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Evidence is presented here that water contaminated with toxic metal ions can be cleaned with PAMAM dendrimers. This new class of highly branched polymers can bind up 153 plus or minus 20 Cu(II) ions per molecule. These numbers are substantially higher than traditional chelating agents, such as trithylene tetramine and macrocyles. The metal-laden dendrimers can then be separated from solution via ultrafiltration. Once used, the dendrimers can be regenerated by protonation of the ligands. Such recycling of the dendrimers will help keep down processing costs.

Many new water treatment systems operate by enhancing the solubility of organic pollutants that are hydrophobic. Such water treatment procedures allow contaminated water to be detoxified with the use of solutions of surfactants that are ethoxylated and nonionic. An investigation into the enhancement of hydrocarbon solubilization is presented to illustrate how the use of micellar solutions of dodecyl alcohol ethoxylates can be applied in water treatment systems.

Dendritic nanomaterials are emerging as key building blocks for a variety of nanoscale materials and technologies. Poly(amidoamine) (PAMAM) dendrimers were the first class of dendritic nanomaterials to be commercialized. Despite numerous investigations, the environmental fate, transport, and toxicity of PAMAM dendrimers is still not well understood. As a first step toward the characterization of the environmental behavior of dendrimers in aquatic systems, we measured the octanol-water partition coefficients (log Kow) of a homologous series of PAMAM dendrimers as a function of dendrimer generation (size), terminal group and core chemistry. We find that the logKow of PAMAM dendrimers depend primarily on their size and terminal group chemistry. For G1-65 PAMAM dendrimers with terminal NH2 groups, the negative values of their logKow indicate that they prefer to remain in the water phase. Conversely, the formation of stable emulsions at the octanol-water (O/W) interface in the presence of G6-NH2 and G8-NH2 PAMAM dendrimers suggest they prefer to partition at the O/W interface. In all cases, published studies of the cytotoxicity of Gx-NH2 PAMAM dendrimers show they strongly interact with the lipid bilayers of cells. These results suggest that the log Kow of a PAMAM dendrimer may not he a good predictor of its affinity with natural organic media such as the lipid bilayers of cell membranes. [ABSTRACT FROM AUTHOR]

Perchlorate (ClO4-) has emerged as a major groundwater and surface water contaminant in the United States. Ion exchange (IX) is the most widely used technology for treating water containing lower concentrations of perchlorate (<100 ppb). However, a major drawback of IX is the need for frequent regeneration or disposal of the perchlorate-laden resins. As a first step toward the development of high-capacity, selective and recyclable dendritic ligands for the recovery of perchlorate from aqueous solutions by dendrimer filtration, we tested the hypothesis that dendrimers with hydrophobic cavities and positively charged internal groups should selectively bind ClO4- over more hydrophilic anions such as Cl-, NO3-, SO42-, and HCO3-. We measured the uptake of ClO4- by the fifth generation (G5-NH2) poly(propyleneimine) (PPI) dendrimer with a diaminobutane core and terminal NH2 groups in deonized water and model electrolyte solutions as a function of (i) anion-dendrimer loading, (ii) solution pH, (iii) background electrolyte concentration, and (iv) reaction time. The ClO4- binding capacity of this dendrimer is comparable to those of perchlorate-selective IX resins. However, its ClO4- binding kinetics is faster and reaches equilibrium in ~1 h. Note also that only a high pH (~.9.0) aqueous solution is needed to release more than 90% of the bound ClO4- anions by deprotonation of the dendrimer tertiary amine groups. The overall results of this study suggest that dendritic macromolecules such as the G5-PPI NH2 dendrimer provide ideal building blocks for the development of high-capacity, selective and recyclable ligands for the recovery of anions such as perchlorate from aqueous solutions by dendrimer enhanced filtration. [ABSTRACT FROM AUTHOR]

This article discusses the feasibility of using dendrimer enhanced ultrafiltration (DEUF)to recover Cu(ll)from aqueous solutions. Building upon the results of fundamental investigations of Cu(ll) binding to PAMAM dendrimers with ethylenediamine (EDA) core and terminal NH2 groups, we combine (i) dead-end ultrafiltration (UF) experiments with (ii) atomic force microscopy (AFM) characterization of membrane fouling to assess the feasibility of using DEUF to recover Cu(ll) from aqueous solutions. On a mass basis, the Cu(ll) binding capacities of the EDA core PAMAM dendrimers are much larger and more sensitive to solution pH than those of linear polymers with amine groups. The dendrimer-Cu(ll) complexes can be efficiently separated from aqueous solutions by ultrafiltration. The metal ion laden dendrimers can be regenerated by decreasing the solution pH to 4.0; thus enabling the recovery of the bound Cu(ll) ions and recycling of the dendrimers. The UF measurements and AFM characterization studies show that EDA core PAMAM dendrimers with terminal NH2 groups have very low tendency to foul the commercially available regenerated cellulose (RC) membranes evaluated in this study. The overall results of these experiments suggest that DEUF is a promising process for recovering metal ions such as Cu- (II) from aqueous solutions. [ABSTRACT FROM AUTHOR]