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Metal ion remediation by polyamidoamine dendrimers: a comparison of metal ion, oxidation state, and titania immobilization Castillo, V.A.; Barakat, M.A.; Ramadan, M.H.; Woodcock, H.I. & Kuhn, J.N. Abstract The exceptional ability of dendrimers to coordinate metal ions yields the potential for many applications including wastewater remediation, which is the focus of this study. Here, the comparison of metal ion removal rate from simulated wastewater by generation 4 dendrimers with external hydroxyl functional groups (G4-OH) is evaluated for Ni2+, Fe2+, and Fe3+ ions. Ni2+ to amine complexation occurred more rapidly than Fe3+, which was more rapid than Fe2+ complexation. These results indicate that both charge density and d-electron configuration are important toward the chelation rate. The impact of both factors is discussed in light of existing models in which precursor aquation rates have been proposed as a key intermediate step. Additionally, the application of the dendrimers as chelation agents is further advanced by immobilizing the dendrimer to titania and re-evaluating its chelation ability for Ni2+ removal. The dendrimer immobilization decreased the pseudo-first-order rate coefficient for Ni2+—amine complexation at a pH of 7 by a factor of 7.5. This result is significant as it suggests that mass transfer becomes important following immobilization of the dendrimer to titania. Keywords Wastewater remediation; Polyamidoamine dendrimer; Iron; Nickel; Chelation

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