Recycled nitro-based composites as adsorbents for efficient removal of methylene blue

In the quest for eco-friendly wastewater treatment, an attempt has been made to explore recycled nitro-based waste energetic materials (WEMs), as novel adsorbents, and repurposing them for the removal of methylene blue (MB) dye from wastewater. The adsorption performance was evaluated for both the model MB dye solution and simulated textile wastewater containing MB. Among the tested WEMs (single-, double- and triple-base propellant), triple-base propellant (TBP) exhibited a superior adsorption capacity of 4.82 mg g^-1 and > 95% of MB dye removal in the model solution. Under simulated textile wastewater conditions, TBP achieved 4.60 mg g^-1 of adsorption capacity and 91.16% removal efficiency, affirming its real-world applicability. Comprehensive structural and morphological analyses revealed TBP's mesoporous structure, surface functionality and favourable surface charge (point of zero charge, pzc = 4.17), facilitating strong electrostatic interactions, thereby enhancing MB dye adsorption. Kinetic studies followed a pseudo-first-order model with rate constant k₁ = 0.011 min⁻¹ (for TBP), indicative of rapid dye uptake. GC-MS analysis revealed no detectable leaching of substances in the treated wastewater. Desorption studies demonstrated 80-90% adsorption efficiency over three cycles, indicating TBP's reusability. These findings demonstrate a sustainable waste-to-resource and cost-effective solution for wastewater treatment applications.