Poly(methacrylate citric acid) with good biosafety as nanoadsorbents of heavy metal ions

Heavy metal ion in aqueous solutions has been a challenge to human health. Discovering efficient adsorbents to remove heavy metal ion from water can help address this problem. In this study, poly(methacrylate citric acid) (PCA) with a well-defined structure based on a hydrophilic citric acid monomer was synthesized and then applied as a nanoadsorbent to remove several heavy metal ion. PCA presented excellent solubility in aqueous solution, and after freeze-drying, a loose porous structure was observed. PCA exhibited higher adsorption capacity for all the heavy metal ions (Cu²⁺, Pb²⁺, and Cd²⁺) than citric acid, and had a selectivity for Pb²⁺ ions with a removal efficiency of >90%. PCA also showed a good selectivity for adsorption of Pb²⁺ in a Chinese medicine decoction, with a removal rate >50%, while the concentration of active ingredient was maintained. Cell cytotoxicity in a cell model and system toxicity in mice indicated good biosafety of PCA. These results suggested that PCA with a good biosafety could be utilized as nanoadsorbent to remove Pb²⁺ ion from aqueous solution and decoction.