Moringa fruit shell derived carbon-hydrogel functional composite for sustainable pharmaceutical remediation and triboelectric energy harvesting

Abstract

The development of sustainable, multifunctional materials that simultaneously address environmental remediation and energy generation remains a critical challenge. We developed a biodegradable, cost-effective hydrogel composite, namely Moringa fruit shell-derived activated carbon (MFAC) incorporated into sodium alginate-polyvinyl alcohol (SA-PVA) hydrogel beads (MFAC@SA-PVA/HB). Structural and physicochemical characterization using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (P-XRD), and X-ray photoelectron spectroscopy (XPS) confirmed the formation of a hierarchically porous hybrid network with enhanced structural stability due to polymer-carbon interactions. The hydrogel exhibited excellent adsorption performance toward fluorescein sodium drug (FSD), achieving a maximum Langmuir adsorption capacity of approximately 200 mg g⁻¹. Adsorption followed the nonlinear pseudo-second-order kinetic model, indicating chemisorption-dominated uptake, with an optimum adsorption capacity of approximately 186.52 mg g⁻¹ at pH 3.5. The adsorbent retained high removal efficiency over ten consecutive adsorption-desorption cycles, demonstrating excellent reusability and stability, and its applicability was successfully validated using real water samples and industrial effluents. Furthermore, the spent MFAC@SA-PVA/HB was upcycled as a triboelectric nanogenerator (TENG), delivering an output voltage of approximately 350 mV, current of 900 nA, and a maximum power density of 1.87 mW cm⁻², enabling capacitor charging and light-emitting diode operation. Green Analytical Procedure Index (GAPI) and Analytical GREEnness (AGREE) assessments confirmed the sustainability of the proposed approach, demonstrating a sustainable dual-functional platform for water remediation, waste valorization, and energy harvesting.