skip to main content

Search for: All records

Creators/Authors contains: "Forbes, Tori Z."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available October 1, 2023
  2. Through a combination of many analytical approaches, we show that a metal organic nanotube (UMON) displays selectivity for H 2 O over all types of heavy water (D 2 O, HDO, HTO). Water adsorption experiments combined with vibrational and radiochemical analyses reveal significant differences in uptake and suggest that surface adsorption processes may be a key driver in water uptake for this material.
  3. Uranium (U) contamination of drinking water often affects communities with limited resources, presenting unique technology challenges for U 6+ treatment. Here, we develop a suite of chemically functionalized polymer (polyacrylonitrile; PAN) nanofibers for low pressure reactive filtration applications for U 6+ removal. Binding agents with either nitrogen-containing or phosphorous-based ( e.g. , phosphonic acid) functionalities were blended (at 1–3 wt%) into PAN sol gels used for electrospinning, yielding functionalized nanofiber mats. For comparison, we also functionalized PAN nanofibers with amidoxime (AO) moieties, a group well-recognized for its specificity in U 6+ uptake. For optimal N-based (Aliquat® 336 or Aq) and P-containing [hexadecylphosphonic acid (HPDA) and bis(2-ethylhexyl)phosphate (HDEHP)] binding agents, we then explored their use for U 6+ removal across a range of pH values (pH 2–7), U 6+ concentrations (up to 10 μM), and in flow through systems simulating point of use (POU) water treatment. As expected from the use of quaternary ammonium groups in ion exchange, Aq-containing materials appear to sequester U 6+ by electrostatic interactions; while uptake by these materials is limited, it is greatest at circumneutral pH where positively charged N groups bind negatively charged U 6+ complexes. In contrast, HDPA and HDEHP perform best at acidicmore »pH representative of mine drainage, where surface complexation of the uranyl cation likely drives uptake. Complexation by AO exhibited the best performance across all pH values, although U 6+ uptake via surface precipitation may also occur near circumneutral pH values and at high (10 μM) dissolved U 6+ concentrations. In simulated POU treatment studies using a dead-end filtration system, we observed U removal in AO-PAN systems that is insensitive to common co-solutes in groundwater ( e.g. , hardness and alkalinity). While more research is needed, our results suggest that only 80 g (about 0.2 lbs.) of AO-PAN filter material would be needed to treat an individual's water supply (contaminated at ten-times the U.S. EPA maximum contaminant level for U) for one year.« less
  4. Behavior of nanoconfined water in porous materials has important implications for the development of advanced water purification and storage. In the current study, the kinetics of water sorption from the vapor phase into a metal organic nanotube ((C 4 N 2 H 6 )[(UO 2 )(C 4 O 4 NH 5 )(C 4 O 4 NH 6 )]·2H 2 O (UMON)) are investigated with varying relative humidity. The UMON compound contains nanoconfined water molecules arranged in an ice-like array along the length of its one-dimensional pore and exhibits complete specificity to liquid water. Total hydration of the material is observed upon exposure to relative humidity of 60% or higher. Water uptake curves are modeled as diffusion and irreversible condensation in the pore, which leads to a modeled diffusion coefficient of (1.2 ± 0.6) × 10 −12 cm 2 s −1 for water in UMON nanochannels. This value is much lower than observed for other porous material and is most similar to water diffusivity in low-density amorphous ice. In addition, on exposure to various solvent vapors, the UMON material maintained specificity for water in the gas phase.