EGTA-Modified Cotton Fiber Adsorbents for the Removal of Cd²⁺, Pb²⁺, and Hg²⁺ from Chinese Herb Extracts

The recent discovery of heavy metal pollution in Chinese herbs has raised serious concerns for both human health and the environment. Researchers’ attention has been drawn to the toxicity and bioaccumulation of heavy metal ions. In this paper, a new technical method for preparing ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetra acetic acid (EGTA)-functionalized cotton fiber was innovatively proposed, and on this basis, heavy metal ions were successfully removed. First, the surface of cotton fiber (FC) was modified with amino group by reactive dye dyeing method to obtain FN (amino-modified cotton fiber). Subsequently, EGTA anhydride was grafted onto FN to obtain FNE (EGTA-modified cotton fiber). The interaction between materials and metal ions was systematically studied by isothermal titration calorimetry and other methods. The results showed that the adsorption capacity of FNE for Cd²⁺, Pb²⁺, and Hg²⁺ could reach 18.87, 25.84, and 6.69 mg/g, respectively. More importantly, FNE can be reused at least five times in an acidic environment. Furthermore, it is possible to efficiently eliminate heavy metal ions from Chinese herb extracts without compromising the active ingredients. This research provides a brand-new idea and method for solving the problem of removing heavy metal ions from Chinese herb extracts.