Investigation on stripping-down TNT from waste munitions by supercritical CO₂ fluid extraction under low temperature conditions

The traditional methods of waste munitions treatment are expensive and also have potential risks during the treatment process. The supercritical fluid extraction technique has been a rapidly developing technique in the chemical industry in recent years. CO₂ is used as the solvent, which has some advantages, such as low pollution, low cost, good chemical stability and can be operated under low temperature conditions. This research explored the feasibility of reclaiming TNT from waste munitions by supercritical CO₂ fluid extraction. It was found interestingly that the melting point of TNT can be lowered in supercritical CO₂ fluid. Therefore, the melting process of TNT was observed under different temperature and pressure conditions to determine the best operating conditions for stripping-down TNT from waste munitions. Afterwards, simulated warheads with weight loadings of 60 g, 500 g and 1 kg of TNT were prepared and stripping-down tests from the simulated warheads were carried out using supercritical CO₂ fluid at temperatures lower than the normal melting point of TNT. The results showed that TNT could be completely removed from the simulated warheads and the optimum operating conditions were determined as 55 °C and 25 MPa. This study will contribute to the feasibility evaluation of stripping-down TNT-based high explosives.