Processing of hazardous materials
is a crucial example where online
monitoring can significantly reduce operation risk, cost, and time.
This is particularly true in the case of the Hanford site, where nuclear
materials from the Cold War era are being processed for environmental
cleanup efforts. In exceedingly complex streams such as those at Hanford,
online and real-time monitoring can be challenging due to the complexity
of instrument signals. Further obstacles are imposed by the caustic
nature of processing streams, as well as the radiation damage inflicted
on instruments and probes. Online monitoring based on Raman spectroscopy
enables the detection of many Hanford tank species of interest. Nine
chemical species that comprise the majority of tank waste by volume,
including Al(OH)4
–, C2O4
2–, CO3
2–,
CrO4
2–, NO3
–, NO3
–, OH–, PO4
3–, and SO4
2–, were detected and quantified. Real-time analysis of Raman signal
allows for immediate quantification of target analytes and was successfully
accomplished through the use of chemometric models. Furthermore, irradiation
tests revealed that Raman monitoring systems can effectively continue
to operate even after receiving 1 × 107 rad of γ
dose. The online, real-time monitoring system developed here was successfully
used to simultaneously quantify nine target analytes in a real sample
collected from Hanford tank AP-105.
J. McFarlane, (a) N. D. Bull Ezell, (a) G. D. DelCul, (a) D. E. Holcomb, (a) K. Myhre, (a) A. Lines, (b) S. Bryan, (b) H. Felmy, (b) and B. J. Riley (b) (a) Oak Ridge National Laboratory (b) Pacific Northwest National Laboratory
Microfluidics
have many potential applications including characterization
of chemical processes on a reduced scale, spanning the study of reaction
kinetics using on-chip liquid–liquid extractions, sample pretreatment
to simplify off-chip analysis, and for portable spectroscopic analyses.
The use of in situ characterization of process streams
from laboratory-scale and microscale experiments on the same chemical
system can provide comprehensive understanding and in-depth analysis
of any similarities or differences between process conditions at different
scales. A well-characterized extraction of Nd(NO3)3 from an aqueous phase of varying NO3– (aq) concentration with tributyl phosphate (TBP) in dodecane
was the focus of this microscale study and was compared to an earlier
laboratory-scale study utilizing counter current extraction equipment.
Here, we verify that this same extraction process can be followed
on the microscale using spectroscopic methods adapted for microfluidic
measurement. Concentration of Nd (based on UV–vis) and nitrate
(based on Raman) was chemometrically measured during the flow experiment,
and resulting data were used to determine the distribution ratio for
Nd. Extraction distributions measured on the microscale were compared
favorably with those determined on the laboratory scale in the earlier
study. Both micro-Raman and micro-UV–vis spectroscopy can be
used to determine fundamental parameters with significantly reduced
sample size as compared to traditional laboratory-scale approaches.
This leads naturally to time, cost, and waste reductions.
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