Equilibrium and kinetic studies of ferulic acid adsorption by Amberlite XAD-16

Ferulic acid (FA) is a valuable organic antioxidant, which is contained in various grains and fruits. FA is usually found in water streams of food industry. In order to find an alternative method for recovery of FA, this study was focused in adsorption of FA on XAD-16. The pH effect (2–8) and the contact time effect (1–180 min) on adsorption capacity were evaluated. The adsorption capacity was highly dependent on pH and the maximum adsorption capacity was found at pH 3 (133 mg FA/g): the adsorption process was well described by the Freundlich isotherm model. Moreover, the adsorption kinetics were conducted by a rapid initial uptake (0–20 min), followed by a slow approach to equilibrium (20–90 min). The kinetic studies showed that the adsorption rate was well described by the Crank model (deviation < 5%), besides that the controlling adsorption mechanism was intraparticle diffusion (Di = 7.18 × 10−8 cm2/s). Finally, based on these results, Amberlite XAD-16 has a superior or equal FA adsorption capacity and rapid kinetics than other adsorbents reported in literature, hence this could be considered to be used at industrial scale.

► Amberlite XAD-16 removed ferulic acid from aqueous solution.
► Acid conditions enhance the adsorption capacity.
► The rate-limiting step for the adsorption kinetics was the intraparticle diffusion.