US Army tests chemical weapons destruction
9 Oct 2000
Aprocess developed by AEA Technology could be used to destroy the US's stockpile of chemical weapons. Based around the oxidising power of silver ions, the process is currently being tested by the US Army.
The process, called SilverII, was originally developed to destroy organic waste generated by the nuclear industry. A demonstration plant was set up at Dounreay in the late 1980s, followed by another at the Chemical and Biological Defense Establishment at Porton Down. Tests there have proved that the system can destroy a variety of chemical weapons including the nerve gases Sarin and VX, blistering agents such as mustard and Lewisite, as well as explosives such as TNT and RDX.
SilverII is a fairly simple electrochemical process which generates Ag++ ions, a strongly-oxidising species which will break down virtually any organic or chemical material into carbon dioxide, insoluble organic salts and water. The waste material is mixed with a solution of nitric acid and silver nitrate, which is pumped into the anolyte circuit of a standard industrial membrane electrochemical cell. The electrochemical current transforms the stable Ag+ ions in the nitrate solution into highly reactive Ag++, which reacts with the waste molecules as soon as it is formed. This reaction reduces the ions back to Ag+, which passes through the membrane into the catholyte side of the cell for recycling.
A continuous hydrocyclone removes insoluble salts from the anolyte, while off-gases are removed through a condenser. Any potentially harmful gases from the reaction, notably NOx from the balancing reaction on the cathode side of the cell, are removed through scrubbers, and the resulting vapours — after testing to confirm that no harmful material has survived — pass through an activated carbon filter before being vented to the atmosphere.
The US Army is currently evaluating SilverII, along with four other processes, as part of its drive to destroy its 30 000tonne stockpile of chemical warfare agents under the Chemical Weapons Convention. The most successful process will be used to destroy stockpiles of Sarin and VX at Blue Grass, Kentucky, and mustard gas munitions at Pueblo, Colorado.
