Adsorption of vanillic and syringic acids onto a macroporous polymeric resin and recovery with ethanol:water (90:10 %V/V) solution

In this work the adsorption of vanillic (VA) and syringic (SA) acids onto the nonpolar resin SP700 was investigated aiming to collect data to evaluate their separation from a lignin oxidation mixture containing other phenolic compounds. The respective adsorption equilibrium isotherms in aqueous solutions were assessed at three different temperatures 288, 298 and 333 K and experimental results were fitted with Bi-Langmuir isotherm model. Maximum adsorption capacities of 0.486 g g−1dry resin and 0.407 g g−1dry resin were obtained for VA and SA, respectively. Dynamic studies at different temperatures and feed concentrations were performed and a mathematical model comprising the Bi-Langmuir equilibrium isotherm, axial dispersed plug flow, intraparticle mass transfer resistance expressed with linear driving force approximation with no temperature gradients and constant porosity along the bed successfully described the adsorption concentration histories at the outlet of the fixed bed. More than 83% of each phenolic acid was readily eluted within 5 min elution with ethanol:water (90:10 %V/V) solution allowing obtaining a final concentrated solution with 5.8–11.7 g L−1.