Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Aqueous”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Impact of Structural Defects and Hydronium Ion Concentration on the Stability of Zeolite BEA in Aqueous Phase

The presence of fluoride anions in the synthesis gel leads to zeolite BEA with high hydrothermal stability. This longer lifetime is caused by a lower concentration of internal silanol defects that are sites of the initial framework hydrolysis eventually destroying the lattice structure. The lifetime of these zeolites was the higher the lower the concentration of framework bridging hydroxyl groups that form hydronium ions was. While lattice hydrolysis was initiated at defect sites in all cases, the role of defects became less important as the concentration of hydronium ions increased. At higher concentration of hydrated hydronium ions, the presence of water associated with the hydrated hydronium ions limits the useful lifetime of zeolite catalysts in water. For such materials, the selective hydrophobization of the external surface extends the lifetime. Acknowledgments: S.P. and M.A.D. acknowledge support by the Materials Synthesis and Simulation Across Scales (MS3 Initiative) conducted under Laboratory Directed Research & Development Program at PNNL. H.S. and H.W. were supported by the Chemical Transformation Initiative (CTI) conducted under Laboratory Directed Research & Development Program at PNNL. J.A.L. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

Prodinger, Sebastian↗
DOE OSTI2022

Removal of iodine (I- and IO3-) from aqueous solutions using CoAl and NiAl layered double hydroxides

The treatment of radioactive iodine released from nuclear power plants and radiological waste disposal sites is of great concern due to its high mobility and toxicity. In particular, iodide (I-) and iodate (IO3-) are the major iodine species of concern under various pHs and groundwater conditions. Herein, CoAl and NiAl layered double hydroxides (LDHs) were synthesized by a hydrothermal method and investigated to identify the removal mechanisms and efficiencies of both I- and IO3-. Both CoAl and NiAl LDHs exhibited rapid iodine removal processes within 20 min, following the pseudo-second-order model via ion-exchange with parent NO3- anion in the LDHs. The CoAl LDH’s maximum sorption capacities for I- and IO3- were about 1.67 and 2.16 mmol g-1, respectively, whereas for the NiAl LDH, these were about 2.10 and 2.26 mmol g-1, and they followed the Langmuir isotherm model. Interestingly, both the CoAl and NiAl LDHs showed a preferential ion-exchange affinity for IO3- over I-, which was attributed to the structural similarity of the IO3- and NO3- as well as new formation of secondary Co(or Ni)(IO3)2·2H2O phases. In addition, a desorption study indicated that the selectivity order was SO42- = IO3- = OH- > HCO3- > Cl- > NO3- = I- and demonstrated the higher retention of the IO3- than I- anion. This study provides insights into promising iodine sorbents and the different removal mechanisms of I- and IO3- using CoAl and NiAl LDHs.

Kang, Jaehyuk↗
DOE OSTI2015

Structural rearrangement and dispersion of functionalized graphene sheets in aqueous solutions

Surfactants are widely used for dispersing graphene and functionalized graphene sheets (FGS) in colloidal suspensions, but there have been few studies of the structure of the dispersed graphene-surfactant complexes in suspension and of their time evolution. Here, we combine experimental study of efficiencies of ionic surfactants/polymers in suspending FGS in water with characterization using atomic force microscopy, small angle neutron scattering, and molecular simulations to probe the detailed structures of FGSs. A systematic study of FGS dispersions using ionic surfactants with varying chain lengths revealed that the effective charge density of surfactant layer defines the concentration of dispersed FGS while the strength of interfacial binding defines the stability of graphene dispersion over long time aging. Ionic surfactants with strong interfacial binding and large molecular weight increase the dispersing power by over an order of magnitude.

36 MATERIALS SCIENCE↗