Engineering topics
Publications and source records attributed to Mo, Kai-For.
With the opioid epidemic at an all-time high, new synthetic opioids continue to emerge. To assist first responders in identifying new chemical variants, PNNL is working to expand spectral libraries of field-portable chemical detection instruments.
Much is still unknown about the mechanisms and rates of environmental degradation of organophosphorous pesticides and agents. In this study we focus on the degradation of one organophosphorous compound, namely solid methyl phosphonic acid anhydride [CH3P(O)OHOP(O)OHCH3, MPAN] and its rate of conversion to methyl phosphonic acid (MPA) via heterogeneous hydrolysis. Pure MPAN was synthesized and loaded in open sample cups placed inside exposure chambers containing saturated salt solutions to control the relative humidity (RH). The reaction was monitored in the sample cup at various times using both infrared hemispherical reflectance (HRF) spectroscopy and Raman spectroscopy. Calibrated HRF and Raman spectra of both pure reagents as well as gravimetrically prepared mixtures were used to quantify the concentrations of MPAN and MPA throughout the reaction. Results show that both HRF and Raman spectroscopies are convenient non-invasive methods for detection of solid chemicals. The MPAN degradation rate displayed a very strong dependence on relative humidity: At room temperature the reaction showed 50% conversion of the MPAN in 761 ± 54 hours at 33% RH, 33 ± 4 hours at 43% RH, 17 ± 2 hours at 54% RH and just 7 ± 1 hours at 75% RH. Although MPAN hydrolysis is a second-order reaction, the 33 and 43% RH data, at early reaction times, could be fit with a zeroth order reaction, indicating water vapor and MPAN concentrations were not initially rate controlling. The 54 and 75% RH experiments showed significant deliquescence and decay data could only be fit assuming multiple reactions, implying chemical and/or physical processes partially controlled the hydrolysis rate, in contrast to a single process at low relative humidity.
Detecting chemical agents in outdoor environments such as a battlefield is made challenging by not only the spurious signatures from background chemicals and surfaces (e.g. asphalt, dirt, concrete), but also by the chemical transformation of the actual agents. The change of CW agents to other species can be catalyzed by other chemicals present in the scene, by different substrates, as well as by local weather conditions. Some of the final environmental transformation products are known (e.g. for the G agents methylphosphonic acid), but many of the intermediate chemical states are not, nor are the rates of transformation to the other intermediates or the end products. In this study we have made preliminary optical investigations into the degradation products of a G-agent intermediate, namely methylphosphonic anhydride and its rate of conversion to the more stable methylphosphonic acid. Using infrared and Raman spectroscopies, we have found that the relative humidity (RH) greatly affects the rate of change and we report first results from these studies.
This report summarizes the work of evaluating the chemical stability of phosphoramidic acid, N-N-diethyl-, bis(2-ethylhexyl) ester under the Solvent Exchange LDRD project, as a potential solvent exchange chemistry and analog to solvent exchange chemistries used in the TALSPEAK and ALSEP processes as alternatives to the use of tri-butyl phosphate in the PUREX process.
At PNNL, we have developed a completely new class of synthetic biomimetic sequence-defined polymers based on triazine chemistry, which we call TZPs. PNNL's new polymers offer the opportunity to achieve similar functions to natural macromolecules; specifically we designed and synthesized a diversity of test molecules for antimicrobial activity. Antimicrobial activity against a variety of wild type and drug resistant pathogens was found.