Adsorption of levulinic acid from aqueous solution by Amberlite XAD-4

Levulinic acid (LA) from aqueous solutions was removed by using commercial adsorbent Amberlite XAD-4 (XAD-4). The equilibrium and kinetic studies were performed to investigate the effect of adsorbent amount (1 g to 3.5 g at 298 K, 308 K and 318 K), initial acid concentration (2 g·L− 1 to 4 g·L− 1 at 298 K, 308 K and 318 K), and contact time (t, 10 min to 90 min at 298 K) on the capability of XAD-4. The uptake capability and removal efficiency of XAD-4 for the adsorption of LA was observed to increase by increasing amount of adsorbent. In the equilibrium experiments of LA adsorption, adsorption capacity value was increased to 26.85 mg·g− 1 from 10 mg·g− 1 at 298 K with an increase in the amount of XAD-4. In the kinetic studies, the equilibrium time of 70 min was obtained. Also equilibrium study was performed at three different temperatures, 298, 308 and 318 K. The maximum removal was obtained at 298 K. Thermodynamic model parameters such as ∆ G°, ∆ H° and ∆ S° are estimated at three different LA concentration (2 g·L− 1, 3 g·L− 1 and 4 g·L− 1). Different isotherm and kinetic models were applied to estimate the equilibrium and kinetic parameters.