tions for permit modifications are also shown in the table. The regulations generally specify that the carbon will require extractive analysis to confirm that agent concentration(s) are below the respective WCLs or PCCs.
Although all three chemical agents are strongly adsorbed on coconut shell activated carbon, they all react with the moisture that is also adsorbed on the carbon to form the expected hydrolysis products. In 2007, several carbon samples from Banks 1 and 2 of the MDB HVAC filter unit at ANCDF were analyzed for residual GB and VX at both government and contractor surety laboratories.
These analyses verified that the agents GB and VX decompose by hydrolysis with the adsorbed water on the carbon. The amount of GB that must have been adsorbed on Bank 1 carbon during processing of GB munitions in the MDB is evidenced by the 13 wt percent of its hydrolysis product, isopropyl methylphosphonic acid (IMPA), which was found on the carbon by solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR). In comparison, only a trace amount of the VX hydrolysis product, ethyl methylphosphonic acid (EMPA), was found on carbon from Bank 1. This small amount of the hydrolysis product is attributed to the low volatility of VX. Extractive analysis of HVAC filter unit carbon samples from NECDF by the system contractor laboratory indicated the presence of volatile VX impurities, hydrolysis by-products, and degradation products of the aminothiol group. At this time, no MDB HVAC carbon sample exposed to mustard agent HD from a chemical agent disposal facility is available for laboratory analysis.
The shipping of agent-exposed carbon to off-site disposal facilities will require determination of the loading of agent on the carbon on a mass basis (mass of agent per mass of carbon). For parts-per-billion levels of detection of residual agents on carbon, solvent extraction of the adsorbed phase from the carbon sample followed by gas chromatography/mass spectrometry (GC/MS) analysis is being pursued. The Bank 1 carbon removed at ANCDF was analyzed by this method at Southwest Research Institute to determine the amounts of GB and VX remaining on the carbon. VX was below the WCL, but GB was above it. The GB result has been interpreted as a sign that GB re-forms from the hydrolysis products in the solvent during the extraction process. A way was found to limit this re-formation to ~6 ppb, but this modification to the standard method is not considered valid until other laboratories have reproduced the results. Early (unvalidated) measurements on the ANCDF Bank 1 carbon indicate that the residual GB (~129 ppb) is above the WCL limit (20 ppb), which means the carbon will not be transportable under the present permit. However, carbon containing GB at more than 20 ppb could be transported off-site if the transportation risk assessment (TRA) approved by state regulators and procedures was implemented to satisfy the bounding TRA values. These values are a function of accidental release scenarios assumed in the assessment and the frequency established for such release scenarios.
In response to the third bullet in the statement of task for this study, the committee surveyed the common industrial practices for managing activated carbon. In commercial and industrial applications, activated carbon finds extensive use as an adsorbent for removal of a wide range of contaminants from liquids and gases. Demand for activated carbon in the United States was 363 million pounds in 2005, split approximately equally between granulated activated carbon and powdered activated carbon. The activated carbon used in chemical agent disposal facilities is granulated. Activated carbon is also used to adsorb a product such as a solvent from a process stream. In such applications, the adsorbed product is subsequently desorbed on-site for reuse. This last step, known as “carbon regeneration,” differs from “carbon reactivation,” which is a treatment process whereby adsorbed materials (adsorbates) on the carbon are destroyed and the structure of the activated carbon is restored for reuse. Reactivation is carried out in either a rotary kiln or multiple hearth furnaces where the carbon is heated in the presence of steam to 1800°F.
There are essentially three treatment and disposal methods used for treating activated carbon from commercial operations: (1) reactivation, (2) landfill, and (3) incineration. If carbon from commercial industrial operations has been reactivated, vendors offer two options. One is to return the reactivated carbon to its former user. The other is to combine it with reactivated carbon from other sources and resell it. Reactivation is attractive to industrial users principally because it is less costly than disposal and purchase of freshly made activated carbon.
When varying amounts of mercury were discovered in the mustard agent HD/HT ton containers at TOCDF, PBCDF, and UMCDF, CMA was required to develop a strategy to prevent emission of mercury during the incineration of HD/HT. Unlike agent, mercury persists in one form or another in the offgas leaving the PAS units of the incinerators. Testing results have shown