-based activated carbon was a spontaneous chemical and endothermic adsorption process.