Development of an eco-friendly method to convert life expired composite propellant into liquid fertilizer

Large quantity of composite propellants is produced as waste due to life expiry of missiles/rejection of propellant lots during manufacturing. The environmental protection agency does not allow the hazardous materials for open burning/open detonation. Therefore, a systematic study has been carried out to develop a method for the disposal of composite propellant into liquid fertilizer without affecting the environment. In this study, propellant compositions were digested in dilute nitric acid followed by neutralization with 5M KOH solution to get precipitated out aluminium as aluminium hydroxide and finally the obtained liquid was treated with orthophosphoric acid for further neutralization. The liquid fertilizer, thus, obtained was characterized for nitrate and phosphate content using ion chromatography while ICP-AES was used for the estimation of potassium, aluminium and other noxious metallic elements such as Pb, Cd, As, Cr, Cu, Ni and Zn. The analyses data indicate that liquid fertilizer is free from aluminium and noxious metallic elements while ratio of nitrogen, phosphorous and potassium are close to the Indian NPK value.