Aminopoly(carboxylic acid)-Functionalized PolyHIPE Beads toward Eliminating Trace Heavy Metal Ions from Water

Many advanced materials are designed for the removal of heavy metal ions from water. However, materials for eliminating trace heavy metal ions from wastewater to meet drinking water standards remain a major challenge. Herein, epoxy group-functionalized open-cellular beads are synthesized by UV polymerization of a water-in-oil-in-water system. The epoxy groups are further transformed into diethylenetriaminepentaacetic acid (DTPA) with hexamethylene diamine as a bridging agent. The resulting material (DTPA@polyHIPE beads) can eliminate trace Cu(II), Cr(III), Pb(II), Fe(III), or Cd(II) from water. When 0.15 g of DTPA@polyHIPE beads are used to adsorb metal ions of 20 mg in 100 mL of water, the residue concentrations of Cu(II), Cr(III), Pb(II), Fe(III), and Cd(II) are reduced to 0.08, 0.06, 0.02, 0.09, and 0.07 mg/L, respectively. The adsorption efficiencies of the beads for these ions are all higher than 99.55%. The adsorbent is durable and exhibits good recyclability by retaining an adsorption capacity of ≥91% after 5 cycles. The negative values of ΔG in the adsorption process indicate that the adsorption is feasible and spontaneous. The chemical adsorption follows the Freundlich adsorption model, indicating a multilayer heterogeneous adsorption. The DTPA@polyHIPE beads have a great potential application in dealing with trace heavy metal ion polluted water.