Purification of Panax notoginseng Saponins by Rosin-based Adsorption Resin and the Associated Adsorption Mechanism
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Abstract:
A new type of rosin-based adsorption resin (RBAR) was synthesized using divinylbenzene as a cross-linker and hydrogenated rosin (β-acryloxylethyl) ester and methacrylic acid as functional monomers. The RBAR was characterized by FT-IR, TGA, particle size analysis, SEM, and N2 adsorption–desorption isotherm analysis. Moreover, the adsorption of RBAR for Panax notoginseng saponins (PNS) was also examined. The results showed that RBAR had good thermal stability, uniform particle size distribution, a regular spherical shape, a relatively high specific surface area (563.37 m2/g), and a highly micro/mesoporous structure. Moreover, RBAR exhibited a high adsorption capacity (127.97 mg/g) for PNS under the following conditions: initial concentration of 6 mg/mL, temperature of 328 K, a solid-liquid ratio of 0.046 g/mL, and adsorption time of 180 min. The resin can be regenerated with 70% ethanol; after being reused ten times, the adsorption rate remained >97%. Under optimal conditions, the PNS mass fraction increased from 46% to 80% following purification by RBAR. Additionally, RBAR exhibited better desorption and purification than commercial resin D101. Through adsorption kinetics, isotherm evaluation, thermodynamic model fitting, and pore structure characterization, the adsorption mechanism of RBAR for PNS was explored. The mass transfer process was primarily controlled via liquid film diffusion, conforming to the pseudo-first-order kinetics. Furthermore, the adsorption isotherms conformed to the Freundlich isotherm model, and the adsorption mechanism comprised heterogeneous multilayer physical adsorption. More specifically, hydrophobic interactions, hydrogen bonding, and pore filling collectively contribute to the driving force behind the adsorption of PNS. These findings offer a theoretical foundation for developing new PNS purification technologies.
