Adsorption differences and mechanism of chitooligosaccharides with specific degree of polymerization on macroporous resins with different functional groups

• Adsorption behaviors of COS 2–5 on different functional groups resins were studied. • Adsorption of COSs on DX-10 resin was an entropy-driven reaction. • Adsorption of COSs on DC-10 resin was an enthalpy-driven reaction. • Particle radius effect kinetic and rate-limiting step is intra-practical diffusion. • Diffusion coefficients of COSs on DX-10 resin are greater than that of DC-10. Ion exchange resins are promising materials for separating chitooligosaccharides (COSs) with different degrees of polymerization (DP). The adsorbent functional groups significantly determine the interactions with COSs and affect their adsorption and separation efficiency. This study investigated the adsorption behaviors of COSs on macroporous cation exchange resins with different functional groups to clarify the functional group effect on the adsorption of COSs with different DP, which can also help to provide a theoretical basis for the selection of separation medium and optimization of the separation technics of COSs. The results showed that the adsorption of COSs on sulfonic-acid type resin DX-10 and carboxylic-acid type resin DC-10 were favorable, and the adsorption isotherms were in accord with the Sips model. Adsorption thermodynamics showed that temperature had opposite effects on the two resins' equilibrium adsorption capacity of COSs. The diffusion coefficient of COSs on DX-10 resin was greater, and the affinity gap between COSs on DX-10 resin was larger than that of DC-10 resin, which is beneficial for improving the separation resolution of COSs. In contrast, the interaction energy between COSs with high DP and DC-10 resin was weaker compared with DX-10, which made the elution of COSs with high DP easier.