Bioinspired Macrocyclic Molecule Supported Two-Dimensional Lamellar Membrane with Robust Interlayer Structure for High-Efficiency Nanofiltration

2D lamellar membranes (2DLMs) are used for efficient desalination and nanofiltration. However, weak interactions between adjacent stacked nanosheets result in susceptibility to swelling that limits practical applicability. Inspired by the super adhesion of multi-point suction cups on octopus tentacles, a 2DLM is constructed from Ti₃ C₂ T_x MXene supported by the macrocyclic "multi-point" molecule cucurbit[5]uril (CB5) and demonstrated for nanofiltration of methyl blue (MB) and enrichment of uranyl carbonate. Experimental results and density functional theory calculations indicate that CB5 rivets to the surface of the nanoflakes through strong stable interactions between its multiple binding sites and surface hydroxyl functional groups on MXene nanosheets. This novel 2DLM exhibits excellent nanofiltration performance (69 L m^-2 h^-1 bar^-1 permeance with 93.6% rejection for MB) and can be recycled at least 30 times without significant degradation. The 2DLM exhibits excellent swelling resistance at high salinity, with a demonstration of selective enrichment of uranyl carbonate from artificial water and natural seawater. The results provide a new strategy for constructing highly stable 2DLMs with interlayer spacing controllable from sub-nano to nanometer scales, for size-selective sieving of molecules and ions, high-efficiency nanofiltration, and other applications.

Dose-response relationships between internally-deposited uranium and select health outcomes in gaseous diffusion plant workers, 1948-2011

OBJECTIVE

To examine dose-response relationships between internal uranium exposures and select outcomes among a cohort of uranium enrichment workers.

METHODS

Cox regression was conducted to examine associations between selected health outcomes and cumulative internal uranium with consideration for external ionizing radiation, work-related medical X-rays and contaminant radionuclides technetium (⁹⁹ Tc) and plutonium (²³⁹ Pu) as potential confounders.

RESULTS

Elevated and monotonically increasing mortality risks were observed for kidney cancer, chronic renal diseases, and multiple myeloma, and the association with internal uranium absorbed organ dose was statistically significant for multiple myeloma. Adjustment for potential confounders had minimal impact on the risk estimates.

CONCLUSION

Kidney cancer, chronic renal disease, and multiple myeloma mortality risks were elevated with increasing internal uranium absorbed organ dose. The findings add to evidence of an association between internal exposure to uranium and cancer. Future investigation includes a study of cancer incidence in this cohort.

Mortality in a combined cohort of uranium enrichment workers

OBJECTIVE

To examine the patterns of cause-specific mortality and relationship between internal exposure to uranium and specific causes in a pooled cohort of 29,303 workers employed at three former uranium enrichment facilities in the United States with follow-up through 2011.

METHODS

Cause-specific standardized mortality ratios (SMRs) for the full cohort were calculated with the U.S. population as referent. Internal comparison of the dose-response relation between selected outcomes and estimated organ doses was evaluated using regression models.

RESULTS

External comparison with the U.S. population showed significantly lower SMRs in most diseases in the pooled cohort. Internal comparison showed positive associations of absorbed organ doses with multiple myeloma, and to a lesser degree with kidney cancer.

CONCLUSION

In general, these gaseous diffusion plant workers had significantly lower SMRs than the U.S.

POPULATION

The internal comparison however, showed associations between internal organ doses and diseases associated with uranium exposure in previous studies. Am. J. Ind. Med. 60:96-108, 2017. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.