Adsorption behavior of levulinic acid onto microporous hyper-cross-linked polymers in aqueous solution: Equilibrium, thermodynamic, kinetic simulation and fixed-bed column studies

The recovery of levulinic acid (LA) from aqueous solution and actual biomass hydrolysate by a micro porous hyper-cross-linked polymer, SY-Ol, was investigated for the first time under batch and fixed-bed column conditions. The results showed that the optimum pH should be in the acidic range (pH<3.0) without adjusting the pH. In the single-component system equilibrium study, the Langmuir isotherm model fits the LA adsorption onto SY-01 resin better than the Freundlich isotherm model, indicating that LA adsorption onto SY-01 resin under the concentration range studied is a monolayer homogeneous adsorption process. The maximum adsorption capacity of LA onto SY-01 resin decreased with increasing temperature, ranging from 103.74 to 95.70 mg/g. The obtained thermodynamic parameters suggested that the adsorption of LA on SY-Ol was spontaneous (Delta G(0) <-3.788 kJ/mol), and exothermic (Delta H-0 = -11.764 kJ/mol). For kinetic study, the adsorption of LA onto SY-Ol resin at various operating conditions follows the pore diffusion model and the intraparticle diffusion is the rate-limiting step for the adsorption of LA onto SY-01 resin. The effective pore diffusivity was dependent upon temperature, but independent of initial LA concentration, and were 3.306x10(-10), 5.274x10(-10) and 7.707x10(-10) m(2)/ s at 298, 318 and 338 K, respectively. In desorption process, the recovery efficiency of LA from SY-Ol resin was 99.39%, and LA concentration in the eluent was raised 2.97-fold. In conclusion, our results show that the SY-01 resin has potential application in product recovery of LA from biomass hydrolysate. (C) 2016 Elsevier Ltd. All rights reserved.