Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was experimentally and theoretically studied. Undissociated salicylic acid was found to be the favorable form for salicylic acid adsorption on the resin. A pH-dependent adsorption isotherm model established in this paper could well fit the adsorption isotherm data at different pH values. Surface diffusion is the main mass-transfer mode for salicylic acid in resin particles. The salicylate anions and Na+ coadsorbed on the resin. The modified surface diffusion model considering the coadsorption was proposed. The model could satisfactorily fit the concentration decay curves of salicylic acid at different pH values and feed concentrations. NaOH aqueous solution at pH 12 could elute salicylic acid in the fixed bed efficiently. A pH-dependent dynamic adsorption and elution process model considering axial diffusion, external mass transfer, surface diffusion, pH-dependent adsorption equilibrium, as well as coadsorption of salicylate anions and Na+ was established. The model could well predict the breakthrough and elution curves at different feed concentrations. The research carried out in this paper has reference significance for optimizing the separation process of salicylic acid and its analogues.

Automated summary

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was studied experimentally and theoretically. The adsorption of undissociated salicylic acid on the resin was found to be favorable, and a pH-dependent adsorption isotherm model was established to fit the experimental data. Surface diffusion was identified as the main mass-transfer mode for salicylic acid in resin particles, with coadsorption of salicylate anions and Na+. A modified surface diffusion model considering coadsorption was proposed and validated with concentration decay curves at different pH values and feed concentrations. Furthermore, a pH-dependent dynamic adsorption and elution process model considering multiple factors was established and successfully predicted the breakthrough and elution curves. This research has reference significance for optimizing the separation process of salicylic acid and its analogues.