Spongy carbon from inedible food: A step towards a clean environment and renewable energy

Abstract

The global challenges of access to clean water and energy continue to grow, prompting research into sustainable solutions. A promising approach involves the conversion of agricultural waste into high-porosity functional materials for both water purification and energy storage. This study explores the conversion of stale bread into spongy carbon materials, which were evaluated as adsorbents for the removal of cationic dyes and electrodes for supercapacitors. The physical and chemical properties of the material were characterized using standard techniques. In particular, activated carbon produced at 900 °C showed a balanced mixture of micropores and mesopores, with a high specific surface area of ∼1583 m² g^-1, making it a low-cost effective adsorbent for the removal of crystal violet dye, showing an adsorption capacity of 753.9 mg g^-1, optimal at 10 mg of adsorbent dose with only 10 min of contact time. It performed well in a wide pH range (2–12) and in saline solutions. Furthermore, the material demonstrated a single electrode specific capacitance of ∼155 F g^-1, an energy density of 21.6 Wh kg^-1, and a power density of 355.9 kW kg^-1 in supercapacitor applications. It exhibited high reversibility of charge-storage, retaining ∼85 % of its capacitance after 15,000 cycles. These results highlight the potential of pyrolyzed agricultural waste as a versatile and sustainable material for environmental and energy applications.