From Waste Tea to Carbon Rocket Fuels through a Piranha Solution-Mediated Carbonization Treatment

Author(s): Georgios Asimakopoulos, Dimitrios Moschovas, Apostolos Avgeropoulos, Athanasios B Bourlinos, Iosif Tantis, Veronika Sedajová, Ondrej Tomanec, Constantinos E Salmas, Dimitrios Gournis, Michael A Karakassides

In a previous work we have demonstrated the carbonization of biomass waste, such as stale bread, spent coffee and cardboard, in piranha solution towards the formation of hypergolic carbons that could be exploited as solid fuels in rocket engines. These cases simply aimed to provide some interesting examples of waste valorization towards a new class of carbon-based rocket fuels rather unique to the piranha solution treatment. In an effort to further strengthen this concept with additional examples herein we report the carbonization of waste tea in piranha solution towards the formation of hypergolic carbons at decent yield. Likewise bread, coffee and cardboard waste, spent tea is also produced in large quantities worldwide every year, thus meriting further attention in this context. Consistently with the previously reported results, the piranha solution-mediated carbonization of waste tea produces carbon nanosheets that spontaneously ignite upon contact with fuming nitric acid HNO3 at ambient conditions. Interestingly, intercalation of the nanosheets with certain ignitable molecules further boosts carbon hypergolicity upon contact with fuming nitric acid HNO3. These findings come to confirm the versatile character of the method in diverting biomass waste into valuable energetic carbons by piranha solution.