Effect of gamma irradiation on thermal decomposition of tri-iso-amyl phosphate–nitric acid biphasic systems

Abstract

The thermal decomposition behaviour of tri-iso-amyl phosphate (TiAP)–nitric acid biphasic (organic and aqueous phases) systems was investigated using an adiabatic calorimeter. Experiments were conducted in a closed air ambience under heat–wait–search mode. Neat TiAP, n-dodecane (n-DD) and 1.1 mol dm−3 TiAP solution in n-DD were irradiated using a 60Co source and used for the thermal decomposition studies. These studies established that neat (unirradiated) TiAP is stable up to 540 K, and above this temperature, it undergoes exothermic decomposition, whereas the irradiated TiAP exhibits decomposition beyond 490 K in the absence of nitric acid. However, in the presence of nitric acid, TiAP decomposes at much lower temperature (384–499 K) with the formation of incompressible gases and viscous black liquid. The exothermic nature of TiAP decomposition in the presence of nitric acid strongly depends on the acid concentration and amount of acid present in the mixture. Thermo-kinetic parameters were derived for the decomposition reactions wherever possible and presented for the first time. The decomposition enthalpies were found to be lower for irradiated TiAP system compared to unirradiated system under identical conditions.