An electroactive montmorillonite/polypyrrole ion exchange film: Ultrahigh uptake capacity and ion selectivity for rapid removal of lead ions.

Contact with trace heavy metal contaminants will also lead to extremely bad health influence on human body and aquatic life. Although various adsorbents have been synthesized for the recovery of heavy metal ions, most of them shows deficient adsorption capacity, sluggish uptake rate and low selectivity. In this study, a montmorillonite/polypyrrole (MMT/PPy) film was successfully synthesized by intercalating polymers PPy into the interlayer of MMT nanosheets for selective and rapid capture of Pb. The electroactive film has ultrahigh uptake capacity (1373.29 mg⋅g), which is much higher than most conventional Pb adsorbents. Meanwhile, it had an extreme selectivity towards Pb due to the MMT/PPy film can accurately identified Pb. Through characterization testing and data analysis, the selective and rapid uptake/release of Pb should be realized through three ways: (1) negatively-charged laminates of MMT can generate electrostatic attraction to Pb; (2) -OH on the surface of MMT laminates can accurately identified and bonded with Pb (M-O-H↔ M-O-Pb); (3) PPy doped by PSS and protic acid can rapidly catch Pb (PPy·PSS+Pb+e→ PPy·PSS·Pb). Therefore, such a novel MMT/PPy nanocomposite film could has evident application prospect to remove Pb from various water bodies.