Adsorption and Desorption Behavior of Salicylic Acid with Anion Exchange Resin

Adsorption and desorption of aqueous salicylic acid solution,as well as adsorption kinetics and thermodynamics with 717 anion exchange resin were investigated.Results showed that the maximum adsorption ability of resin occurred at pH 4~12.Adsorption of salicylic acid onto resin obeyed Freundlich and Langmuir isotherm,which was a favorable adsorption.At temperature of 298~318 K and adsorption of salicylic acid of 100~120 mg/g,changes of adsorption enthalpy was measures as-23.4~-21.6 kJ/mol,free energy-7.79~-8.01 kJ/mol and entropy of adsorption-52.5~-42.7 J/(K·mol).The adsorption kinetic data of salicylic acid onto resin fitted to Lagergren pseudo-first order rate equation,with the adsorption rate constant of 0.0395~0.056 min-1 and the adsorption activity energy of 13.9 kJ/mol.Besides the intra-particle diffusion,other process such as film diffusion also simultaneously affected the rate of adsorption.Up to 99% of salicylic acid adsorbed in the resin can be easily and quickly eluted with a 5% NaCl and 2% NaOH solution.