Adsorption of aqueous insensitive munitions compounds by graphene nanoplatelets

Mitigation strategies for potential environmental impacts of insensitive munition (IM) compounds, including 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), and methylnitroguanidine, (MeNQ) are being considered to enhance sustainability of current or potential IM formulations. Graphene nanoplatelets (GnPs) were investigated for adsorptive removal of each compound. GnPs were characterized to determine surface areas, along with particle size and zeta potential at different pH and ionic strength conditions. Adsorption kinetics and isotherm studies were conducted, comparing results against granular activated carbon (GAC). Ionic strength, pH, and temperature were adjusted to inform impacts on adsorptive behaviors and performance. The results indicated that GnPs adsorbed IM compounds more rapidly than GAC. Additionally, GnPs removed DNAN with greater capacity compared to GAC, likely due to π-π interactions. GnPs removed other compounds via van der Waals forces, while GAC exhibited greater adsorption capacities due to higher surface area. Although negative charges associated with GnPs and dissociated NTO species hindered adsorption, pH and ionic strength did not impact other compounds. Moreover, this study reports the first environmental treatment technique for MeNQ. Overall, these findings suggest that GnPs are a promising treatment technology for IM-laden waters, particularly those with compounds like DNAN where specific interactions enhance removal efficiency.