Demonstration of Mercury Sorbents to Meet DOE Customer Needs
Many sorbents have been developed for the removal of mercury and heavy metals from water; however, the majority of data published to date do not address the removal of mercury to the target levels represented in this project. The application for which these sorbents were targeted for use was the removal of mercury from microgram-per-liter levels to low nanogram-per-liter levels. Overall, the thiol-based resins had the best performance when removing low concentrations of mercury in water at two U.S. Department of Energy facilities in field experiments. It was difficult to achieve the targeted low nanogram-per-liter levels at both sites; however, a substantial amount of mercury was removed by the resins. This is attributed to the mercury speciation, since filtration tests have shown that a significant portion of the mercury at each test location is particle bound or associated with particulate and colloidal matter. The engineered Self-Assembled Mercaptan on Mesoporous Silica (SAMMS) material proved to be as effective as some of the commercial sorbents in removing mercury at the Nonradiological Wastewater Treatment Plant (NRWTP) at Oak Ridge National Laboratory. The material performed almost as well as some of the best sorbents at the Upper East Fork Poplar Creek site at the Oak Ridge Y-12 Plant. The most effective sorbents were SAMMS; Keyle:X, by SolmeteX, Inc.; and SIR-200, by ResinTech, Inc. It was also found that the Keyle:X performed better at the NRWTP when the water was pretreated with hypochlorite to oxidize some mercury species. Because of the scattering of data, mathematical modeling was limited to predicting the behavior of active mercury. Since the field samples contained a substantial amount of particle-bound mercury, the mathematical models did not represent the field data very well. Nevertheless, it was useful to predict the performance of these sorbents at very low concentrations of mercury. Mathematical modeling was also used to investigate the possible wall effects in the small-scale studies. Based on a theoretical derivation of relationships, supported by the field data, it was concluded that wall effects played a very minor role in the experiments. The most important factor that governed the performance of the sorbents at high flow rates was the diffusion of mercury inside the sorbent. It was found that the values for the effective diffusivities were quite high, possibly due to blockage of macropores by the particulates. Estimation of construction costs for treatment system indicated that the specialized sorbents would have to operate at flow rates 3 to 6 times higher than that of a comparable granular activated carbon (GAC) system in order to have the same construction cost. The sorptive capacity of the specialized sorbents would need to be substantially higher than that of the GAC.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 820818
- Report Number(s):
- ORNL/TM-2000/12; TRN: US200405%%224
- Resource Relation:
- Other Information: PBD: 8 May 2000
- Country of Publication:
- United States
- Language:
- English
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