Modified Chitosan Nanofiber Membrane Fabrication for Removal of Pb²⁺ from <i>Coptidis rhizoma</i> Decoction

Heavy metals in medicine are easily introduced during production and processing, and heavy metals pose a risk to human health. To realize the separation of heavy metals from medicine and provide a new method for removing heavy metals, in this study, ethylenediaminetetraacetic acid (EDTA) was used to modify chitosan, and the ethylenediaminetetraacetic acid-modified chitosan (CS-EDTA) fiber membrane was prepared through electrospinning to remove lead ions from Coptidis rhizoma decoction. The effects of spinning speed (0.1 mL/h), modification method (2 g Na2EDTA, 0.1 g EDC, 0.2 g NHS), and pH (pH = 5) on the adsorption capacity were studied. The results showed that the adsorption of Pb2+ on the CS-EDTA membrane was pseudo-second-order kinetics model (R2 > 0.999) and the Langmuir model (R2 > 0.978). The kinetic maximum adsorption capacity of the CS-EDTA membrane was 116.2 mg·g–1. The Pb2+ content in C. rhizoma decoction after adsorption meets the limit requirements for heavy metals specified in the traditional Chinese medicine standard (Pb2+ ≤ 5 mg·kg–1). The chemical composition of the decoction of C. rhizoma did not change significantly after the removal of Pb2+. The membrane has antibacterial properties against Gram-negative bacteria.