Rosin polymer microspheres doped with diatomite for purification of panax notoginseng saponins: Adsorption performance and mechanism investigation

Our current adsorbents have a limited capacity for adsorbing Panax notoginseng saponins (PNS). To address this issue, we synthesized a novel bioadsorbent called rosin polymer/diatomite microspheres (RPM/DT). This was done by doping diatomite (DT), an inorganic substance, with rosin-based organic compounds. PNS's adsorption capacity on RPM/DT is 427.96 mg·g−1, which is 6.5 times that of current adsorbents. RPM, without DT, displayed only 125.10 mg·g−1. This considerable difference in adsorption capacity can be attributed to the physical incorporation of DT into and onto the surface of RPM/DT. In addition, the incorporation plays a crucial role in creating pores, resulting in a remarkable increase in the specific surface area of RPM/DT (734.55 m2·g−1), surpassing that of RPM (405.17 m2·g−1). Additionally, using RPM/DT resulted in a significant increase in PNS purity, rising from 48.47 % to 86.16 %. We investigated the isotherm, kinetics, and thermodynamic properties of PNS on RPM/DT and found that the adsorption is spontaneous, endothermic, and predominantly chemisorptive. Quantum chemical calculations further revealed the adsorption mechanism of PNS on RPM/DT. The functional monomer molecules RPM/DT interacted with Rb1, involving van der Waals forces, H-bonds, and intermolecular electrostatic interactions. In summary, RPM/DT is an efficient and reusable biosorbent with the potential to be used in the separation and enrichment of PNS from crude solutions.