Tributylphosphate (TBP) is a highly toxic, environmentally persistent, and difficult-to-dispose-of chemical which finds extensive use in a variety of industries, such as in flame retardants and plasticizers. Its most notable application is as a means of extracting valuable actinide metals such as uranium for nuclear power applications from ores or waste through the so-called PUREX process.
No alternatives to TBP currently exist. Previous attempts at TBP disposal include incineration, treatment with strong acids and bases at high temperatures under reflux conditions, destruction with radiation, and the use of biological organisms to metabolize the chemical. All of these methods are generally not cost-effective or carry other concerns.
The International Atomic Energy Agency expects worldwide nuclear power usage to increase by 17% to 94% by the year 2030. There will be an increasing demand for this hazardous material for the foreseeable future. Green disposal and neutralization methods targeting this chemical are necessary.
Livermore Laboratory researchers have developed a methodology for degradation of TBP using an inexpensive, readily available, and environmentally friendly salt, potassium iodide (KI), in a similarly inexpensive, abundant, and green solvent dimethylsulfoxide (DMSO) to efficiently convert TBP to the potassium salts of dibutylphosphate (DBP) and monobutylphosphate (MBP) The reaction is carried out at a lower temperature than has been reported for any other chemical method, reducing the cost of operation associated with elevated temperatures.
Incineration and alkaline hydrolysis at high temperature are methods of disposal that are not cost effective. LLNL's methodology employs the inexpensive salt potassium iodide (KI) towards the conversion of TBP into the more water-soluble potassium dibutylphosphate (DBP) and monobutylphosphate (MBP) salts. These byproducts may be further processed using previously established techniques; thus represents the first step in the overall degradation of TBP to inorganic phosphate in the efficient and environmentally friendly disposal of an extremely hazardous industrial chemical.
The main potential use of this method is for the disposal of TBP used in a variety of industrial processes (particularly in refining of nuclear waste). Such a method might also have use in processing other organophosphate waste.
A manuscript has been submitted to the journal Analytical Chemistry Letters.
LLNL has filed U.S. Patent Application No. 15/191431 “Halide-Mediated Dealkylation of Phosphotriesters”.