The U.S. Army's experience with neutralization of the nerve agent GB has confirmed some of the potential virtues as well as the practical problems associated with this technology. In an extensive field program carried out at the Rocky Mountain Arsenal from 1973 to 1976, 4,188 tons of GB were hydrolyzed successfully (Flamm et al., 1987). The nerve agent was treated with a large excess of aqueous sodium hydroxide to produce a water solution of inorganic salts and organic compounds. The solutions were evaporated, and the solid residues were deposited in a hazardous waste landfill. With hindsight and better analytical capabilities, it appears that the amount of solid waste could have been substantially reduced by working with a much smaller ratio of alkali to GB. In addition to the U.S. Army experience with hydrolysis of GB, various neutralization processes have been used to destroy multi-ton quantifies of the agent in Great Britain, Canada, the Soviet Union, and most recently, Iraq. Overall chemical hydrolysis has much to recommend it for destruction of bulk quantities of agent GB.
In contrast to the large-scale use of neutralization to destroy GB, the experience with hydrolysis of nerve agent VX and the various mustard agents is largely confined to laboratory- and pilot-scale studies. A major problem is that these agents, in contrast to GB, are much less soluble in water and react slowly under neutral or alkaline conditions. Several approaches to deal with this problem have been explored (Yang et al., 1992). For agent VX, aqueous solubility is greatly increased by working in acidic solution because the acid protonates the amine function of the agent to form a soluble salt:
Although both acid and base catalyze the hydrolysis of the P—S and P—O bonds, these reactions are slow and incomplete at ambient temperature. At elevated temperature (75-90ºC), alkaline hydrolysis detoxifies VX in less than one hour (NRC, 1993a).