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Self Assembled Monolayers on Mesoporous Supports (SAMMS): Surface Functionalized Mesoporous Materials

Awards Won:
FLC Award - 2006
R&D 100 Award - 1998

Battelle Number(s): 11429
Patent(s) Issued
Available for licensing in all fields
  • Shown is a representation of a mercaptopropylsiloxy monolayer covering the pore surfaces, with an enlarged view of a monolayer-coated pore in the background. Red spheres = oxygen, orange = silicon, magenta = carbon, white = hydrogen, yellow = sulfur, and blue = mercury (shown bound to the sulfur).

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Summary

Nano-engineered sorbents, partly organic and partly inorganic, developed at Pacific Northwest National Laboratory, have proven to be exceptionally selective and efficient in removing heavy metals and other contaminants from waste streams. These sorbents are self-assembled monolayers on mesoporous supports-SAMMS-and form effective sorbents for a wide variety of species including mercury, heavy metals, radionuclides and anions. Silica ceramics containing ordered arrays of cylindrical pores are first prepared. The pore diameter can be adjusted from 2 to 20 nm, with 5 to 6 nm being the typical diameter used in the sorbents. The inside surfaces of the channel-like pores are then coated with an organic monolayer whose molecules are covalently bonded to the silica. The free ends of the tethered molecules can be chemically tailored to sequester particular species from solution. The exceptionally high surface area of the mesoporous silica support-typically between 900 and 1,000 square meters per gram-gives the SAMMS a very high binding capacity, with the open-pore structure allowing solution species easy access to the pore surfaces, leading to their rapid sorption. The SAMMS material is readily tailored to absorb the species of interest.

SAMMS is an incredibly versatile material. Uses include waste remediation and stabilization, water treatment, metal finishing, metal processing, ore beneficiation, and catalysis. In addition, work continues on extending SAMMS performance in the following areas: new chelate-SAMMS for transition metals in aqueous systems; stability under extended process conditions and as a final waste form; regeneration methods and the regeneration effectiveness; precious metal recovery; actinide removal from a range of radioactive environments; fundamental science issues related to the synthesis and application of SAMMS.

Possible Applications

  • Remediation: mercury contaminated solutions have been reduced below the toxic threshold discharge limit with SAMMS. The mercury containing SAMMS material is environmentally stable and may land filled.
  • Water treatment: SAMMS has been demonstrated to reduce arsenic (As+3 and As+5) in drinking water to below the 10ppb limit. The arsenic-containing SAMMS material has been shown to be fully regenerable for use.
  • Sensors: SAMMS is readily amenable to being used as an absorbent or concentrator for sensors.
  • Waste stabilization.

Details have been published

  • "Silica Sorbents with a Taste for Metals," Chemical and Engineering News, 15 October 2001, page 31.
  • "Deposition of Self-Assembled Monolayers in Mesoporous Silica from Supercritical Fluids," T.S. Zemanian, et al., Langmuir, 2001, 17, 8172-8177.
  • "Design and Synthesis of Selective Mesoporous Anion Traps," G. E. Fryxell, et al.; Chemistry of Materials, 1999, 11, 2148-2154.
  • "Hybrid Mesoporous Materials with Functionalized Monolayers," Jun Liu, et al., 1998, 10, 161-165.
  • "Functionalized Monolayers on Ordered Mesoporous Supports," Feng, X.; et al., Science, 1997, 276, 923-926.

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