Recovery of vanillin from aqueous solutions using macroporous adsorption resins

A simple method for recovery of dissolved vanillin from aqueous solutions by the adsorption–regeneration technique has been developed. Three macroporous adsorption resins with crosslinked-polystyrene framework were NKA-2, S-8 and H103, respectively. Static equilibrium adsorption studies were used for comparing the adsorption capacities of the three resins. The results showed that H103 resin had the best adsorption capacity because of its large and nonpolar surface areas. The effects of pH, temperature and salt concentration on the adsorption capacity of H103 were investigated. The results revealed that the resin had a maximum adsorption capacity, 416 mg/g (vanillin/resin) in acidic condition when the molecule of vanillin is neutral. Furthermore, its adsorption capacity increased with the increase of temperature and salt concentration. The mass transfer zone motion model was used for analyzing the fixed bed adsorption. H103 resin had a shorter mass transfer zone of 24.7 cm and both NKA-2 and S-8 were higher than 30 cm in the experiment conditions. More than 95.6% of adsorbed vanillin can be recovered by use of 3–5 bed volumes of absolute ethanol. The resin can be used repeatedly by simple regeneration and its adsorption capacity was almost unchangeable.