Construction of Active Sites in Porous Organic Polymers for Various Heavy Metal Ions Capture

Heavy metal pollution is directly related to human health and life safety, and the development of broad-spectrum and high-efficiency heavy metal adsorbents is expected to solve the problem of coexistence of multiple heavy metal pollutants in industrial wastewater. A triptycene-based porous organic polymer (TPOP) with high specific surface area was produced by crosslinking three-dimensional rigid triptycene monomer through the simple Friedel-Crafts alkylation reaction. Then, a broad-spectrum heavy metal ions adsorption active site (TPOP-CH(2)EDTA) was constructed in TPOP by grafting of ethylenediamine and sodium chloroacetate. The obtained TPOP-CH(2)EDTA showed a micro/mesoporous structure, with the main micropore size of 1.6 nm and the BET surface area of 634 m(2)/g, which facilitates the transfer and coordination of heavy metal ions. TPOP-CH(2)EDTA has a broad-spectrum adsorption for heavy metal ions, like Ag(I), Cu(II), Ni(II), Zn(II), Co(II), Sn(IV), Pb(II), Cd(II), Fe(III), Cr(III) are investigated, respectively, and the removal efficiency are all higher than 98%. Taking Pb(II) as a typical heavy metal pollutant, the maximum adsorption capacity of Pb(II) is calculated up to 184.5 mg/g by the Langmuir model. The kinetic study shows that it is a Pseudosecond-order adsorption, fast adsorption rate, and the kinetic constant k(2) of 0.0173 g.mg(-1).min(-1). After 5 recycling use, the removal efficiency of Pb(II) is still as high as 95.8%. More significantly, the removal efficiency of Pb(II) and Cu(II) in their mixture solution is either higher than 99%. For the complex real water containing large amounts of inorganic salts, like Ca(II), Mg(II), K(I), Na(I) ions, and organic compounds, the removal efficiency of Pb(II) and Cu(II) still maintains higher than 90%. Therefore, a broad-spectrum heavy metal ion adsorption active site is constructed by controlling the microstructure of porous organic polymers (such as specific surface area, pore size and adsorption site density), which provides a scheme for the coordinated removal of mixed heavy metal ions in complex water systems.