Amido-functionalized carboxymethyl chitosan/montmorillonite composite for highly efficient and cost-effective mercury removal from aqueous solution

The efficient and cost-effective removal of mercury (Hg) from water is highly desired. A biopolymer/clay composite adsorbent was developed by introducing montmorillonite modified with sulfhydryl into a hyperbranched polyethylenimine functionalized carboxymethyl chitosan matrix (HPFC/MT-S), which proves to be a superior alternative for the removal of Hg(II) ions from aqueous solutions. The developed adsorbent exhibits excellent adsorption capacity of 1875 mg/g, representing the highest value among the reported polymer/clay composite adsorbents so far, and the concentration of Hg(II) ions was found to decrease from 1000 mg/L to 0.031 mg/L after adsorption by HPFC/28%MT-S, satisfying China’s industrial wastewater emission standards. In addition, the selectivity of the composite for Hg(II) was further improved by the introduction of MT-S, yielding a high distribution coefficient value (Kd = 1.0 × 107). The adsorption capacity of HPFC/MT-S for Hg(II) is not equal to the simple sum of each component in the composite system but higher than that. The improved adsorption performance is mainly contributed to the increased porosities and chelation sites of the adsorbent. The present work suggests the great potential of polymer/clay composite materials in environmental remediation.