Carbon sequestration from high-BOD wastewater for efficient supercapacitor electrode

• AC from wastewater successfully sequestrated via hydrothermal carbonization. • Quinones-doped AC enhanced the electrochemical performance. • Specific capacitance of quinones-doped AC was 488.21 F g −1 . • Remarkable capacitance retention was 95.3 % after 1,000 charge–discharge cycles. • LEDs were lighted by symmetric supercapacitors using modified AC. Hydrothermal carbonization (HTC) is a promising techno-economic method for biomass waste valorization owing to its advantages over other thermochemical processes. This study focused on carbon sequestration from sugarcane bioethanol distillery wastewater via HTC and chemical activation to produce activated carbon (AC). The resulting AC was then applied as an active material for supercapacitor electrodes. The introduction of redox molecules, such as 1,4-anthraquinone and 9,10-phenanthrenequinone (PQ), on AC increased charge storage capability via redox transformation and enhanced the electrochemical performance of the supercapacitor electrode. Electrochemical testing showed that AC loaded with 16 wt% PQ achieved the highest specific capacitance of 488.21 F g −1 with remarkable capacitance retention of 95.3 % after 1000 charge–discharge cycles. N-doped AC obtained from the HTC of wastewater and melamine presented a slightly enhanced specific capacitance. Various commercial LEDs with a voltage range of 1.8–3.0 V were illuminated simultaneously by connecting them to two series of symmetric supercapacitors, demonstrating the potential application of our proposed strategy in energy storage systems. This study proposes a simple and efficient strategy to utilize wastewater and achieve net-zero emission goals in a Bio-Circular-Green Economy model.