Remediate with carbonate

28 August 2012Chemistry World

I was interested in the article ‘Destroying war’s chemical legacy’ because, when working on the thorium molten salt nuclear reactor programme at the Oak Ridge National Laboratory, US, in the early 1960s, I attended a lecture on a simple molten salt procedure for destroying waste materials. Molten salt oxidation (MSO) was used in the 1960s for 15 years but rejected because paper, plastic and cotton were incompletely oxidised: molten carbonate was considered the catalyst. In the 1980s, at the University of Leeds, we oxidised UO₂ to uranate, using air in molten carbonates. We showed that oxygen dissolved chemically in molten carbonate, forming active peroxide and superoxide ions and their concentration could be maintained by adding nitrate (as a catalyst), completely oxidising paper, plastic and cotton, and ceramic UO₂. After 50 publications in 10 years, we published an alternative process for reprocessing spent nuclear fuel, using our CEMSO (catalyst enhanced molten salt oxidation).

The US Army reported in the 1960s that chemical warfare agents, including sarin, were destroyed in molten carbonate with an efficiency of >99.9999% and similarly for polychlorinated biphenyls, trichlorobenzene, ion exchange resins, and old explosives, and with >99.9% efficiency for Pu contaminated waste. Why has all this been forgotten? I heard of the Chemical Weapons Convention some years ago and spoke to the former research director at the Nuclear Decommissioning Authority’s site at Dounreay, UK, who agreed MSO was excellent and regretted it was too late to be adopted for destroying chemical weapons but informed me that the Japanese have tons of arsenical agents too volatile to tackle. We have shown that when As(iii) is oxidised by MSO to As(v) it is stable up to 800°C in molten carbonate, and we use 550°C for CEMSO. I await a phone call.

T R Griffiths FRSC

Leeds, UK