4 research outputs found
Improved Catalytic Activity and Stability Using Mixed Sulfonic Acid- and Hydroxy-Bearing Polymer Brushes in Microreactors
Sulfonic acid-bearing polymer brushes
were grown on the inner walls
of continuous flow glass microreactors and used in the acid-catalyzed
hydrolysis of benzaldehyde dimethyl acetal as a test reaction. Randomly
1:1 mixed polymer brushes of poly-3-sulfopropyl methacrylate (PSPM)
and poly-2-hydroxyethyl methacrylate (PHEMA) showed a 6-fold increase
of the TOF value compared to the solely PSPM-containing microreactor.
This remarkable improvement is attributed to the cooperative stabilizing
effect of proximal OH groups on the active sulfonic acid moieties
within the brush architecture. In fact, the rational mixing of SPM
with methyl methacrylate (MMA) as an OH-free comonomer caused a drop
in the activity of the resulting catalytic platform. A 5-fold increase
of the TON of the 1:1 PSPM–PHEMA versus the PSPM homopolymer
brush systems additionally demonstrates the substantial increase in
the stability of the mixed brushes catalytic platform, which could
be continuously run over 7 days without significant loss of activity.
The 1:1 PSPM–PHEMA mixed brush catalytic system also showed
a good activity in the deprotection of 2-benzyl tetrahydropyranyl
ether
Insight into the Complexation of Actinides and Lanthanides with Diglycolamide Derivatives: Experimental and Density Functional Theoretical Studies
Extraction of actinide
(Pu<sup>4+</sup>, UO<sub>2</sub><sup>2+</sup>, Am<sup>3+</sup>) and
lanthanide (Eu<sup>3+</sup>) ions was carried
out using different diglycolamide (DGA) ligands with systematic increase
in the alkyl chain length from <i>n</i>-pentyl to <i>n</i>-dodecyl. The results show a monotonous reduction in the
metal ion extraction efficiency with increasing alkyl chain length
and this reduction becomes even more prominent in case of the branched
alkyl (2-ethylhexyl) substituted DGA (T2EHDGA) for all the metal ions
studied. Steric hindrance provided by the alkyl groups has a strong
influence in controlling the extraction behavior of the DGAs. The
distribution ratio reduction factor, defined as the ratio of the distribution
ratio values of different DGAs to that of T2EHDGA, in <i>n</i>-dodecane follows the order UO<sub>2</sub><sup>2+</sup> > Pu<sup>4+</sup> > Eu<sup>3+</sup> > Am<sup>3+</sup>. Complexation
of Nd<sup>3+</sup> was carried out with the DGAs in methanol by carrying
out
UV–vis spectrophotometric titrations. The results indicate
a significant enhancement in the complexation constants upon going
from methyl to <i>n</i>-pentyl substituted DGAs. They decreased
significantly for DGAs containing alkyl substituents beyond the <i>n</i>-pentyl group, which corresponds to the observed trend
from the solvent extraction studies. DFT-based calculations were performed
on the free and the Nd<sup>3+</sup> complexes of the DGAs both in
the gas and the solvent (methanol) phase and the results were compared
the experimental observations. Luminescence spectroscopic investigations
were carried out to understand the complexation of Eu<sup>3+</sup> with the DGA ligands and to correlate the nature of the alkyl substituents
on the photophysical properties of the EuÂ(III)-DGA complexes. The
monoexponential nature of the decay profiles of the complex revealed
the predominant presence of single species, while no water molecules
were present in the inner coordination sphere of the Eu<sup>3+</sup> ion
Highly Efficient Extraction Chromatography Resin Containing Hexa‑<i>n</i>‑Octyl Nitrilotriacetamide (HONTA) for Selective Recovery of Plutonium from Acidic Feeds
An extraction chromatography
resin was prepared by impregnating hexa-n-octyl nitrilotriacetamide
(HONTA) on chromosorb-W. This resin shows very efficient performance
for selective separation of Pu4+ over other actinides like
uranium and americium. The distribution coefficient for Pu4+ (at 3 M HNO3) was on the order of 104 mL/g,
with separation factors of >103 for other actinides.
The
extraction kinetics for Pu4+ was slow and took 20 min of
shaking for reaching the equilibrium conditions and followed both
the film diffusion and the intraparticle diffusion kinetic models.
The Pu4+ sorption on the resin followed the Langmuir monolayer
model with a sorption energy of 11.2 kJ/mol. The maximum Pu4+ loading capacity on the resin was 58.2 mg/g resin, which corresponds
to 1:1 Pu/ligand complex formation. Excellent column performance was
observed for selective separation of Pu4+ from a mixture
of Pu, Am, and U in a 3 M HNO3 solution
Solvent Optimization Studies for a New EURO-GANEX Process with 2,2’-Oxybis(<i>N,N</i>-di-<i>n</i>-decylpropanamide) (mTDDGA) and Its Radiolysis Products
The diglycolamide 2,2’-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) is being studied as an extractant for actinides and lanthanides in the European Grouped Actinide Extraction (EURO-GANEX) process. The aim is the development of a more simplified process using a single extractant instead of a mixture of extractants used in the current EURO-GANEX process. This work presents solvent optimization studies of mTDDGA, with regards to the extraction characteristics of the different diastereomers of mTDGA and of mixed diastereomer solutions. Also radiolysis behavior has been studied by irradiation of solvent extraction systems in a gamma irradiation facility using 60Co. The availability of irradiated organic solutions made it possible to gain valuable insights into the plutonium loading capacity after gamma-irradiation of the solvent up to 445 kGy and to quantify degradation compounds. Solvent extraction characteristic of the major degradation compounds themselves were determined. Like other methylated diglycolamides, we found a remarkable difference in extraction of up to two orders of magnitude between the two diastereomers. High plutonium loading (36 g L−1) is feasible using this single extractant, even after absorbing a dose of 445 kGy. This remarkable observation is possibly promoted by the presence of the main degradation compound which extracts plutonium verywell.</p