Article pubs.acs.org/est
Collection of Lanthanides and Actinides from Natural Waters with Conventional and Nanoporous Sorbents Bryce E. Johnson, Peter H. Santschi,* Chia-Ying Chuang, and Shigeyoshi Otosaka Department of Marine Science, Texas A&M University, Galveston, Texas 77553, United States
Raymond Shane Addleman,* Matt Douglas, Ryan D. Rutledge, Wilaiwan Chouyyok, Joseph D. Davidson, Glen E. Fryxell, and Jon M. Schwantes Pacific Northwest National Laboratory, Richland, Washington 99352, United States S Supporting Information *
ABSTRACT: 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 MnO2 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.
■
migration through the environment and bioavailability.9,11 Lanthanide elements (plus yttrium) account for approximately 40% by mass of the atoms resulting from fission of uranium and plutonium and are thus present in significant quantities in nuclear fallout and waste streams.12,13 Herein, we explored and evaluated the collection of lanthanides and actinide isotopes from natural waters with conventional and nanoporous sorbents. High affinity sorbents can enable the collection of trace and ultratrace levels of lanthanide and actinides from aqueous
INTRODUCTION The world is looking to augment its energy needs with the development of nuclear technology. However, as accidents in Chernobyl Ukraine and Fukushima Japan show, environmental contamination of potentially toxic radioactive species can be a real and significant hazard.1−3 Additionally, over 70 years of nuclear operations have led to a legacy of nuclear waste and a range of storage and disposal issues.4−6 Unfortunately, many of the highly radioactive species associated with the processing of nuclear fuels and disposal of nuclear wastes are known to possess long half-lives and high levels of mobility in the environment.6−10 For example, many lanthanides and actinides are known to not only possess highly adsorptive properties, causing them to bind not only to mineral particles, but also to colloids and natural organic matter thus facilitating their © 2012 American Chemical Society
Received: Revised: Accepted: Published: 11251
November 22, 2011 August 20, 2012 September 17, 2012 October 3, 2012 dx.doi.org/10.1021/es204192r | Environ. Sci. Technol. 2012, 46, 11251−11258
Environmental Science & Technology
■
Article
MATERIALS AND EXPERIMENTAL METHODS General Considerations and Characterization. Polymeric ion exchange resins were purchased from Biorad Laboratories (Hercules, CA, U.S.A). MnO2 powders and all remaining chemicals were obtained from Sigma Aldrich (St. Louis, MO, U.S.A) and used as received. Brunauer−Emmett− Teller (BET) surface area measurements were determined by nitrogen adsorption at 77 K on a Quantachrome Autosorb 6. Organic content and ligand densities were of sorbent materials determined on a NETZCHE Thermogravimetric Analyzer (TGA) under a flow of ambient air. Total organic carbon (TOC) was determined using a Shimadzu TOC-5000 for each of the tested waters. Sorbent Materials. Basic physical sorbent characteristics are provided in Table SI-2 of the Supporting Information. The conventional materials consisted of both a strong anion exchange (SAX) polymeric resin (AG MP1) based upon quaternary ammonium salt chemistry, a strong cation exchanger (SCX) based upon sulfonic acid chemistry, and the EDTAbased polymeric resin (Chelex 100). In addition, three different forms of MnO2 material were studied, including two different sizes (
