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pure polymer and its nanohybrid are fabricated by irradiating with
swift heavy ions (SHI) (Ag+) having 140 MeV energy followed
by selective chemical etching of the amorphous path, caused by the
irradiation of SHI, to generate nanochannels of size ∼80 nm.
Grafting is done within the nanochannels utilizing free radicals generated
from the interaction of high-energy ions, followed by tagging of ionic
species to make the nanochannels highly ion-conducting. The uniform
dispersion of two-dimensional nanoparticles better controls the size
and number density of the nanochannels and, thereby, converts them
into an effective membrane. The nanoparticle and functionalization
induce a piezoelectric β-phase in the membrane. The functionalized
membrane removes the radioactive nuclide like 241Am+3 (α-emitting source) efficiently (∼80% or 0.35
μg/cm2) from its solution/waste. This membrane act
as a corrosion inhibitor (92% inhibition efficiency) together with
its higher proton conduction (0.13 S/m) ability. The higher ion-exchange
capacity, water uptake, ion conduction, and high sorption by the nanohybrid
membrane are explored with respect to the extent of functionalization
and control over nanochannel dimension. A membrane electrode assembly
has been fabricated to construct a complete fuel cell, which exhibits
superior power generation (power density of 45 mW/cm2 at
a current density of 298 mA/cm2) much higher than that
of the standard Nafion, measured in a similar condition. Further,
a piezoelectric matrix along with its anticorrosive property, high
sorption characteristics, and greater power generation makes this
class of material a smart membrane that can be used for many different
applications.
Studies on isotopic and ion-exchange kinetics of mercury ions in Nafion-117 membrane have been carried out with (203)Hg radiotracer in the presence of Cl(-) and NO(3)(-) in solution. The results of isotopic-exchange kinetics indicate that mercury ions diffuse into the membrane as monovalent cation from HgCl(2) solution while as divalent ion from Hg(NO(3))(2) solution. The studies on the kinetics of ion exchange of Hg(2+) with Na(+) follow the prediction of the Nernst-Planck equation when NaNO(3) is used as an external salt solution. The Nernst-Planck equation fails to predict the kinetics when NaCl is used as an external salt solution, indicating that the complexation of Cl(-) with Hg(2+) in the membrane influences the kinetics. Permeation studies using (203)Hg and (36)Cl radiotracer between two HgCl(2) solutions show that the permeability coefficients of mercury and chloride ions are the same, indicating the cotransport of mercury and chloride ions through the membrane. Ion-exchange equilibrium studies using a mixture of HgCl(2) and HNO(3) solution were carried out to ascertain the species transporting through the membrane. The equilibrium sorption of mercury in the membrane shows the uptake of an ionic species, presumably HgCl(+), not a neutral salt. The speciation diagrams, calculated as a function of pH, show wide divergence of species present in HgCl(2) and Hg(NO(3))(2) solution and explain the difference in membrane transport behavior for HgCl(2) and Hg(NO(3))(2) solution. The results show that any ion-exchange-membrane-based separation of Hg(2+) needs careful consideration regarding the anions present in the solution, as it influences the speciation of mercury and hence its transport behavior through the membrane.
Thin poly(bis[2-(methacryloyloxy)ethyl] phosphate) grafted glass has been used for selective preconcentration and source preparation for alpha spectrometry of Pu(iv) ions.
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