Influence of Flow on Abiotic and Biotic Reactivity of CL--20 (hexaanitrohexaazaiso-wurtzitane) (PNNL Scope # 42095)
EMSL Project ID
8218
Abstract
Mechanistic studies of surface bound natural FeII , or surface bound biogenically or chemically reduced Fe on the degradation kinetics of CL-20 (hexaanitrohexaazaiso-wurtzitane) are being conducted as part of a SERDP project at PNNL (Jim Szecsody, PI). Experiments will be conducted with three solids, an FRC saprolite sediment, 2-line ferrihydrite and magnetite. Work will start with the sediment and proceed with the ferrihydrite and magnetite in that order. Experiments will be conducted in three stages, all of which require a low O2 working environment (< 1-2 ppm). Stage 1: Set up and Fe reduction. In the anaerobic chamber experiments will be set up using 50 ml test tubes containing sediments or ferrihydrite or magnetite. Oxygen free (sparged) electrolyte (10 mM CaCl2), and Pipes buffer (30mM) adjusted to pH 7 will be added and sealed with septa closures. To these either a solution of dithionite or anaerobically grown CN 32 (plus lactate) will be added to start the iron reduction. Samples will either be removed from the chamber and placed in an incubator or remain in the chamber mounted on a small sample-rotator holding 10 tubes. At regular time intervals samples will be taken from the chamber or incubator and frozen. Stage 2: CL-20 degradation. Thawed samples will reintroduced into the chamber. To a subset of these samples O2 free CL-20 (sparged) will be injected and then returned to the incubator or the rotator. At regular intervals in the chamber solution samples will be withdrawn from tubes of this subset, filtered and analyzed for aqueous FeII,III and CL-20 and its degradation products. At the end of this experiment the solid phase of this subset will be extracted with methanol (in chamber) and the extract analyzed for CL-20 and its degradation products to determine the quantity of sorbed CL-20 remaining on the solids. In the third stage the second subset of reduced samples that did not have CL-20 added, will be analyzed for aqueous and solid phase FeII,III , the latter by injecting 0.5 or 5 M HCl (O2 free) into sample tubes and rotating for 2 hr and 7 days, respectively, for the 0.5 and 5 M HCl extractions. Finally, with respect to the magnetite experiments, it is our intention to do the final stage of grinding of this mineral (to a mesh between 200 and 300 um) in the anaerobic chamber in such a manner to minimize dust. A small agate mortar and pestle will be used to do hand grinding. A small diameter set of three hand shaken sieves will be used to obtain the desired size fraction. Grinding and sieving will be done inside a plastic bagin the chamber to limit spread of dust. If static electricity creates a containment problem in the bag then this will have to be done elsewhere. The reason for doing this in the chamber is to minimize the exposure of the freshly exposed surfaces of this FeII + FeIII mineral to O2 and thus oxidation the surface FeII .Thus we need access to a atmospheric chamber in EMSL 1410 and possibly the incubator in 1544.
Project Details
Project type
Exploratory Research
Start Date
2004-04-02
End Date
2007-06-03
Status
Closed
Released Data Link
Team
Principal Investigator