Effective collection of trace-level lanthanides and actinides is advantageous for recovery and recycling of valuable resources, environmental remediation, chemical separations, and in situ monitoring. Using isotopic tracers, we have evaluated a number of conventional and nanoporous sorbent materials for their ability to capture and remove selected lanthanides (Ce and Eu) and actinides (Th, Pa, U, and Np) from fresh and salt water systems. In general, the nanostructured materials demonstrated a higher level of performance and consistency. Nanoporous silica surface modified with 3,4-hydroxypyridinone provided excellent collection and consistency in both river water and seawater. The MnO(2) materials, in particular the high surface area small particle material, also demonstrated good performance. Other conventional sorbents typically performed at levels below the nanostructured sorbents and demonstrate a larger variability and matrix dependency.

Iminodiacetic acid (IDAA) forms strong complexes with a wide variety of metal ions. Using self-assembled monolayers in mesoporous supports (SAMMS) to present the IDAA ligand potentially allows for multiple metal-ligand interactions to enhance the metal binding affinity relative to that of randomly oriented polymer-based supports. This manuscript describes the synthesis of a novel nanostructured sorbent material built using self-assembly of a IDAA ligand inside a nanoporous silica, and demonstrates its use for capturing transition metal cations, and anionic metal complexes, such as PdCl4−2.

Copper has been identified as a pollutant of concern by the Environmental Protection Agency (EPA) because of its widespread occurrence and toxic impact in the environment. Three nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu2+ adsorption from natural waters -- ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS®), ethylenediamine functionalized activated carbon (AC-CH2-EDA), and 1,10-Phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu2+ sorption, Cu2+ sorption capacities, rates, and selectivity of the sorbents were determined and compared with those of commercial sorbents (Chelex-100 ion exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed excellent Cu2+ removal (~95–99%) from river water and sea water over the pH range of 6.0–8.0. EDA-SAMMS and AC-CH2-EDA demonstrated rapid Cu2+ sorption kinetics (minutes) and good sorption capacities (26 and 17 mg Cu/g sorbent, respectively) in sea water, while Phen-FMC had excellent selectivity for Cu2+ over other metal ions (e.g. Ca2+, Fe2+, Ni2+, and Zn2+) and was able to achieve Cu levels below the EPA standards for river and sea waters.

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