Kinetics and equilibrium study for the adsorption of lysine on activated carbon derived from coconut shell

Abstract

ABSTRACT Activated carbon was prepared from coconut shell by a chemical activation method with potassium hydroxide at different temperatures and characterized for pore structure. The adsorption of lysine from aqueous solution by the prepared coconut shell activated carbon was carried out using batch adsorption experiments. The effect of shaking speed, adsorbent dosage, pH, initial lysine concentration and temperature were investigated. The results indicate that coconut shell activated carbon is an effective adsorbent which has a high surface area (1118.2 m 2 /g) and pore volume (0.4992 cm 3 /g). The effect of external diffusion is negligible at 170 rpm, the percent removal of lysine increases with the increment of the adsorbent dosage, the optimum pH is 6. The adsorption equilibrium data obtained at 20, 30 and 40°C agree better with the Langmuir model than with Freundlich model, and the thermodynamics parameters, ΔH = 2.71 kJ/mol, ΔS = 107.2 J/mol·K and ΔG < 0, display that the adsorption process is spontaneous and endothermic. The adsorption kinetics is well described by the pseudo second-order equation. The activated carbon was successfully regenerated by using ammonia as eluent. The results exhibit that coconut shell activated carbon is an efficient and low-cost adsorbent for the removal of lysine from aqueous solutions.